[lttng-dev] [PATCH lttng-ust v2] Fix: allocate ts_end in ringbuffer shared memory

Gabriel-Andrew Pollo-Guilbert gabriel.pollo-guilbert at efficios.com
Fri May 10 11:26:32 EDT 2019

This patch allocates the memory used by the ts_end field added by commit
6c737d05. When allocating lots of subbuffer for a channel (512 or more),
zalloc_shm() will fail to allocate all the objects because the allocated memory
map didn't take account the newly added field.

lttng-tools version: b14f53d4 (2.12.0-pre)

Steps to reproduce the bug:

	1. lttng-sessiond -vvv --verbose-consumer
	2. start a traced application
	3. lttng create "test-sesssion"
	4. lttng enable-channel --userspace --num-subbuf 512 --subbuf-size 8k --overwrite channel
	5. lttng enable-event -u -a -c channel
	6. lttng start

After these steps, the following error message show should be thrown:

	Error: ask_channel_creation consumer command failed
	Error: Error creating UST channel "channel" on the consumer daemon

Signed-off-by: Gabriel-Andrew Pollo-Guilbert <gabriel.pollo-guilbert at efficios.com>
 libringbuffer/ring_buffer_backend.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/libringbuffer/ring_buffer_backend.c b/libringbuffer/ring_buffer_backend.c
index a0ef7446..431b8eae 100644
--- a/libringbuffer/ring_buffer_backend.c
+++ b/libringbuffer/ring_buffer_backend.c
@@ -341,6 +341,9 @@ int channel_backend_init(struct channel_backend *chanb,
 	shmsize += sizeof(struct commit_counters_hot) * num_subbuf;
 	shmsize += offset_align(shmsize, __alignof__(struct commit_counters_cold));
 	shmsize += sizeof(struct commit_counters_cold) * num_subbuf;
+	/* Sampled timestamp end */
+	shmsize += offset_align(shmsize, __alignof__(uint64_t));
+	shmsize += sizeof(uint64_t) * num_subbuf;
 	if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 		struct lttng_ust_lib_ring_buffer *buf;

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