Fix: many-events registration/unregistration speed

[lttng-ust.git] / liblttng-ust / tracepoint.c

diff --git a/liblttng-ust/tracepoint.c b/liblttng-ust/tracepoint.c
index db5886009de5f620f24880e884b1345618470a2d..14b8231f879fca9d3aa8e3bde5a6a661cbb6b4c2 100644 (file)
--- a/liblttng-ust/tracepoint.c
+++ b/liblttng-ust/tracepoint.c
@@ -93,6 +93,9 @@ static struct cds_hlist_head tracepoint_table[TRACEPOINT_TABLE_SIZE];
 static CDS_LIST_HEAD(old_probes);
 static int need_update;
 
+static CDS_LIST_HEAD(release_queue);
+static int release_queue_need_update;
+
 /*
  * Note about RCU :
  * It is used to to delay the free of multiple probes array until a quiescent
@@ -553,6 +556,16 @@ tracepoint_add_probe(const char *name, void (*probe)(void), void *data,
        return old;
 }
 
+static void tracepoint_release_queue_add_old_probes(void *old)
+{
+       release_queue_need_update = 1;
+       if (old) {
+               struct tp_probes *tp_probes = caa_container_of(old,
+                       struct tp_probes, probes[0]);
+               cds_list_add(&tp_probes->u.list, &release_queue);
+       }
+}
+
 /**
  * __tracepoint_probe_register -  Connect a probe to a tracepoint
  * @name: tracepoint name
@@ -584,6 +597,33 @@ end:
        return ret;
 }
 
+/*
+ * Caller needs to invoke __tracepoint_probe_release_queue() after
+ * calling __tracepoint_probe_register_queue_release() one or multiple
+ * times to ensure it does not leak memory.
+ */
+int __tracepoint_probe_register_queue_release(const char *name,
+               void (*probe)(void), void *data, const char *signature)
+{
+       void *old;
+       int ret = 0;
+
+       DBG("Registering probe to tracepoint %s. Queuing release.", name);
+
+       pthread_mutex_lock(&tracepoint_mutex);
+       old = tracepoint_add_probe(name, probe, data, signature);
+       if (IS_ERR(old)) {
+               ret = PTR_ERR(old);
+               goto end;
+       }
+
+       tracepoint_sync_callsites(name);
+       tracepoint_release_queue_add_old_probes(old);
+end:
+       pthread_mutex_unlock(&tracepoint_mutex);
+       return ret;
+}
+
 static void *tracepoint_remove_probe(const char *name, void (*probe)(void),
                void *data)
 {
@@ -628,6 +668,57 @@ end:
        return ret;
 }
 
+/*
+ * Caller needs to invoke __tracepoint_probe_release_queue() after
+ * calling __tracepoint_probe_unregister_queue_release() one or multiple
+ * times to ensure it does not leak memory.
+ */
+int __tracepoint_probe_unregister_queue_release(const char *name,
+               void (*probe)(void), void *data)
+{
+       void *old;
+       int ret = 0;
+
+       DBG("Un-registering probe from tracepoint %s. Queuing release.", name);
+
+       pthread_mutex_lock(&tracepoint_mutex);
+       old = tracepoint_remove_probe(name, probe, data);
+       if (IS_ERR(old)) {
+               ret = PTR_ERR(old);
+               goto end;
+       }
+       tracepoint_sync_callsites(name);
+       tracepoint_release_queue_add_old_probes(old);
+end:
+       pthread_mutex_unlock(&tracepoint_mutex);
+       return ret;
+}
+
+void __tracepoint_probe_prune_release_queue(void)
+{
+       CDS_LIST_HEAD(release_probes);
+       struct tp_probes *pos, *next;
+
+       DBG("Release queue of unregistered tracepoint probes.");
+
+       pthread_mutex_lock(&tracepoint_mutex);
+       if (!release_queue_need_update)
+               goto end;
+       if (!cds_list_empty(&release_queue))
+               cds_list_replace_init(&release_queue, &release_probes);
+       release_queue_need_update = 0;
+
+       /* Wait for grace period between all sync_callsites and free. */
+       synchronize_rcu();
+
+       cds_list_for_each_entry_safe(pos, next, &release_probes, u.list) {
+               cds_list_del(&pos->u.list);
+               free(pos);
+       }
+end:
+       pthread_mutex_unlock(&tracepoint_mutex);
+}
+
 static void tracepoint_add_old_probes(void *old)
 {
        need_update = 1;
@@ -708,9 +799,10 @@ void tracepoint_probe_update_all(void)
        need_update = 0;
 
        tracepoint_update_probes();
+       /* Wait for grace period between update_probes and free. */
+       synchronize_rcu();
        cds_list_for_each_entry_safe(pos, next, &release_probes, u.list) {
                cds_list_del(&pos->u.list);
-               synchronize_rcu();
                free(pos);
        }
 end: