This command allows the consumer to ask for the metadata cache to be dumped entirely another time. This is used by the session rotation feature to get a new copy of what was in the metadata cache without regenerating it and re-sampling the offset from epoch.
Signed-off-by: Julien Desfossez <[email protected]> --- lib/ringbuffer/vfs.h | 5 +++++ lttng-abi.c | 44 ++++++++++++++++++++++++++++++++++++++++++++ lttng-events.c | 2 -- 3 files changed, 49 insertions(+), 2 deletions(-) diff --git a/lib/ringbuffer/vfs.h b/lib/ringbuffer/vfs.h index b2e5b1c..e2bc401 100644 --- a/lib/ringbuffer/vfs.h +++ b/lib/ringbuffer/vfs.h @@ -123,6 +123,11 @@ ssize_t vfs_lib_ring_buffer_splice_read(struct file *in, loff_t *ppos, #define RING_BUFFER_SNAPSHOT_SAMPLE_POSITIONS _IO(0xF6, 0x0E) /* Flush the current sub-buffer, even if empty. */ #define RING_BUFFER_FLUSH_EMPTY _IO(0xF6, 0x0F) +/* + * Reset the position of what has been consumed from the metadata cache to 0 + * so it can be read again. + */ +#define RING_BUFFER_METADATA_CACHE_DUMP _IO(0xF6, 0x10) #ifdef CONFIG_COMPAT /* Get a snapshot of the current ring buffer producer and consumer positions */ diff --git a/lttng-abi.c b/lttng-abi.c index 77e5e98..d202b72 100644 --- a/lttng-abi.c +++ b/lttng-abi.c @@ -654,6 +654,38 @@ void lttng_metadata_ring_buffer_ioctl_put_next_subbuf(struct file *filp, stream->metadata_out = stream->metadata_in; } +/* + * Reset the counter of how much metadata has been consumed to 0. That way, + * the consumer receives the content of the metadata cache unchanged. This is + * different from the metadata_regenerate where the offset from epoch is + * resampled, here we want the exact same content as the last time the metadata + * was generated. This command is only possible if all the metadata written + * in the cache has been output to the metadata stream to avoid corrupting the + * metadata file. + * + * Return 0 on success, a negative value on error. + */ +static +int lttng_metadata_cache_dump(struct lttng_metadata_stream *stream) +{ + int ret; + struct lttng_metadata_cache *cache = stream->metadata_cache; + + mutex_lock(&cache->lock); + if (stream->metadata_out != cache->metadata_written) { + ret = -EBUSY; + goto end; + } + stream->metadata_out = 0; + stream->metadata_in = 0; + wake_up_interruptible(&stream->read_wait); + ret = 0; + +end: + mutex_unlock(&cache->lock); + return ret; +} + static long lttng_metadata_ring_buffer_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) @@ -706,6 +738,12 @@ long lttng_metadata_ring_buffer_ioctl(struct file *filp, return put_u64(stream->version, arg); } + case RING_BUFFER_METADATA_CACHE_DUMP: + { + struct lttng_metadata_stream *stream = filp->private_data; + + return lttng_metadata_cache_dump(stream); + } default: break; } @@ -783,6 +821,12 @@ long lttng_metadata_ring_buffer_compat_ioctl(struct file *filp, return put_u64(stream->version, arg); } + case RING_BUFFER_METADATA_CACHE_DUMP: + { + struct lttng_metadata_stream *stream = filp->private_data; + + return lttng_metadata_cache_dump(stream); + } default: break; } diff --git a/lttng-events.c b/lttng-events.c index 21c4113..8719173 100644 --- a/lttng-events.c +++ b/lttng-events.c @@ -342,8 +342,6 @@ end: return ret; } - - int lttng_channel_enable(struct lttng_channel *channel) { int ret = 0; -- 2.7.4 _______________________________________________ lttng-dev mailing list [email protected] https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
