Fix: coherent state not changed atomically with metadata written

[lttng-modules.git] / src / lttng-events.c

diff --git a/src/lttng-events.c b/src/lttng-events.c
index 3b9b907beb85196b36301cbb6df6456ab195b23b..2b72621cf2d6fccacaed54e3c8dde1159500ddb5 100644 (file)
--- a/src/lttng-events.c
+++ b/src/lttng-events.c
@@ -1673,7 +1673,7 @@ int lttng_metadata_output_channel(struct lttng_metadata_stream *stream,
                        reserve_len);
        stream->transport->ops.event_commit(&ctx);
        stream->metadata_in += reserve_len;
-       if (reserve_len < len || stream->metadata_cache->producing != 0)
+       if (reserve_len < len)
                stream->coherent = false;
        else
                stream->coherent = true;
@@ -1689,18 +1689,21 @@ end:
 static
 void lttng_metadata_begin(struct lttng_session *session)
 {
-       mutex_lock(&session->metadata_cache->lock);
-       session->metadata_cache->producing++;
-       mutex_unlock(&session->metadata_cache->lock);
+       if (atomic_inc_return(&session->metadata_cache->producing) == 1)
+               mutex_lock(&session->metadata_cache->lock);
 }
 
 static
 void lttng_metadata_end(struct lttng_session *session)
 {
-       mutex_lock(&session->metadata_cache->lock);
-       WARN_ON_ONCE(!session->metadata_cache->producing);
-       session->metadata_cache->producing--;
-       mutex_unlock(&session->metadata_cache->lock);
+       WARN_ON_ONCE(!atomic_read(&session->metadata_cache->producing));
+       if (atomic_dec_return(&session->metadata_cache->producing) == 0) {
+               struct lttng_metadata_stream *stream;
+
+               mutex_unlock(&session->metadata_cache->lock);
+               list_for_each_entry(stream, &session->metadata_cache->metadata_stream, list)
+                       wake_up_interruptible(&stream->read_wait);
+       }
 }
 
 /*
@@ -1717,7 +1720,6 @@ int lttng_metadata_printf(struct lttng_session *session,
        char *str;
        size_t len;
        va_list ap;
-       struct lttng_metadata_stream *stream;
 
        WARN_ON_ONCE(!READ_ONCE(session->active));
 
@@ -1728,8 +1730,7 @@ int lttng_metadata_printf(struct lttng_session *session,
                return -ENOMEM;
 
        len = strlen(str);
-       mutex_lock(&session->metadata_cache->lock);
-       session->metadata_cache->producing++;
+       WARN_ON_ONCE(!atomic_read(&session->metadata_cache->producing));
        if (session->metadata_cache->metadata_written + len >
                        session->metadata_cache->cache_alloc) {
                char *tmp_cache_realloc;
@@ -1755,18 +1756,11 @@ int lttng_metadata_printf(struct lttng_session *session,
                        session->metadata_cache->metadata_written,
                        str, len);
        session->metadata_cache->metadata_written += len;
-       session->metadata_cache->producing--;
-       mutex_unlock(&session->metadata_cache->lock);
        kfree(str);
 
-       list_for_each_entry(stream, &session->metadata_cache->metadata_stream, list)
-               wake_up_interruptible(&stream->read_wait);
-
        return 0;
 
 err:
-       session->metadata_cache->producing--;
-       mutex_unlock(&session->metadata_cache->lock);
        kfree(str);
        return -ENOMEM;
 }