lttng-abi: Document ioctl numbers reserved by lttng-abi-old.h

[lttng-modules.git] / lttng-context-vppid.c

diff --git a/lttng-context-vppid.c b/lttng-context-vppid.c
index 2fe2ffd1c1a0d02606f77f6232db27bf12797efe..66d638244c4cba12d4b8b411cb84b3632bda8cea 100644 (file)
--- a/lttng-context-vppid.c
+++ b/lttng-context-vppid.c
@@ -1,20 +1,20 @@
-/*
- * (C) Copyright       2009-2011 -
- *             Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+/* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
+ *
+ * lttng-context-vppid.c
  *
  * LTTng vPPID context.
  *
- * Dual LGPL v2.1/GPL v2 license.
+ * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  */
 
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/syscalls.h>
-#include "lttng-events.h"
-#include "wrapper/ringbuffer/frontend_types.h"
-#include "wrapper/vmalloc.h"
-#include "lttng-tracer.h"
+#include <lttng-events.h>
+#include <wrapper/ringbuffer/frontend_types.h>
+#include <wrapper/vmalloc.h>
+#include <lttng-tracer.h>
 
 static
 size_t vppid_get_size(size_t offset)
@@ -35,11 +35,21 @@ void vppid_record(struct lttng_ctx_field *field,
        pid_t vppid;
 
        /*
-        * nsproxy can be NULL when scheduled out of exit.
+        * current nsproxy can be NULL when scheduled out of exit. pid_vnr uses
+        * the current thread nsproxy to perform the lookup.
+        */
+
+       /*
+        * TODO: when we eventually add RCU subsystem instrumentation,
+        * taking the rcu read lock here will trigger RCU tracing
+        * recursively. We should modify the kernel synchronization so
+        * it synchronizes both for RCU and RCU sched, and rely on
+        * rcu_read_lock_sched_notrace.
         */
+
        rcu_read_lock();
        parent = rcu_dereference(current->real_parent);
-       if (!parent->nsproxy)
+       if (!current->nsproxy)
                vppid = 0;
        else
                vppid = task_tgid_vnr(parent);
@@ -48,6 +58,37 @@ void vppid_record(struct lttng_ctx_field *field,
        chan->ops->event_write(ctx, &vppid, sizeof(vppid));
 }
 
+static
+void vppid_get_value(struct lttng_ctx_field *field,
+               struct lttng_probe_ctx *lttng_probe_ctx,
+               union lttng_ctx_value *value)
+{
+       struct task_struct *parent;
+       pid_t vppid;
+
+       /*
+        * current nsproxy can be NULL when scheduled out of exit. pid_vnr uses
+        * the current thread nsproxy to perform the lookup.
+        */
+
+       /*
+        * TODO: when we eventually add RCU subsystem instrumentation,
+        * taking the rcu read lock here will trigger RCU tracing
+        * recursively. We should modify the kernel synchronization so
+        * it synchronizes both for RCU and RCU sched, and rely on
+        * rcu_read_lock_sched_notrace.
+        */
+
+       rcu_read_lock();
+       parent = rcu_dereference(current->real_parent);
+       if (!current->nsproxy)
+               vppid = 0;
+       else
+               vppid = task_tgid_vnr(parent);
+       rcu_read_unlock();
+       value->s64 = vppid;
+}
+
 int lttng_add_vppid_to_ctx(struct lttng_ctx **ctx)
 {
        struct lttng_ctx_field *field;
@@ -63,17 +104,15 @@ int lttng_add_vppid_to_ctx(struct lttng_ctx **ctx)
        field->event_field.type.atype = atype_integer;
        field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT;
        field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
-       field->event_field.type.u.basic.integer.signedness = is_signed_type(pid_t);
+       field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t);
        field->event_field.type.u.basic.integer.reverse_byte_order = 0;
        field->event_field.type.u.basic.integer.base = 10;
        field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
        field->get_size = vppid_get_size;
        field->record = vppid_record;
+       field->get_value = vppid_get_value;
+       lttng_context_update(*ctx);
        wrapper_vmalloc_sync_all();
        return 0;
 }
 EXPORT_SYMBOL_GPL(lttng_add_vppid_to_ctx);
-
-MODULE_LICENSE("GPL and additional rights");
-MODULE_AUTHOR("Mathieu Desnoyers");
-MODULE_DESCRIPTION("Linux Trace Toolkit vPPID Context");