Use compiler-agnostic defines to silence warning
[lttng-tools.git] / src / bin / lttng-sessiond / client.cpp
index 43201c71d5e0cb28ed5a5544886c755e3d694623..310b79f8b381dfb8884519049a187ef41dabd697 100644 (file)
 #include "clear.hpp"
 #include "client.hpp"
 #include "cmd.hpp"
-#include "common/buffer-view.hpp"
-#include "common/compat/socket.hpp"
-#include "common/dynamic-array.hpp"
-#include "common/dynamic-buffer.hpp"
-#include "common/fd-handle.hpp"
-#include "common/payload-view.hpp"
-#include "common/payload.hpp"
-#include "common/sessiond-comm/sessiond-comm.hpp"
 #include "health-sessiond.hpp"
 #include "kernel.hpp"
 #include "lttng-sessiond.hpp"
-#include "lttng/lttng-error.h"
-#include "lttng/tracker.h"
 #include "manage-consumer.hpp"
 #include "save.hpp"
 #include "testpoint.hpp"
 #include "utils.hpp"
 
+#include <common/buffer-view.hpp>
 #include <common/compat/getenv.hpp>
+#include <common/compat/socket.hpp>
+#include <common/dynamic-array.hpp>
+#include <common/dynamic-buffer.hpp>
+#include <common/exception.hpp>
+#include <common/fd-handle.hpp>
+#include <common/payload-view.hpp>
+#include <common/payload.hpp>
+#include <common/pthread-lock.hpp>
+#include <common/scope-exit.hpp>
+#include <common/sessiond-comm/sessiond-comm.hpp>
 #include <common/tracker.hpp>
 #include <common/unix.hpp>
 #include <common/utils.hpp>
 
 #include <lttng/error-query-internal.hpp>
 #include <lttng/event-internal.hpp>
+#include <lttng/lttng.h>
 #include <lttng/session-descriptor-internal.hpp>
 #include <lttng/session-internal.hpp>
 #include <lttng/userspace-probe-internal.hpp>
 
+#include <fcntl.h>
 #include <pthread.h>
 #include <signal.h>
 #include <stddef.h>
@@ -47,6 +50,8 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
+namespace ls = lttng::sessiond;
+
 namespace {
 bool is_root;
 
@@ -64,7 +69,7 @@ static void set_thread_status(bool running)
        sem_post(&thread_state.ready);
 }
 
-static bool wait_thread_status(void)
+static bool wait_thread_status()
 {
        DBG("Waiting for client thread to be ready");
        sem_wait(&thread_state.ready);
@@ -81,18 +86,15 @@ static bool wait_thread_status(void)
  * Setup the outgoing data buffer for the response (llm) by allocating the
  * right amount of memory and copying the original information from the lsm
  * structure.
- *
- * Return 0 on success, negative value on error.
  */
-static int setup_lttng_msg(struct command_ctx *cmd_ctx,
-                          const void *payload_buf,
-                          size_t payload_len,
-                          const void *cmd_header_buf,
-                          size_t cmd_header_len)
+static void setup_lttng_msg(struct command_ctx *cmd_ctx,
+                           const void *payload_buf,
+                           size_t payload_len,
+                           const void *cmd_header_buf,
+                           size_t cmd_header_len)
 {
-       int ret = 0;
-       const size_t header_len = sizeof(struct lttcomm_lttng_msg);
-       const size_t total_msg_size = header_len + cmd_header_len + payload_len;
+       const auto header_len = sizeof(struct lttcomm_lttng_msg);
+       const auto total_msg_size = header_len + cmd_header_len + payload_len;
        lttcomm_lttng_msg llm{};
 
        llm.cmd_type = cmd_ctx->lsm.cmd_type;
@@ -100,62 +102,53 @@ static int setup_lttng_msg(struct command_ctx *cmd_ctx,
        llm.cmd_header_size = (uint32_t) cmd_header_len;
        llm.data_size = (uint32_t) payload_len;
 
-       ret = lttng_dynamic_buffer_set_size(&cmd_ctx->reply_payload.buffer, 0);
-       if (ret) {
-               goto end;
-       }
+       const auto zero_ret = lttng_dynamic_buffer_set_size(&cmd_ctx->reply_payload.buffer, 0);
+       LTTNG_ASSERT(zero_ret == 0);
 
        lttng_dynamic_pointer_array_clear(&cmd_ctx->reply_payload._fd_handles);
 
        cmd_ctx->lttng_msg_size = total_msg_size;
 
        /* Append reply header. */
-       ret = lttng_dynamic_buffer_append(&cmd_ctx->reply_payload.buffer, &llm, sizeof(llm));
-       if (ret) {
-               goto end;
+       if (lttng_dynamic_buffer_append(&cmd_ctx->reply_payload.buffer, &llm, sizeof(llm))) {
+               LTTNG_THROW_ALLOCATION_FAILURE_ERROR(
+                       "Failed to append the reply header to a client reply", sizeof(llm));
        }
 
        /* Append command header. */
        if (cmd_header_len) {
-               ret = lttng_dynamic_buffer_append(
-                       &cmd_ctx->reply_payload.buffer, cmd_header_buf, cmd_header_len);
-               if (ret) {
-                       goto end;
+               if (lttng_dynamic_buffer_append(
+                           &cmd_ctx->reply_payload.buffer, cmd_header_buf, cmd_header_len)) {
+                       LTTNG_THROW_ALLOCATION_FAILURE_ERROR(
+                               "Failed to append the command header to a client reply",
+                               cmd_header_len);
                }
        }
 
        /* Append payload. */
        if (payload_len) {
-               ret = lttng_dynamic_buffer_append(
-                       &cmd_ctx->reply_payload.buffer, payload_buf, payload_len);
-               if (ret) {
-                       goto end;
+               if (lttng_dynamic_buffer_append(
+                           &cmd_ctx->reply_payload.buffer, payload_buf, payload_len)) {
+                       LTTNG_THROW_ALLOCATION_FAILURE_ERROR(
+                               "Failed to append the payload to a client reply", payload_len);
                }
        }
-
-end:
-       return ret;
 }
 
-static int setup_empty_lttng_msg(struct command_ctx *cmd_ctx)
+static void setup_empty_lttng_msg(struct command_ctx *cmd_ctx)
 {
-       int ret;
        const struct lttcomm_lttng_msg llm = {};
 
-       ret = lttng_dynamic_buffer_set_size(&cmd_ctx->reply_payload.buffer, 0);
-       if (ret) {
-               goto end;
-       }
+       const auto zero_ret = lttng_dynamic_buffer_set_size(&cmd_ctx->reply_payload.buffer, 0);
+       LTTNG_ASSERT(zero_ret == 0);
 
        /* Append place-holder reply header. */
-       ret = lttng_dynamic_buffer_append(&cmd_ctx->reply_payload.buffer, &llm, sizeof(llm));
-       if (ret) {
-               goto end;
+       if (lttng_dynamic_buffer_append(&cmd_ctx->reply_payload.buffer, &llm, sizeof(llm))) {
+               LTTNG_THROW_ALLOCATION_FAILURE_ERROR(
+                       "Failed to append the reply header to a client reply", sizeof(llm));
        }
 
        cmd_ctx->lttng_msg_size = sizeof(llm);
-end:
-       return ret;
 }
 
 static void update_lttng_msg(struct command_ctx *cmd_ctx, size_t cmd_header_len, size_t payload_len)
@@ -428,13 +421,12 @@ error:
  * function also applies the right modification on a per domain basis for the
  * trace files destination directory.
  */
-static int copy_session_consumer(int domain, struct ltt_session *session)
+static int copy_session_consumer(int domain, const ltt_session::locked_ref& session)
 {
        int ret;
        const char *dir_name;
        struct consumer_output *consumer;
 
-       LTTNG_ASSERT(session);
        LTTNG_ASSERT(session->consumer);
 
        switch (domain) {
@@ -456,6 +448,7 @@ static int copy_session_consumer(int domain, struct ltt_session *session)
                break;
        case LTTNG_DOMAIN_JUL:
        case LTTNG_DOMAIN_LOG4J:
+       case LTTNG_DOMAIN_LOG4J2:
        case LTTNG_DOMAIN_PYTHON:
        case LTTNG_DOMAIN_UST:
                DBG3("Copying tracing session consumer output in UST session");
@@ -488,18 +481,19 @@ error:
 /*
  * Create an UST session and add it to the session ust list.
  */
-static int create_ust_session(struct ltt_session *session, const struct lttng_domain *domain)
+static int create_ust_session(const ltt_session::locked_ref& session,
+                             const struct lttng_domain *domain)
 {
        int ret;
-       struct ltt_ust_session *lus = NULL;
+       struct ltt_ust_session *lus = nullptr;
 
-       LTTNG_ASSERT(session);
        LTTNG_ASSERT(domain);
        LTTNG_ASSERT(session->consumer);
 
        switch (domain->type) {
        case LTTNG_DOMAIN_JUL:
        case LTTNG_DOMAIN_LOG4J:
+       case LTTNG_DOMAIN_LOG4J2:
        case LTTNG_DOMAIN_PYTHON:
        case LTTNG_DOMAIN_UST:
                break;
@@ -512,7 +506,7 @@ static int create_ust_session(struct ltt_session *session, const struct lttng_do
        DBG("Creating UST session");
 
        lus = trace_ust_create_session(session->id);
-       if (lus == NULL) {
+       if (lus == nullptr) {
                ret = LTTNG_ERR_UST_SESS_FAIL;
                goto error;
        }
@@ -540,14 +534,14 @@ static int create_ust_session(struct ltt_session *session, const struct lttng_do
 
 error:
        free(lus);
-       session->ust_session = NULL;
+       session->ust_session = nullptr;
        return ret;
 }
 
 /*
  * Create a kernel tracer session then create the default channel.
  */
-static int create_kernel_session(struct ltt_session *session)
+static int create_kernel_session(const ltt_session::locked_ref& session)
 {
        int ret;
 
@@ -578,7 +572,7 @@ static int create_kernel_session(struct ltt_session *session)
 
 error:
        trace_kernel_destroy_session(session->kernel_session);
-       session->kernel_session = NULL;
+       session->kernel_session = nullptr;
 error_create:
        return ret;
 }
@@ -589,51 +583,50 @@ error_create:
 static unsigned int lttng_sessions_count(uid_t uid, gid_t gid __attribute__((unused)))
 {
        unsigned int i = 0;
-       struct ltt_session *session;
        const struct ltt_session_list *session_list = session_get_list();
 
        DBG("Counting number of available session for UID %d", uid);
-       cds_list_for_each_entry (session, &session_list->head, list) {
-               if (!session_get(session)) {
-                       continue;
-               }
-               session_lock(session);
+       for (auto *raw_session_ptr :
+            lttng::urcu::list_iteration_adapter<ltt_session, &ltt_session::list>(
+                    session_list->head)) {
+               auto session = [raw_session_ptr]() {
+                       session_get(raw_session_ptr);
+                       raw_session_ptr->lock();
+                       return ltt_session::make_locked_ref(*raw_session_ptr);
+               }();
+
                /* Only count the sessions the user can control. */
                if (session_access_ok(session, uid) && !session->destroyed) {
                        i++;
                }
-               session_unlock(session);
-               session_put(session);
        }
+
        return i;
 }
 
-static enum lttng_error_code receive_lttng_trigger(struct command_ctx *cmd_ctx,
-                                                  int sock,
-                                                  int *sock_error,
-                                                  struct lttng_trigger **_trigger)
+static lttng::ctl::trigger
+receive_lttng_trigger(struct command_ctx *cmd_ctx, int sock, int *sock_error)
 {
        int ret;
        size_t trigger_len;
        ssize_t sock_recv_len;
-       enum lttng_error_code ret_code;
        struct lttng_payload trigger_payload;
-       struct lttng_trigger *trigger = NULL;
+       struct lttng_trigger *trigger = nullptr;
 
        lttng_payload_init(&trigger_payload);
+       const auto reset_payload_on_exit = lttng::make_scope_exit(
+               [&trigger_payload]() noexcept { lttng_payload_reset(&trigger_payload); });
+
        trigger_len = (size_t) cmd_ctx->lsm.u.trigger.length;
        ret = lttng_dynamic_buffer_set_size(&trigger_payload.buffer, trigger_len);
        if (ret) {
-               ret_code = LTTNG_ERR_NOMEM;
-               goto end;
+               LTTNG_THROW_CTL("Failed to allocate buffer for trigger receptio", LTTNG_ERR_NOMEM);
        }
 
        sock_recv_len = lttcomm_recv_unix_sock(sock, trigger_payload.buffer.data, trigger_len);
        if (sock_recv_len < 0 || sock_recv_len != trigger_len) {
-               ERR("Failed to receive trigger in command payload");
                *sock_error = 1;
-               ret_code = LTTNG_ERR_INVALID_PROTOCOL;
-               goto end;
+               LTTNG_THROW_PROTOCOL_ERROR("Failed to receive trigger in command payload");
        }
 
        /* Receive fds, if any. */
@@ -641,19 +634,17 @@ static enum lttng_error_code receive_lttng_trigger(struct command_ctx *cmd_ctx,
                sock_recv_len = lttcomm_recv_payload_fds_unix_sock(
                        sock, cmd_ctx->lsm.fd_count, &trigger_payload);
                if (sock_recv_len > 0 && sock_recv_len != cmd_ctx->lsm.fd_count * sizeof(int)) {
-                       ERR("Failed to receive all file descriptors for trigger in command payload: expected fd count = %u, ret = %d",
-                           cmd_ctx->lsm.fd_count,
-                           (int) ret);
-                       ret_code = LTTNG_ERR_INVALID_PROTOCOL;
                        *sock_error = 1;
-                       goto end;
+                       LTTNG_THROW_PROTOCOL_ERROR(fmt::format(
+                               "Failed to receive all file descriptors for trigger in command payload: expected_fd_count={}, ret={}",
+                               [cmd_ctx]() { return cmd_ctx->lsm.fd_count; }(),
+                               sock_recv_len));
                } else if (sock_recv_len <= 0) {
-                       ERR("Failed to receive file descriptors for trigger in command payload: expected fd count = %u, ret = %d",
-                           cmd_ctx->lsm.fd_count,
-                           (int) ret);
-                       ret_code = LTTNG_ERR_FATAL;
                        *sock_error = 1;
-                       goto end;
+                       LTTNG_THROW_PROTOCOL_ERROR(fmt::format(
+                               "Failed to receive file descriptors for trigger in command payload: expected_fd_count={}, ret={}",
+                               [cmd_ctx]() { return cmd_ctx->lsm.fd_count; }(),
+                               sock_recv_len));
                }
        }
 
@@ -662,20 +653,20 @@ static enum lttng_error_code receive_lttng_trigger(struct command_ctx *cmd_ctx,
                struct lttng_payload_view view =
                        lttng_payload_view_from_payload(&trigger_payload, 0, -1);
 
-               if (lttng_trigger_create_from_payload(&view, &trigger) != trigger_len) {
-                       ERR("Invalid trigger received as part of command payload");
-                       ret_code = LTTNG_ERR_INVALID_TRIGGER;
+               const auto trigger_create_ret = lttng_trigger_create_from_payload(&view, &trigger);
+
+               if (trigger_create_ret != trigger_len) {
                        lttng_trigger_put(trigger);
-                       goto end;
+                       LTTNG_THROW_PROTOCOL_ERROR(fmt::format(
+                               "Trigger of unexpected size received as part of command payload: expected_size={}, actual_size={}",
+                               trigger_len,
+                               trigger_create_ret));
+               } else if (trigger_create_ret < 0) {
+                       LTTNG_THROW_CTL("Failed to allocate trigger", LTTNG_ERR_NOMEM);
                }
        }
 
-       *_trigger = trigger;
-       ret_code = LTTNG_OK;
-
-end:
-       lttng_payload_reset(&trigger_payload);
-       return ret_code;
+       return lttng::ctl::trigger(trigger);
 }
 
 static enum lttng_error_code receive_lttng_error_query(struct command_ctx *cmd_ctx,
@@ -688,7 +679,7 @@ static enum lttng_error_code receive_lttng_error_query(struct command_ctx *cmd_c
        ssize_t sock_recv_len;
        enum lttng_error_code ret_code;
        struct lttng_payload query_payload;
-       struct lttng_error_query *query = NULL;
+       struct lttng_error_query *query = nullptr;
 
        lttng_payload_init(&query_payload);
        query_len = (size_t) cmd_ctx->lsm.u.error_query.length;
@@ -760,10 +751,10 @@ static enum lttng_error_code receive_lttng_event(struct command_ctx *cmd_ctx,
        ssize_t sock_recv_len;
        enum lttng_error_code ret_code;
        struct lttng_payload event_payload;
-       struct lttng_event *local_event = NULL;
-       char *local_filter_expression = NULL;
-       struct lttng_bytecode *local_bytecode = NULL;
-       struct lttng_event_exclusion *local_exclusion = NULL;
+       struct lttng_event *local_event = nullptr;
+       char *local_filter_expression = nullptr;
+       struct lttng_bytecode *local_bytecode = nullptr;
+       struct lttng_event_exclusion *local_exclusion = nullptr;
 
        lttng_payload_init(&event_payload);
        if (cmd_ctx->lsm.cmd_type == LTTCOMM_SESSIOND_COMMAND_ENABLE_EVENT) {
@@ -841,10 +832,10 @@ static enum lttng_error_code receive_lttng_event(struct command_ctx *cmd_ctx,
        *out_exclusion = local_exclusion;
        *out_filter_expression = local_filter_expression;
        *out_bytecode = local_bytecode;
-       local_event = NULL;
-       local_exclusion = NULL;
-       local_filter_expression = NULL;
-       local_bytecode = NULL;
+       local_event = nullptr;
+       local_exclusion = nullptr;
+       local_filter_expression = nullptr;
+       local_bytecode = nullptr;
 
        ret_code = LTTNG_OK;
 
@@ -868,7 +859,7 @@ receive_lttng_event_context(const struct command_ctx *cmd_ctx,
        ssize_t sock_recv_len;
        enum lttng_error_code ret_code;
        struct lttng_payload event_context_payload;
-       struct lttng_event_context *context = NULL;
+       struct lttng_event_context *context = nullptr;
 
        lttng_payload_init(&event_context_payload);
 
@@ -911,7 +902,7 @@ receive_lttng_event_context(const struct command_ctx *cmd_ctx,
        }
 
        *out_event_context = context;
-       context = NULL;
+       context = nullptr;
        ret_code = LTTNG_OK;
 
 end:
@@ -923,17 +914,17 @@ end:
 /*
  * Version of setup_lttng_msg() without command header.
  */
-static int
+static void
 setup_lttng_msg_no_cmd_header(struct command_ctx *cmd_ctx, void *payload_buf, size_t payload_len)
 {
-       return setup_lttng_msg(cmd_ctx, payload_buf, payload_len, NULL, 0);
+       setup_lttng_msg(cmd_ctx, payload_buf, payload_len, nullptr, 0);
 }
 
 /*
  * Check if the current kernel tracer supports the session rotation feature.
  * Return 1 if it does, 0 otherwise.
  */
-static int check_rotate_compatible(void)
+static int check_rotate_compatible()
 {
        int ret = 1;
 
@@ -977,6 +968,12 @@ end:
        return ret;
 }
 
+static void command_ctx_set_status_code(command_ctx& cmd_ctx, enum lttng_error_code status_code)
+{
+       LTTNG_ASSERT(cmd_ctx.reply_payload.buffer.size >= sizeof(lttcomm_lttng_msg));
+       ((struct lttcomm_lttng_msg *) (cmd_ctx.reply_payload.buffer.data))->ret_code = status_code;
+}
+
 /*
  * Process the command requested by the lttng client within the command
  * context structure. This function make sure that the return structure (llm)
@@ -996,15 +993,15 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
        bool need_consumerd;
 
        if (!lttcomm_sessiond_command_is_valid((lttcomm_sessiond_command) cmd_ctx->lsm.cmd_type)) {
-               ERR("Unknown client command received: command id = %" PRIu32,
-                   cmd_ctx->lsm.cmd_type);
-               ret = LTTNG_ERR_UND;
-               goto error;
+               /* The lambda is used since fmt can't bind a packed field. */
+               LTTNG_THROW_CTL(fmt::format("Unknown client command: command_id={}",
+                                           [&cmd_ctx]() { return cmd_ctx->lsm.cmd_type; }()),
+                               LTTNG_ERR_UND);
        }
 
-       DBG("Processing client command '%s\' (%d)",
-           lttcomm_sessiond_command_str((lttcomm_sessiond_command) cmd_ctx->lsm.cmd_type),
-           cmd_ctx->lsm.cmd_type);
+       DBG_FMT("Processing client command: name=`{}`, id={}",
+               lttcomm_sessiond_command_str((lttcomm_sessiond_command) cmd_ctx->lsm.cmd_type),
+               [&cmd_ctx]() { return cmd_ctx->lsm.cmd_type; }());
 
        *sock_error = 0;
 
@@ -1031,6 +1028,7 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
        case LTTCOMM_SESSIOND_COMMAND_CLEAR_SESSION:
        case LTTCOMM_SESSIOND_COMMAND_LIST_TRIGGERS:
        case LTTCOMM_SESSIOND_COMMAND_EXECUTE_ERROR_QUERY:
+       case LTTCOMM_SESSIOND_COMMAND_KERNEL_TRACER_STATUS:
                need_domain = false;
                break;
        default:
@@ -1052,22 +1050,25 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
        if (the_config.no_kernel && need_domain &&
            cmd_ctx->lsm.domain.type == LTTNG_DOMAIN_KERNEL) {
                if (!is_root) {
-                       ret = LTTNG_ERR_NEED_ROOT_SESSIOND;
+                       LTTNG_THROW_CTL(
+                               "Can't run a kernel-domain command since the session daemon is not running as root",
+                               LTTNG_ERR_NEED_ROOT_SESSIOND);
                } else {
-                       ret = LTTNG_ERR_KERN_NA;
+                       LTTNG_THROW_CTL(
+                               "Can't run a kernel-domain command since kernel tracing is disabled",
+                               LTTNG_ERR_KERN_NA);
                }
-               goto error;
        }
 
        /* Deny register consumer if we already have a spawned consumer. */
        if (cmd_ctx->lsm.cmd_type == LTTCOMM_SESSIOND_COMMAND_REGISTER_CONSUMER) {
-               pthread_mutex_lock(&the_kconsumer_data.pid_mutex);
+               const lttng::pthread::lock_guard kconsumer_lock(the_kconsumer_data.pid_mutex);
+
                if (the_kconsumer_data.pid > 0) {
-                       ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
-                       pthread_mutex_unlock(&the_kconsumer_data.pid_mutex);
-                       goto error;
+                       LTTNG_THROW_CTL(
+                               "Can't register a consumer since a kernel-domain consumer was already launched",
+                               LTTNG_ERR_KERN_CONSUMER_FAIL);
                }
-               pthread_mutex_unlock(&the_kconsumer_data.pid_mutex);
        }
 
        /*
@@ -1095,13 +1096,29 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
                break;
        default:
                /* Setup lttng message with no payload */
-               ret = setup_lttng_msg_no_cmd_header(cmd_ctx, NULL, 0);
-               if (ret < 0) {
-                       /* This label does not try to unlock the session */
-                       goto init_setup_error;
-               }
+               setup_lttng_msg_no_cmd_header(cmd_ctx, nullptr, 0);
        }
 
+       /*
+        * The list lock is only acquired when processing a command that is applied
+        * against a session. As such, a unique_lock that holds the list lock is move()'d to
+        * list_lock during the execution of those commands. The list lock is then released
+        * as the instance leaves this scope.
+        *
+        * Mind the order of the declaration of list_lock vs target_session:
+        * the session list lock must always be released _after_ the release of
+        * a session's reference (the destruction of a ref/locked_ref) to ensure
+        * since the reference's release may unpublish the session from the list of
+        * sessions.
+        */
+       std::unique_lock<std::mutex> list_lock;
+       /*
+        * A locked_ref is typically "never null" (hence its name). However, due to the
+        * structure of this function, target_session remains unset for commands that don't
+        * have a target session.
+        */
+       nonstd::optional<ltt_session::locked_ref> target_session;
+
        /* Commands that DO NOT need a session. */
        switch (cmd_ctx->lsm.cmd_type) {
        case LTTCOMM_SESSIOND_COMMAND_CREATE_SESSION_EXT:
@@ -1114,24 +1131,37 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
        case LTTCOMM_SESSIOND_COMMAND_UNREGISTER_TRIGGER:
        case LTTCOMM_SESSIOND_COMMAND_LIST_TRIGGERS:
        case LTTCOMM_SESSIOND_COMMAND_EXECUTE_ERROR_QUERY:
+       case LTTCOMM_SESSIOND_COMMAND_KERNEL_TRACER_STATUS:
                need_tracing_session = false;
                break;
        default:
+               if (strnlen(cmd_ctx->lsm.session.name, sizeof(cmd_ctx->lsm.session.name)) ==
+                   sizeof(cmd_ctx->lsm.session.name)) {
+                       LTTNG_THROW_INVALID_ARGUMENT_ERROR(
+                               "Session name received from lttng-ctl client is not null-terminated");
+               }
+
                DBG("Getting session %s by name", cmd_ctx->lsm.session.name);
                /*
                 * We keep the session list lock across _all_ commands
                 * for now, because the per-session lock does not
                 * handle teardown properly.
                 */
-               session_lock_list();
-               cmd_ctx->session = session_find_by_name(cmd_ctx->lsm.session.name);
-               if (cmd_ctx->session == NULL) {
-                       ret = LTTNG_ERR_SESS_NOT_FOUND;
-                       goto error;
-               } else {
-                       /* Acquire lock for the session */
-                       session_lock(cmd_ctx->session);
-               }
+               list_lock = lttng::sessiond::lock_session_list();
+               try {
+                       target_session.emplace(
+                               ltt_session::find_locked_session(cmd_ctx->lsm.session.name));
+               } catch (...) {
+                       std::throw_with_nested(lttng::ctl::error(
+                               fmt::format(
+                                       "Target session of command doesn't exist: command='{}'",
+                                       lttcomm_sessiond_command_str(
+                                               (lttcomm_sessiond_command) cmd_ctx->lsm.cmd_type)),
+                               LTTNG_ERR_SESS_NOT_FOUND,
+                               LTTNG_SOURCE_LOCATION()));
+               }
+
+               LTTNG_ASSERT(target_session);
                break;
        }
 
@@ -1146,17 +1176,17 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
        case LTTCOMM_SESSIOND_COMMAND_DISABLE_EVENT:
                switch (cmd_ctx->lsm.domain.type) {
                case LTTNG_DOMAIN_KERNEL:
-                       if (!cmd_ctx->session->kernel_session) {
-                               ret = LTTNG_ERR_NO_CHANNEL;
-                               goto error;
+                       if (!(*target_session)->kernel_session) {
+                               return LTTNG_ERR_NO_CHANNEL;
                        }
                        break;
                case LTTNG_DOMAIN_JUL:
                case LTTNG_DOMAIN_LOG4J:
+               case LTTNG_DOMAIN_LOG4J2:
                case LTTNG_DOMAIN_PYTHON:
                case LTTNG_DOMAIN_UST:
-                       if (!cmd_ctx->session->ust_session) {
-                               ret = LTTNG_ERR_NO_CHANNEL;
+                       if (!(*target_session)->ust_session) {
+                               return LTTNG_ERR_NO_CHANNEL;
                                goto error;
                        }
                        break;
@@ -1199,8 +1229,8 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
 
                /* Need a session for kernel command */
                if (need_tracing_session) {
-                       if (cmd_ctx->session->kernel_session == NULL) {
-                               ret = create_kernel_session(cmd_ctx->session);
+                       if ((*target_session)->kernel_session == nullptr) {
+                               ret = create_kernel_session(*target_session);
                                if (ret != LTTNG_OK) {
                                        ret = LTTNG_ERR_KERN_SESS_FAIL;
                                        goto error;
@@ -1227,7 +1257,7 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
                         * the consumer output of the session if exist.
                         */
                        ret = consumer_create_socket(&the_kconsumer_data,
-                                                    cmd_ctx->session->kernel_session->consumer);
+                                                    (*target_session)->kernel_session->consumer);
                        if (ret < 0) {
                                goto error;
                        }
@@ -1236,6 +1266,7 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
                break;
        case LTTNG_DOMAIN_JUL:
        case LTTNG_DOMAIN_LOG4J:
+       case LTTNG_DOMAIN_LOG4J2:
        case LTTNG_DOMAIN_PYTHON:
                if (!agent_tracing_is_enabled()) {
                        ret = LTTNG_ERR_AGENT_TRACING_DISABLED;
@@ -1257,9 +1288,9 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
 
                if (need_tracing_session) {
                        /* Create UST session if none exist. */
-                       if (cmd_ctx->session->ust_session == NULL) {
-                               lttng_domain domain = cmd_ctx->lsm.domain;
-                               ret = create_ust_session(cmd_ctx->session, &domain);
+                       if ((*target_session)->ust_session == nullptr) {
+                               const lttng_domain domain = cmd_ctx->lsm.domain;
+                               ret = create_ust_session(*target_session, &domain);
                                if (ret != LTTNG_OK) {
                                        goto error;
                                }
@@ -1291,7 +1322,7 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
                         * since it was set above and can ONLY be set in this thread.
                         */
                        ret = consumer_create_socket(&the_ustconsumer64_data,
-                                                    cmd_ctx->session->ust_session->consumer);
+                                                    (*target_session)->ust_session->consumer);
                        if (ret < 0) {
                                goto error;
                        }
@@ -1321,7 +1352,7 @@ static int process_client_msg(struct command_ctx *cmd_ctx, int *sock, int *sock_
                         * since it was set above and can ONLY be set in this thread.
                         */
                        ret = consumer_create_socket(&the_ustconsumer32_data,
-                                                    cmd_ctx->session->ust_session->consumer);
+                                                    (*target_session)->ust_session->consumer);
                        if (ret < 0) {
                                goto error;
                        }
@@ -1341,6 +1372,7 @@ skip_domain:
                        break;
                case LTTNG_DOMAIN_JUL:
                case LTTNG_DOMAIN_LOG4J:
+               case LTTNG_DOMAIN_LOG4J2:
                case LTTNG_DOMAIN_PYTHON:
                case LTTNG_DOMAIN_UST:
                        if (uatomic_read(&the_ust_consumerd_state) != CONSUMER_STARTED) {
@@ -1365,9 +1397,8 @@ skip_domain:
         * The root user can interact with all sessions.
         */
        if (need_tracing_session) {
-               if (!session_access_ok(cmd_ctx->session,
-                                      LTTNG_SOCK_GET_UID_CRED(&cmd_ctx->creds)) ||
-                   cmd_ctx->session->destroyed) {
+               if (!session_access_ok(*target_session, LTTNG_SOCK_GET_UID_CRED(&cmd_ctx->creds)) ||
+                   (*target_session)->destroyed) {
                        ret = LTTNG_ERR_EPERM;
                        goto error;
                }
@@ -1377,12 +1408,12 @@ skip_domain:
         * Send relayd information to consumer as soon as we have a domain and a
         * session defined.
         */
-       if (cmd_ctx->session && need_domain) {
+       if (target_session && need_domain) {
                /*
                 * Setup relayd if not done yet. If the relayd information was already
                 * sent to the consumer, this call will gracefully return.
                 */
-               ret = cmd_setup_relayd(cmd_ctx->session);
+               ret = cmd_setup_relayd(*target_session);
                if (ret != LTTNG_OK) {
                        goto error;
                }
@@ -1392,7 +1423,7 @@ skip_domain:
        switch (cmd_ctx->lsm.cmd_type) {
        case LTTCOMM_SESSIOND_COMMAND_ADD_CONTEXT:
        {
-               struct lttng_event_context *event_context = NULL;
+               struct lttng_event_context *event_context = nullptr;
                const enum lttng_error_code ret_code =
                        receive_lttng_event_context(cmd_ctx, *sock, sock_error, &event_context);
 
@@ -1401,20 +1432,21 @@ skip_domain:
                        goto error;
                }
 
-               ret = cmd_add_context(cmd_ctx, event_context, the_kernel_poll_pipe[1]);
+               ret = cmd_add_context(
+                       cmd_ctx, *target_session, event_context, the_kernel_poll_pipe[1]);
                lttng_event_context_destroy(event_context);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_DISABLE_CHANNEL:
        {
-               ret = cmd_disable_channel(cmd_ctx->session,
+               ret = cmd_disable_channel(*target_session,
                                          cmd_ctx->lsm.domain.type,
                                          cmd_ctx->lsm.u.disable.channel_name);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_ENABLE_CHANNEL:
        {
-               ret = cmd_enable_channel(cmd_ctx, *sock, the_kernel_poll_pipe[1]);
+               ret = cmd_enable_channel(cmd_ctx, *target_session, *sock, the_kernel_poll_pipe[1]);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_PROCESS_ATTR_TRACKER_ADD_INCLUDE_VALUE:
@@ -1511,10 +1543,10 @@ skip_domain:
 
                if (add_value) {
                        ret = cmd_process_attr_tracker_inclusion_set_add_value(
-                               cmd_ctx->session, domain_type, process_attr, value);
+                               *target_session, domain_type, process_attr, value);
                } else {
                        ret = cmd_process_attr_tracker_inclusion_set_remove_value(
-                               cmd_ctx->session, domain_type, process_attr, value);
+                               *target_session, domain_type, process_attr, value);
                }
                process_attr_value_destroy(value);
        error_add_remove_tracker_value:
@@ -1531,18 +1563,14 @@ skip_domain:
                                .process_attr_tracker_get_tracking_policy.process_attr;
 
                ret = cmd_process_attr_tracker_get_tracking_policy(
-                       cmd_ctx->session, domain_type, process_attr, &tracking_policy);
+                       *target_session, domain_type, process_attr, &tracking_policy);
                if (ret != LTTNG_OK) {
                        goto error;
                }
 
                uint32_t tracking_policy_u32 = tracking_policy;
-               ret = setup_lttng_msg_no_cmd_header(
-                       cmd_ctx, &tracking_policy_u32, sizeof(uint32_t));
-               if (ret < 0) {
-                       ret = LTTNG_ERR_NOMEM;
-                       goto error;
-               }
+               setup_lttng_msg_no_cmd_header(cmd_ctx, &tracking_policy_u32, sizeof(uint32_t));
+
                ret = LTTNG_OK;
                break;
        }
@@ -1558,7 +1586,7 @@ skip_domain:
                                .process_attr_tracker_set_tracking_policy.process_attr;
 
                ret = cmd_process_attr_tracker_set_tracking_policy(
-                       cmd_ctx->session, domain_type, process_attr, tracking_policy);
+                       *target_session, domain_type, process_attr, tracking_policy);
                if (ret != LTTNG_OK) {
                        goto error;
                }
@@ -1575,7 +1603,7 @@ skip_domain:
                                cmd_ctx->lsm.u.process_attr_tracker_get_inclusion_set.process_attr;
 
                ret = cmd_process_attr_tracker_get_inclusion_set(
-                       cmd_ctx->session, domain_type, process_attr, &values);
+                       *target_session, domain_type, process_attr, &values);
                if (ret != LTTNG_OK) {
                        goto error;
                }
@@ -1586,11 +1614,7 @@ skip_domain:
                        goto error_tracker_get_inclusion_set;
                }
 
-               ret = setup_lttng_msg_no_cmd_header(cmd_ctx, reply.data, reply.size);
-               if (ret < 0) {
-                       ret = LTTNG_ERR_NOMEM;
-                       goto error_tracker_get_inclusion_set;
-               }
+               setup_lttng_msg_no_cmd_header(cmd_ctx, reply.data, reply.size);
                ret = LTTNG_OK;
 
        error_tracker_get_inclusion_set:
@@ -1624,12 +1648,18 @@ skip_domain:
                 */
                ret = cmd_ctx->lsm.cmd_type == LTTCOMM_SESSIOND_COMMAND_ENABLE_EVENT ?
                        cmd_enable_event(cmd_ctx,
+                                        *target_session,
                                         event,
                                         filter_expression,
                                         exclusions,
                                         bytecode,
                                         the_kernel_poll_pipe[1]) :
-                       cmd_disable_event(cmd_ctx, event, filter_expression, bytecode, exclusions);
+                       cmd_disable_event(cmd_ctx,
+                                         *target_session,
+                                         event,
+                                         filter_expression,
+                                         bytecode,
+                                         exclusions);
                lttng_event_destroy(event);
                break;
        }
@@ -1640,17 +1670,12 @@ skip_domain:
                size_t payload_size;
                const size_t command_header_size = sizeof(struct lttcomm_list_command_header);
 
-               ret = setup_empty_lttng_msg(cmd_ctx);
-               if (ret) {
-                       ret = LTTNG_ERR_NOMEM;
-                       goto setup_error;
-               }
+               setup_empty_lttng_msg(cmd_ctx);
 
                original_payload_size = cmd_ctx->reply_payload.buffer.size;
 
-               session_lock_list();
+               list_lock = lttng::sessiond::lock_session_list();
                ret_code = cmd_list_tracepoints(cmd_ctx->lsm.domain.type, &cmd_ctx->reply_payload);
-               session_unlock_list();
                if (ret_code != LTTNG_OK) {
                        ret = (int) ret_code;
                        goto error;
@@ -1670,18 +1695,14 @@ skip_domain:
                size_t payload_size;
                const size_t command_header_size = sizeof(struct lttcomm_list_command_header);
 
-               ret = setup_empty_lttng_msg(cmd_ctx);
-               if (ret) {
-                       ret = LTTNG_ERR_NOMEM;
-                       goto setup_error;
-               }
+               setup_empty_lttng_msg(cmd_ctx);
 
                original_payload_size = cmd_ctx->reply_payload.buffer.size;
 
-               session_lock_list();
+               list_lock = lttng::sessiond::lock_session_list();
                ret_code = cmd_list_tracepoint_fields(cmd_ctx->lsm.domain.type,
                                                      &cmd_ctx->reply_payload);
-               session_unlock_list();
+
                if (ret_code != LTTNG_OK) {
                        ret = (int) ret_code;
                        goto error;
@@ -1701,11 +1722,7 @@ skip_domain:
                size_t payload_size;
                const size_t command_header_size = sizeof(struct lttcomm_list_command_header);
 
-               ret = setup_empty_lttng_msg(cmd_ctx);
-               if (ret) {
-                       ret = LTTNG_ERR_NOMEM;
-                       goto setup_error;
-               }
+               setup_empty_lttng_msg(cmd_ctx);
 
                original_payload_size = cmd_ctx->reply_payload.buffer.size;
 
@@ -1736,7 +1753,7 @@ skip_domain:
                }
 
                uris = calloc<lttng_uri>(nb_uri);
-               if (uris == NULL) {
+               if (uris == nullptr) {
                        ret = LTTNG_ERR_FATAL;
                        goto error;
                }
@@ -1752,7 +1769,7 @@ skip_domain:
                        goto error;
                }
 
-               ret = cmd_set_consumer_uri(cmd_ctx->session, nb_uri, uris);
+               ret = cmd_set_consumer_uri(*target_session, nb_uri, uris);
                free(uris);
                if (ret != LTTNG_OK) {
                        goto error;
@@ -1767,46 +1784,42 @@ skip_domain:
                 * enabled time or size-based rotations, we have to make sure
                 * the kernel tracer supports it.
                 */
-               if (!cmd_ctx->session->has_been_started && cmd_ctx->session->kernel_session &&
-                   (cmd_ctx->session->rotate_timer_period || cmd_ctx->session->rotate_size) &&
+               if (!(*target_session)->has_been_started && (*target_session)->kernel_session &&
+                   ((*target_session)->rotate_timer_period || (*target_session)->rotate_size) &&
                    !check_rotate_compatible()) {
                        DBG("Kernel tracer version is not compatible with the rotation feature");
                        ret = LTTNG_ERR_ROTATION_WRONG_VERSION;
                        goto error;
                }
-               ret = cmd_start_trace(cmd_ctx->session);
+               ret = cmd_start_trace(*target_session);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_STOP_TRACE:
        {
-               ret = cmd_stop_trace(cmd_ctx->session);
+               ret = cmd_stop_trace(*target_session);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_DESTROY_SESSION:
        {
-               ret = cmd_destroy_session(cmd_ctx->session, the_notification_thread_handle, sock);
+               ret = cmd_destroy_session(*target_session, sock);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_LIST_DOMAINS:
        {
                ssize_t nb_dom;
-               struct lttng_domain *domains = NULL;
+               struct lttng_domain *domains = nullptr;
 
-               nb_dom = cmd_list_domains(cmd_ctx->session, &domains);
+               nb_dom = cmd_list_domains(*target_session, &domains);
                if (nb_dom < 0) {
                        /* Return value is a negative lttng_error_code. */
                        ret = -nb_dom;
                        goto error;
                }
 
-               ret = setup_lttng_msg_no_cmd_header(
+               setup_lttng_msg_no_cmd_header(
                        cmd_ctx, domains, nb_dom * sizeof(struct lttng_domain));
                free(domains);
 
-               if (ret < 0) {
-                       goto setup_error;
-               }
-
                ret = LTTNG_OK;
                break;
        }
@@ -1817,16 +1830,12 @@ skip_domain:
                size_t payload_size;
                const size_t command_header_size = sizeof(struct lttcomm_list_command_header);
 
-               ret = setup_empty_lttng_msg(cmd_ctx);
-               if (ret) {
-                       ret = LTTNG_ERR_NOMEM;
-                       goto setup_error;
-               }
+               setup_empty_lttng_msg(cmd_ctx);
 
                original_payload_size = cmd_ctx->reply_payload.buffer.size;
 
                ret_code = cmd_list_channels(
-                       cmd_ctx->lsm.domain.type, cmd_ctx->session, &cmd_ctx->reply_payload);
+                       cmd_ctx->lsm.domain.type, *target_session, &cmd_ctx->reply_payload);
                if (ret_code != LTTNG_OK) {
                        ret = (int) ret_code;
                        goto error;
@@ -1846,16 +1855,12 @@ skip_domain:
                size_t payload_size;
                const size_t command_header_size = sizeof(struct lttcomm_list_command_header);
 
-               ret = setup_empty_lttng_msg(cmd_ctx);
-               if (ret) {
-                       ret = LTTNG_ERR_NOMEM;
-                       goto setup_error;
-               }
+               setup_empty_lttng_msg(cmd_ctx);
 
                original_payload_size = cmd_ctx->reply_payload.buffer.size;
 
                ret_code = cmd_list_events(cmd_ctx->lsm.domain.type,
-                                          cmd_ctx->session,
+                                          *target_session,
                                           cmd_ctx->lsm.u.list.channel_name,
                                           &cmd_ctx->reply_payload);
                if (ret_code != LTTNG_OK) {
@@ -1876,7 +1881,7 @@ skip_domain:
                lttng_session *sessions_payload = nullptr;
                size_t payload_len = 0;
 
-               session_lock_list();
+               list_lock = lttng::sessiond::lock_session_list();
                nr_sessions = lttng_sessions_count(LTTNG_SOCK_GET_UID_CRED(&cmd_ctx->creds),
                                                   LTTNG_SOCK_GET_GID_CRED(&cmd_ctx->creds));
 
@@ -1885,9 +1890,9 @@ skip_domain:
                                (sizeof(struct lttng_session_extended) * nr_sessions);
                        sessions_payload = zmalloc<lttng_session>(payload_len);
                        if (!sessions_payload) {
-                               session_unlock_list();
-                               ret = -ENOMEM;
-                               goto setup_error;
+                               LTTNG_THROW_ALLOCATION_FAILURE_ERROR(
+                                       "Failed to allocate session list reply payload",
+                                       payload_len);
                        }
 
                        cmd_list_lttng_sessions(sessions_payload,
@@ -1896,15 +1901,9 @@ skip_domain:
                                                LTTNG_SOCK_GET_GID_CRED(&cmd_ctx->creds));
                }
 
-               session_unlock_list();
-
-               ret = setup_lttng_msg_no_cmd_header(cmd_ctx, sessions_payload, payload_len);
+               setup_lttng_msg_no_cmd_header(cmd_ctx, sessions_payload, payload_len);
                free(sessions_payload);
 
-               if (ret < 0) {
-                       goto setup_error;
-               }
-
                ret = LTTNG_OK;
                break;
        }
@@ -1922,7 +1921,23 @@ skip_domain:
                }
 
                ret = cmd_register_consumer(
-                       cmd_ctx->session, cmd_ctx->lsm.domain.type, cmd_ctx->lsm.u.reg.path, cdata);
+                       *target_session, cmd_ctx->lsm.domain.type, cmd_ctx->lsm.u.reg.path, cdata);
+               break;
+       }
+       case LTTCOMM_SESSIOND_COMMAND_KERNEL_TRACER_STATUS:
+       {
+               uint32_t u_status;
+               enum lttng_kernel_tracer_status status;
+
+               ret = cmd_kernel_tracer_status(&status);
+               if (ret != LTTNG_OK) {
+                       goto error;
+               }
+
+               u_status = (uint32_t) status;
+               setup_lttng_msg_no_cmd_header(cmd_ctx, &u_status, 4);
+
+               ret = LTTNG_OK;
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_DATA_PENDING:
@@ -1930,7 +1945,7 @@ skip_domain:
                int pending_ret;
                uint8_t pending_ret_byte;
 
-               pending_ret = cmd_data_pending(cmd_ctx->session);
+               pending_ret = cmd_data_pending(*target_session);
 
                /*
                 * FIXME
@@ -1946,22 +1961,18 @@ skip_domain:
                         * ret will be set to LTTNG_OK at the end of
                         * this function.
                         */
-               } else if (pending_ret < 0) {
+               } else if (pending_ret <= LTTNG_OK || pending_ret >= LTTNG_ERR_NR) {
                        ret = LTTNG_ERR_UNK;
-                       goto setup_error;
+                       goto error;
                } else {
                        ret = pending_ret;
-                       goto setup_error;
+                       goto error;
                }
 
                pending_ret_byte = (uint8_t) pending_ret;
 
                /* 1 byte to return whether or not data is pending */
-               ret = setup_lttng_msg_no_cmd_header(cmd_ctx, &pending_ret_byte, 1);
-
-               if (ret < 0) {
-                       goto setup_error;
-               }
+               setup_lttng_msg_no_cmd_header(cmd_ctx, &pending_ret_byte, 1);
 
                ret = LTTNG_OK;
                break;
@@ -1970,18 +1981,15 @@ skip_domain:
        {
                uint32_t snapshot_id;
                struct lttcomm_lttng_output_id reply;
-               lttng_snapshot_output output = cmd_ctx->lsm.u.snapshot_output.output;
+               const lttng_snapshot_output output = cmd_ctx->lsm.u.snapshot_output.output;
 
-               ret = cmd_snapshot_add_output(cmd_ctx->session, &output, &snapshot_id);
+               ret = cmd_snapshot_add_output(*target_session, &output, &snapshot_id);
                if (ret != LTTNG_OK) {
                        goto error;
                }
                reply.id = snapshot_id;
 
-               ret = setup_lttng_msg_no_cmd_header(cmd_ctx, &reply, sizeof(reply));
-               if (ret < 0) {
-                       goto setup_error;
-               }
+               setup_lttng_msg_no_cmd_header(cmd_ctx, &reply, sizeof(reply));
 
                /* Copy output list into message payload */
                ret = LTTNG_OK;
@@ -1989,67 +1997,64 @@ skip_domain:
        }
        case LTTCOMM_SESSIOND_COMMAND_SNAPSHOT_DEL_OUTPUT:
        {
-               lttng_snapshot_output output = cmd_ctx->lsm.u.snapshot_output.output;
-               ret = cmd_snapshot_del_output(cmd_ctx->session, &output);
+               const lttng_snapshot_output output = cmd_ctx->lsm.u.snapshot_output.output;
+               ret = cmd_snapshot_del_output(*target_session, &output);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_SNAPSHOT_LIST_OUTPUT:
        {
                ssize_t nb_output;
-               struct lttng_snapshot_output *outputs = NULL;
+               struct lttng_snapshot_output *outputs = nullptr;
 
-               nb_output = cmd_snapshot_list_outputs(cmd_ctx->session, &outputs);
+               nb_output = cmd_snapshot_list_outputs(*target_session, &outputs);
                if (nb_output < 0) {
                        ret = -nb_output;
                        goto error;
                }
 
                LTTNG_ASSERT((nb_output > 0 && outputs) || nb_output == 0);
-               ret = setup_lttng_msg_no_cmd_header(
+               setup_lttng_msg_no_cmd_header(
                        cmd_ctx, outputs, nb_output * sizeof(struct lttng_snapshot_output));
                free(outputs);
 
-               if (ret < 0) {
-                       goto setup_error;
-               }
-
                ret = LTTNG_OK;
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_SNAPSHOT_RECORD:
        {
-               lttng_snapshot_output output = cmd_ctx->lsm.u.snapshot_record.output;
-               ret = cmd_snapshot_record(cmd_ctx->session, &output, 0); // RFC: set to zero since
-                                                                        // it's ignored by
-                                                                        // cmd_snapshot_record
+               const lttng_snapshot_output output = cmd_ctx->lsm.u.snapshot_record.output;
+               ret = cmd_snapshot_record(*target_session, &output, 0); // RFC: set to zero
+                                                                       // since it's ignored
+                                                                       // by
+                                                                       // cmd_snapshot_record
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_CREATE_SESSION_EXT:
        {
                struct lttng_dynamic_buffer payload;
-               struct lttng_session_descriptor *return_descriptor = NULL;
 
                lttng_dynamic_buffer_init(&payload);
-               ret = cmd_create_session(cmd_ctx, *sock, &return_descriptor);
-               if (ret != LTTNG_OK) {
-                       goto error;
-               }
 
-               ret = lttng_session_descriptor_serialize(return_descriptor, &payload);
-               if (ret) {
-                       ERR("Failed to serialize session descriptor in reply to \"create session\" command");
-                       lttng_session_descriptor_destroy(return_descriptor);
-                       ret = LTTNG_ERR_NOMEM;
-                       goto error;
-               }
-               ret = setup_lttng_msg_no_cmd_header(cmd_ctx, payload.data, payload.size);
+               const lttng::ctl::session_descriptor reply_session_descriptor = [cmd_ctx, sock]() {
+                       lttng_session_descriptor *raw_descriptor;
+                       const auto create_ret = cmd_create_session(cmd_ctx, *sock, &raw_descriptor);
+                       if (create_ret != LTTNG_OK) {
+                               LTTNG_THROW_CTL("Failed to create session", create_ret);
+                       }
+
+                       return lttng::ctl::session_descriptor(raw_descriptor);
+               }();
+
+               ret = lttng_session_descriptor_serialize(reply_session_descriptor.get(), &payload);
                if (ret) {
-                       lttng_session_descriptor_destroy(return_descriptor);
-                       ret = LTTNG_ERR_NOMEM;
-                       goto error;
+                       LTTNG_THROW_CTL(
+                               "Failed to serialize session descriptor in reply to \"create session\" command",
+                               LTTNG_ERR_NOMEM);
                }
+
+               setup_lttng_msg_no_cmd_header(cmd_ctx, payload.data, payload.size);
+
                lttng_dynamic_buffer_reset(&payload);
-               lttng_session_descriptor_destroy(return_descriptor);
                ret = LTTNG_OK;
                break;
        }
@@ -2060,24 +2065,22 @@ skip_domain:
        }
        case LTTCOMM_SESSIOND_COMMAND_SET_SESSION_SHM_PATH:
        {
-               ret = cmd_set_session_shm_path(cmd_ctx->session,
+               ret = cmd_set_session_shm_path(*target_session,
                                               cmd_ctx->lsm.u.set_shm_path.shm_path);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_REGENERATE_METADATA:
        {
-               ret = cmd_regenerate_metadata(cmd_ctx->session);
+               ret = cmd_regenerate_metadata(*target_session);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_REGENERATE_STATEDUMP:
        {
-               ret = cmd_regenerate_statedump(cmd_ctx->session);
+               ret = cmd_regenerate_statedump(*target_session);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_REGISTER_TRIGGER:
        {
-               struct lttng_trigger *payload_trigger;
-               struct lttng_trigger *return_trigger;
                size_t original_reply_payload_size;
                size_t reply_payload_size;
                const struct lttng_credentials cmd_creds = {
@@ -2085,36 +2088,26 @@ skip_domain:
                        .gid = LTTNG_OPTIONAL_INIT_VALUE(cmd_ctx->creds.gid),
                };
 
-               ret = setup_empty_lttng_msg(cmd_ctx);
-               if (ret) {
-                       ret = LTTNG_ERR_NOMEM;
-                       goto setup_error;
-               }
+               setup_empty_lttng_msg(cmd_ctx);
 
-               ret = receive_lttng_trigger(cmd_ctx, *sock, sock_error, &payload_trigger);
+               auto payload_trigger = receive_lttng_trigger(cmd_ctx, *sock, sock_error);
                if (ret != LTTNG_OK) {
                        goto error;
                }
 
                original_reply_payload_size = cmd_ctx->reply_payload.buffer.size;
 
-               ret = cmd_register_trigger(&cmd_creds,
-                                          payload_trigger,
-                                          cmd_ctx->lsm.u.trigger.is_trigger_anonymous,
-                                          the_notification_thread_handle,
-                                          &return_trigger);
-               if (ret != LTTNG_OK) {
-                       lttng_trigger_put(payload_trigger);
-                       goto error;
-               }
+               auto return_trigger =
+                       cmd_register_trigger(&cmd_creds,
+                                            payload_trigger.get(),
+                                            cmd_ctx->lsm.u.trigger.is_trigger_anonymous,
+                                            the_notification_thread_handle);
 
-               ret = lttng_trigger_serialize(return_trigger, &cmd_ctx->reply_payload);
-               lttng_trigger_put(payload_trigger);
-               lttng_trigger_put(return_trigger);
+               ret = lttng_trigger_serialize(return_trigger.get(), &cmd_ctx->reply_payload);
                if (ret) {
-                       ERR("Failed to serialize trigger in reply to \"register trigger\" command");
-                       ret = LTTNG_ERR_NOMEM;
-                       goto error;
+                       LTTNG_THROW_CTL(
+                               "Failed to serialize trigger in reply to \"register trigger\" command",
+                               LTTNG_ERR_NOMEM);
                }
 
                reply_payload_size =
@@ -2127,36 +2120,31 @@ skip_domain:
        }
        case LTTCOMM_SESSIOND_COMMAND_UNREGISTER_TRIGGER:
        {
-               struct lttng_trigger *payload_trigger;
                const struct lttng_credentials cmd_creds = {
                        .uid = LTTNG_OPTIONAL_INIT_VALUE(cmd_ctx->creds.uid),
                        .gid = LTTNG_OPTIONAL_INIT_VALUE(cmd_ctx->creds.gid),
                };
 
-               ret = receive_lttng_trigger(cmd_ctx, *sock, sock_error, &payload_trigger);
-               if (ret != LTTNG_OK) {
-                       goto error;
-               }
+               auto payload_trigger = receive_lttng_trigger(cmd_ctx, *sock, sock_error);
 
                ret = cmd_unregister_trigger(
-                       &cmd_creds, payload_trigger, the_notification_thread_handle);
-               lttng_trigger_put(payload_trigger);
+                       &cmd_creds, payload_trigger.get(), the_notification_thread_handle);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_ROTATE_SESSION:
        {
                struct lttng_rotate_session_return rotate_return;
 
-               DBG("Client rotate session \"%s\"", cmd_ctx->session->name);
+               DBG("Client rotate session \"%s\"", (*target_session)->name);
 
                memset(&rotate_return, 0, sizeof(rotate_return));
-               if (cmd_ctx->session->kernel_session && !check_rotate_compatible()) {
+               if ((*target_session)->kernel_session && !check_rotate_compatible()) {
                        DBG("Kernel tracer version is not compatible with the rotation feature");
                        ret = LTTNG_ERR_ROTATION_WRONG_VERSION;
                        goto error;
                }
 
-               ret = cmd_rotate_session(cmd_ctx->session,
+               ret = cmd_rotate_session(*target_session,
                                         &rotate_return,
                                         false,
                                         LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED);
@@ -2165,11 +2153,7 @@ skip_domain:
                        goto error;
                }
 
-               ret = setup_lttng_msg_no_cmd_header(cmd_ctx, &rotate_return, sizeof(rotate_return));
-               if (ret < 0) {
-                       ret = -ret;
-                       goto error;
-               }
+               setup_lttng_msg_no_cmd_header(cmd_ctx, &rotate_return, sizeof(rotate_return));
 
                ret = LTTNG_OK;
                break;
@@ -2179,7 +2163,7 @@ skip_domain:
                struct lttng_rotation_get_info_return get_info_return;
 
                memset(&get_info_return, 0, sizeof(get_info_return));
-               ret = cmd_rotate_get_info(cmd_ctx->session,
+               ret = cmd_rotate_get_info(*target_session,
                                          &get_info_return,
                                          cmd_ctx->lsm.u.get_rotation_info.rotation_id);
                if (ret < 0) {
@@ -2187,12 +2171,7 @@ skip_domain:
                        goto error;
                }
 
-               ret = setup_lttng_msg_no_cmd_header(
-                       cmd_ctx, &get_info_return, sizeof(get_info_return));
-               if (ret < 0) {
-                       ret = -ret;
-                       goto error;
-               }
+               setup_lttng_msg_no_cmd_header(cmd_ctx, &get_info_return, sizeof(get_info_return));
 
                ret = LTTNG_OK;
                break;
@@ -2203,7 +2182,7 @@ skip_domain:
                enum lttng_rotation_schedule_type schedule_type;
                uint64_t value;
 
-               if (cmd_ctx->session->kernel_session && !check_rotate_compatible()) {
+               if ((*target_session)->kernel_session && !check_rotate_compatible()) {
                        DBG("Kernel tracer version does not support session rotations");
                        ret = LTTNG_ERR_ROTATION_WRONG_VERSION;
                        goto error;
@@ -2214,11 +2193,8 @@ skip_domain:
                                        cmd_ctx->lsm.u.rotation_set_schedule.type;
                value = cmd_ctx->lsm.u.rotation_set_schedule.value;
 
-               ret = cmd_rotation_set_schedule(cmd_ctx->session,
-                                               set_schedule,
-                                               schedule_type,
-                                               value,
-                                               the_notification_thread_handle);
+               ret = cmd_rotation_set_schedule(
+                       *target_session, set_schedule, schedule_type, value);
                if (ret != LTTNG_OK) {
                        goto error;
                }
@@ -2229,36 +2205,28 @@ skip_domain:
        {
                lttng_session_list_schedules_return schedules;
 
-               schedules.periodic.set = !!cmd_ctx->session->rotate_timer_period;
-               schedules.periodic.value = cmd_ctx->session->rotate_timer_period;
-               schedules.size.set = !!cmd_ctx->session->rotate_size;
-               schedules.size.value = cmd_ctx->session->rotate_size;
+               schedules.periodic.set = !!(*target_session)->rotate_timer_period;
+               schedules.periodic.value = (*target_session)->rotate_timer_period;
+               schedules.size.set = !!(*target_session)->rotate_size;
+               schedules.size.value = (*target_session)->rotate_size;
 
-               ret = setup_lttng_msg_no_cmd_header(cmd_ctx, &schedules, sizeof(schedules));
-               if (ret < 0) {
-                       ret = -ret;
-                       goto error;
-               }
+               setup_lttng_msg_no_cmd_header(cmd_ctx, &schedules, sizeof(schedules));
 
                ret = LTTNG_OK;
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_CLEAR_SESSION:
        {
-               ret = cmd_clear_session(cmd_ctx->session, sock);
+               ret = cmd_clear_session(*target_session, sock);
                break;
        }
        case LTTCOMM_SESSIOND_COMMAND_LIST_TRIGGERS:
        {
-               struct lttng_triggers *return_triggers = NULL;
+               struct lttng_triggers *return_triggers = nullptr;
                size_t original_payload_size;
                size_t payload_size;
 
-               ret = setup_empty_lttng_msg(cmd_ctx);
-               if (ret) {
-                       ret = LTTNG_ERR_NOMEM;
-                       goto setup_error;
-               }
+               setup_empty_lttng_msg(cmd_ctx);
 
                original_payload_size = cmd_ctx->reply_payload.buffer.size;
 
@@ -2290,15 +2258,11 @@ skip_domain:
                        .uid = LTTNG_OPTIONAL_INIT_VALUE(cmd_ctx->creds.uid),
                        .gid = LTTNG_OPTIONAL_INIT_VALUE(cmd_ctx->creds.gid),
                };
-               struct lttng_error_query_results *results = NULL;
+               struct lttng_error_query_results *results = nullptr;
                size_t original_payload_size;
                size_t payload_size;
 
-               ret = setup_empty_lttng_msg(cmd_ctx);
-               if (ret) {
-                       ret = LTTNG_ERR_NOMEM;
-                       goto setup_error;
-               }
+               setup_empty_lttng_msg(cmd_ctx);
 
                original_payload_size = cmd_ctx->reply_payload.buffer.size;
 
@@ -2339,27 +2303,15 @@ skip_domain:
 error:
        if (cmd_ctx->reply_payload.buffer.size == 0) {
                DBG("Missing llm header, creating one.");
-               if (setup_lttng_msg_no_cmd_header(cmd_ctx, NULL, 0) < 0) {
-                       goto setup_error;
-               }
-       }
-       /* Set return code */
-       ((struct lttcomm_lttng_msg *) (cmd_ctx->reply_payload.buffer.data))->ret_code = ret;
-setup_error:
-       if (cmd_ctx->session) {
-               session_unlock(cmd_ctx->session);
-               session_put(cmd_ctx->session);
-               cmd_ctx->session = NULL;
-       }
-       if (need_tracing_session) {
-               session_unlock_list();
+               setup_lttng_msg_no_cmd_header(cmd_ctx, nullptr, 0);
        }
-init_setup_error:
+
+       command_ctx_set_status_code(*cmd_ctx, static_cast<lttng_error_code>(ret));
        LTTNG_ASSERT(!rcu_read_ongoing());
        return ret;
 }
 
-static int create_client_sock(void)
+static int create_client_sock()
 {
        int ret, client_sock;
 
@@ -2407,6 +2359,51 @@ static void thread_init_cleanup(void *data __attribute__((unused)))
        set_thread_status(false);
 }
 
+// Helper function to log the source_location if the exception is derived from lttng::runtime_error
+template <typename ExceptionType>
+typename std::enable_if<std::is_base_of<lttng::runtime_error, ExceptionType>::value,
+                       std::string>::type
+formatted_source_location(const ExceptionType& ex)
+{
+       return fmt::format("{}", ex.source_location);
+}
+
+template <typename ExceptionType>
+typename std::enable_if<!std::is_base_of<lttng::runtime_error, ExceptionType>::value,
+                       std::string>::type
+formatted_source_location(const ExceptionType&)
+{
+       return "";
+}
+
+template <class ExceptionType>
+static void log_nested_exceptions(const ExceptionType& ex, unsigned int level = 0)
+{
+       const auto location = formatted_source_location(ex);
+
+       if (level == 0) {
+               if (location.size()) {
+                       WARN_FMT("Client request failed: {}, location='{}'", ex.what(), location);
+               } else {
+                       WARN_FMT("Client request failed: {}", ex.what());
+               }
+       } else {
+               if (location.size()) {
+                       WARN_FMT("\t{}, location='{}'", ex.what(), location);
+               } else {
+                       WARN_FMT("\t{}", ex.what());
+               }
+       }
+
+       try {
+               std::rethrow_if_nested(ex);
+       } catch (const lttng::runtime_error& nested_ex) {
+               log_nested_exceptions(nested_ex, level + 1);
+       } catch (const std::exception& nested_ex) {
+               log_nested_exceptions(nested_ex, level + 1);
+       }
+}
+
 /*
  * This thread manage all clients request using the unix client socket for
  * communication.
@@ -2428,7 +2425,7 @@ static void *thread_manage_clients(void *data)
 
        is_root = (getuid() == 0);
 
-       pthread_cleanup_push(thread_init_cleanup, NULL);
+       pthread_cleanup_push(thread_init_cleanup, nullptr);
 
        rcu_register_thread();
 
@@ -2477,13 +2474,12 @@ static void *thread_manage_clients(void *data)
 
        health_code_update();
 
-       while (1) {
+       while (true) {
                const struct cmd_completion_handler *cmd_completion_handler;
 
                cmd_ctx.creds.uid = UINT32_MAX;
                cmd_ctx.creds.gid = UINT32_MAX;
                cmd_ctx.creds.pid = 0;
-               cmd_ctx.session = NULL;
                lttng_payload_clear(&cmd_ctx.reply_payload);
                cmd_ctx.lttng_msg_size = 0;
 
@@ -2585,24 +2581,27 @@ static void *thread_manage_clients(void *data)
                 * informations for the client. The command context struct contains
                 * everything this function may needs.
                 */
-               ret = process_client_msg(&cmd_ctx, &sock, &sock_error);
-               rcu_thread_offline();
-               if (ret < 0) {
-                       if (sock >= 0) {
-                               ret = close(sock);
-                               if (ret) {
-                                       PERROR("close");
-                               }
-                       }
-                       sock = -1;
-                       /*
-                        * TODO: Inform client somehow of the fatal error. At
-                        * this point, ret < 0 means that a zmalloc failed
-                        * (ENOMEM). Error detected but still accept
-                        * command, unless a socket error has been
-                        * detected.
-                        */
-                       continue;
+               try {
+                       ret = process_client_msg(&cmd_ctx, &sock, &sock_error);
+                       rcu_thread_offline();
+               } catch (const std::bad_alloc& ex) {
+                       log_nested_exceptions(ex);
+                       ret = LTTNG_ERR_NOMEM;
+               } catch (const lttng::ctl::error& ex) {
+                       log_nested_exceptions(ex);
+                       ret = ex.code();
+               } catch (const lttng::invalid_argument_error& ex) {
+                       log_nested_exceptions(ex);
+                       ret = LTTNG_ERR_INVALID;
+               } catch (const lttng::sessiond::exceptions::session_not_found_error& ex) {
+                       log_nested_exceptions(ex);
+                       ret = LTTNG_ERR_SESS_NOT_FOUND;
+               } catch (const lttng::runtime_error& ex) {
+                       log_nested_exceptions(ex);
+                       ret = LTTNG_ERR_UNK;
+               } catch (const std::exception& ex) {
+                       log_nested_exceptions(ex);
+                       ret = LTTNG_ERR_UNK;
                }
 
                if (ret < LTTNG_OK || ret >= LTTNG_ERR_NR) {
@@ -2615,6 +2614,16 @@ static void *thread_manage_clients(void *data)
                        ret = LTTNG_ERR_UNK;
                }
 
+               if (ret != LTTNG_OK) {
+                       /*
+                        * Reset the payload contents as the command may have left them in an
+                        * inconsistent state.
+                        */
+                       setup_empty_lttng_msg(&cmd_ctx);
+               }
+
+               command_ctx_set_status_code(cmd_ctx, static_cast<lttng_error_code>(ret));
+
                cmd_completion_handler = cmd_pop_completion_handler();
                if (cmd_completion_handler) {
                        enum lttng_error_code completion_code;
@@ -2687,7 +2696,7 @@ error_create_poll:
        DBG("Client thread dying");
        lttng_payload_reset(&cmd_ctx.reply_payload);
        rcu_unregister_thread();
-       return NULL;
+       return nullptr;
 }
 
 static bool shutdown_client_thread(void *thread_data)
@@ -2698,11 +2707,11 @@ static bool shutdown_client_thread(void *thread_data)
        return notify_thread_pipe(write_fd) == 1;
 }
 
-struct lttng_thread *launch_client_thread(void)
+struct lttng_thread *launch_client_thread()
 {
        bool thread_running;
        struct lttng_pipe *client_quit_pipe;
-       struct lttng_thread *thread = NULL;
+       struct lttng_thread *thread = nullptr;
        int client_sock_fd = -1;
 
        sem_init(&thread_state.ready, 0, 0);
@@ -2727,7 +2736,7 @@ struct lttng_thread *launch_client_thread(void)
        }
        /* The client thread now owns the client sock fd and the quit pipe. */
        client_sock_fd = -1;
-       client_quit_pipe = NULL;
+       client_quit_pipe = nullptr;
 
        /*
         * This thread is part of the threads that need to be fully
@@ -2746,5 +2755,5 @@ error:
        }
        lttng_thread_put(thread);
        cleanup_client_thread(client_quit_pipe);
-       return NULL;
+       return nullptr;
 }
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