Keep perf context FD open for other architectures

[lttng-ust.git] / liblttng-ust / lttng-context-perf-counters.c

diff --git a/liblttng-ust/lttng-context-perf-counters.c b/liblttng-ust/lttng-context-perf-counters.c
index 97ddf977d1ba17706ae337bb66d3c1241da13038..383d020ce42e02be05c4c89dbd578294091aa6c9 100644 (file)
--- a/liblttng-ust/lttng-context-perf-counters.c
+++ b/liblttng-ust/lttng-context-perf-counters.c
@@ -55,6 +55,7 @@ struct lttng_perf_counter_thread_field {
        struct perf_event_mmap_page *pc;
        struct cds_list_head thread_field_node; /* Per-field list of thread fields (node) */
        struct cds_list_head rcu_field_node;    /* RCU per-thread list of fields (node) */
+       int fd;                                 /* Perf FD */
 };
 
 struct lttng_perf_counter_thread {
@@ -90,6 +91,11 @@ uint64_t rdpmc(unsigned int counter)
        return low | ((uint64_t) high) << 32;
 }
 
+static bool arch_perf_use_read(void)
+{
+       return false;
+}
+
 #else /* defined(__x86_64__) || defined(__i386__) */
 
 #error "Perf event counters are only supported on x86 so far."
@@ -131,26 +137,50 @@ int sys_perf_event_open(struct perf_event_attr *attr,
 }
 
 static
-struct perf_event_mmap_page *setup_perf(struct perf_event_attr *attr)
+int open_perf_fd(struct perf_event_attr *attr)
 {
-       void *perf_addr;
-       int fd, ret;
+       int fd;
 
        fd = sys_perf_event_open(attr, 0, -1, -1, 0);
        if (fd < 0)
-               return NULL;
+               return -1;
+
+       return fd;
+}
+
+static
+struct perf_event_mmap_page *setup_perf(
+               struct lttng_perf_counter_thread_field *thread_field)
+{
+       void *perf_addr;
 
        perf_addr = mmap(NULL, sizeof(struct perf_event_mmap_page),
-                       PROT_READ, MAP_SHARED, fd, 0);
+                       PROT_READ, MAP_SHARED, thread_field->fd, 0);
        if (perf_addr == MAP_FAILED)
-               return NULL;
-       ret = close(fd);
-       if (ret) {
-               perror("Error closing LTTng-UST perf memory mapping FD");
+               perf_addr = NULL;
+
+       if (!arch_perf_use_read()) {
+               close_perf_fd(thread_field->fd);
+               thread_field->fd = -1;
        }
+
+end:
        return perf_addr;
 }
 
+static
+void close_perf_fd(int fd)
+{
+       int ret;
+
+       if (fd < 0)
+               return;
+
+       ret = close(fd);
+       if (ret)
+               perror("Error closing LTTng-UST perf memory mapping FD");
+}
+
 static
 void unmap_perf_page(struct perf_event_mmap_page *pc)
 {
@@ -221,8 +251,13 @@ struct lttng_perf_counter_thread_field *
        if (!thread_field)
                abort();
        thread_field->field = perf_field;
-       thread_field->pc = setup_perf(&perf_field->attr);
-       /* Note: thread_field->pc can be NULL if setup_perf() fails. */
+       thread_field->fd = open_perf_fd(&perf_field->attr);
+       if (thread_field->fd >= 0)
+               thread_field->pc = setup_perf(thread_field);
+       /*
+        * Note: thread_field->pc can be NULL if setup_perf() fails.
+        * Also, thread_field->fd can be -1 if open_perf_fd() fails.
+        */
        ust_lock_nocheck();
        cds_list_add_rcu(&thread_field->rcu_field_node,
                        &perf_thread->rcu_field_list);
@@ -293,6 +328,7 @@ static
 void lttng_destroy_perf_thread_field(
                struct lttng_perf_counter_thread_field *thread_field)
 {
+       close_perf_fd(thread_field->fd);
        unmap_perf_page(thread_field->pc);
        cds_list_del_rcu(&thread_field->rcu_field_node);
        cds_list_del(&thread_field->thread_field_node);
@@ -341,7 +377,6 @@ int lttng_add_perf_counter_to_ctx(uint32_t type,
 {
        struct lttng_ctx_field *field;
        struct lttng_perf_counter_field *perf_field;
-       struct perf_event_mmap_page *tmp_pc;
        char *name_alloc;
        int ret;
 
@@ -389,12 +424,12 @@ int lttng_add_perf_counter_to_ctx(uint32_t type,
        field->u.perf_counter = perf_field;
 
        /* Ensure that this perf counter can be used in this process. */
-       tmp_pc = setup_perf(&perf_field->attr);
-       if (!tmp_pc) {
+       ret = open_perf_fd(&perf_field->attr);
+       if (ret < 0) {
                ret = -ENODEV;
                goto setup_error;
        }
-       unmap_perf_page(tmp_pc);
+       close_perf_fd(ret);
 
        /*
         * Contexts can only be added before tracing is started, so we