Fix: ust-consumer: metadata thread not woken-up after version change

[lttng-tools.git] / src / common / consumer / consumer-metadata-cache.c

diff --git a/src/common/consumer/consumer-metadata-cache.c b/src/common/consumer/consumer-metadata-cache.c
index 987bf7c8577d8c683a6b7e4a751c8b77ff2108a5..f712fa7f65043aeff6d688b06f9b22867683c8cc 100644 (file)
--- a/src/common/consumer/consumer-metadata-cache.c
+++ b/src/common/consumer/consumer-metadata-cache.c
@@ -23,6 +23,11 @@
 
 #include "consumer-metadata-cache.h"
 
+enum metadata_cache_update_version_status {
+       METADATA_CACHE_UPDATE_STATUS_VERSION_UPDATED,
+       METADATA_CACHE_UPDATE_STATUS_VERSION_NOT_UPDATED,
+};
+
 extern struct lttng_consumer_global_data consumer_data;
 
 /*
@@ -74,60 +79,23 @@ void metadata_cache_reset(struct consumer_metadata_cache *cache)
  * Check if the metadata cache version changed.
  * If it did, reset the metadata cache.
  * The metadata cache lock MUST be held.
- *
- * Returns 0 on success, a negative value on error.
  */
-static
-int metadata_cache_check_version(struct consumer_metadata_cache *cache,
-               uint64_t version)
+static enum metadata_cache_update_version_status metadata_cache_update_version(
+               struct consumer_metadata_cache *cache, uint64_t version)
 {
-       int ret = 0;
+       enum metadata_cache_update_version_status status;
 
        if (cache->version == version) {
+               status = METADATA_CACHE_UPDATE_STATUS_VERSION_NOT_UPDATED;
                goto end;
        }
 
        DBG("Metadata cache version update to %" PRIu64, version);
-       metadata_cache_reset(cache);
        cache->version = version;
+       status = METADATA_CACHE_UPDATE_STATUS_VERSION_UPDATED;
 
 end:
-       return ret;
-}
-
-/*
- * Write a character on the metadata poll pipe to wake the metadata thread.
- * Returns 0 on success, -1 on error.
- */
-int consumer_metadata_wakeup_pipe(const struct lttng_consumer_channel *channel)
-{
-       int ret = 0;
-       const char dummy = 'c';
-
-       if (channel->monitor && channel->metadata_stream) {
-               ssize_t write_ret;
-
-               write_ret = lttng_write(channel->metadata_stream->ust_metadata_poll_pipe[1],
-                               &dummy, 1);
-               if (write_ret < 1) {
-                       if (errno == EWOULDBLOCK) {
-                               /*
-                                * This is fine, the metadata poll thread
-                                * is having a hard time keeping-up, but
-                                * it will eventually wake-up and consume
-                                * the available data.
-                                */
-                               ret = 0;
-                       } else {
-                               PERROR("Wake-up UST metadata pipe");
-                               ret = -1;
-                               goto end;
-                       }
-               }
-       }
-
-end:
-       return ret;
+       return status;
 }
 
 /*
@@ -136,23 +104,31 @@ end:
  * contiguous metadata in cache to the ring buffer. The metadata cache
  * lock MUST be acquired to write in the cache.
  *
- * Return 0 on success, a negative value on error.
+ * See `enum consumer_metadata_cache_write_status` for the meaning of the
+ * various returned status codes.
  */
-int consumer_metadata_cache_write(struct lttng_consumer_channel *channel,
+enum consumer_metadata_cache_write_status
+consumer_metadata_cache_write(struct lttng_consumer_channel *channel,
                unsigned int offset, unsigned int len, uint64_t version,
                const char *data)
 {
        int ret = 0;
        struct consumer_metadata_cache *cache;
+       enum consumer_metadata_cache_write_status status;
+       bool cache_is_invalidated = false;
+       uint64_t original_max_offset;
 
        assert(channel);
        assert(channel->metadata_cache);
 
        cache = channel->metadata_cache;
+       ASSERT_LOCKED(cache->lock);
+       original_max_offset = cache->max_offset;
 
-       ret = metadata_cache_check_version(cache, version);
-       if (ret < 0) {
-               goto end;
+       if (metadata_cache_update_version(cache, version) ==
+                       METADATA_CACHE_UPDATE_STATUS_VERSION_UPDATED) {
+               metadata_cache_reset(cache);
+               cache_is_invalidated = true;
        }
 
        DBG("Writing %u bytes from offset %u in metadata cache", len, offset);
@@ -162,18 +138,25 @@ int consumer_metadata_cache_write(struct lttng_consumer_channel *channel,
                                len - cache->cache_alloc_size + offset);
                if (ret < 0) {
                        ERR("Extending metadata cache");
+                       status = CONSUMER_METADATA_CACHE_WRITE_STATUS_ERROR;
                        goto end;
                }
        }
 
        memcpy(cache->data + offset, data, len);
-       if (offset + len > cache->max_offset) {
-               cache->max_offset = offset + len;
-               ret = consumer_metadata_wakeup_pipe(channel);
+       cache->max_offset = max(cache->max_offset, offset + len);
+
+       if (cache_is_invalidated) {
+               status = CONSUMER_METADATA_CACHE_WRITE_STATUS_INVALIDATED;
+       } else if (cache->max_offset > original_max_offset) {
+               status = CONSUMER_METADATA_CACHE_WRITE_STATUS_APPENDED_CONTENT;
+       } else {
+               status = CONSUMER_METADATA_CACHE_WRITE_STATUS_NO_CHANGE;
+               assert(cache->max_offset == original_max_offset);
        }
 
 end:
-       return ret;
+       return status;
 }
 
 /*