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

[Sebastien Boisvert]

On 2019-05-10 11:26 a.m., Gabriel-Andrew Pollo-Guilbert wrote:

Hello Gabriel-Andrew,

> 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

I need to killall existing lttng-sessiond daemon, right ?

> 	2. start a traced application

I used lttng-ust/doc/examples/demo/.

> 	3. lttng create "test-sesssion"
                                ^^^
There are too many s in session.


> 	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

When I build lttng-tools b14f53d4

I get this error:

make[3]: Entering directory '/home/sboisvert/open-source/lttng.org/Source/lttng-tools/src/common/ust-consumer'
  CC       ust-consumer.lo
ust-consumer.c: In function 'lttng_ustconsumer_recv_cmd':
ust-consumer.c:1459:7: error: 'struct ustctl_consumer_channel_attr' has no member named 'blocking_timeout'
   attr.blocking_timeout= msg.u.ask_channel.blocking_timeout;
       ^
ust-consumer.c: In function 'lttng_ustconsumer_sample_snapshot_positions':
ust-consumer.c:2225:9: warning: implicit declaration of function 'ustctl_snapshot_sample_positions'; did you mean 'ustctl_snapshot_get_produced'? [-Wimplicit-function-declaration]
  return ustctl_snapshot_sample_positions(stream->ustream);
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
         ustctl_snapshot_get_produced
Makefile:548: recipe for target 'ust-consumer.lo' failed


There seems to be 2 declarations of struct ustctl_consumer_channel_attr.

In file lttng-tools/src/bin/lttng-sessiond/lttng-ust-ctl.h,
struct ustctl_consumer_channel_attr has the attribute blocking_timeout.

In file lttng-ust/include/lttng/ust-ctl.h, struct ustctl_consumer_channel_attr
does not have the attribute.


They are exactly the same, except the missing blocking_timeout attribute.


[sboisvert at GT480:Source]$ grep -A 10 "struct ustctl_consumer_channel_attr {" lttng-ust/include/lttng/ust-ctl.h
struct ustctl_consumer_channel_attr {
	enum lttng_ust_chan_type type;
	uint64_t subbuf_size;			/* bytes */
	uint64_t num_subbuf;			/* power of 2 */
	int overwrite;				/* 1: overwrite, 0: discard */
	unsigned int switch_timer_interval;	/* usec */
	unsigned int read_timer_interval;	/* usec */
	enum lttng_ust_output output;		/* splice, mmap */
	uint32_t chan_id;			/* channel ID */
	unsigned char uuid[LTTNG_UST_UUID_LEN]; /* Trace session unique ID */
} LTTNG_PACKED;

[sboisvert at GT480:Source]$ grep -A 11 "struct ustctl_consumer_channel_attr {" lttng-tools/src/bin/lttng-sessiond/lttng-ust-ctl.h
struct ustctl_consumer_channel_attr {
	enum lttng_ust_chan_type type;
	uint64_t subbuf_size;			/* bytes */
	uint64_t num_subbuf;			/* power of 2 */
	int overwrite;				/* 1: overwrite, 0: discard */
	unsigned int switch_timer_interval;	/* usec */
	unsigned int read_timer_interval;	/* usec */
	enum lttng_ust_output output;		/* splice, mmap */
	uint32_t chan_id;			/* channel ID */
	unsigned char uuid[LTTNG_UST_UUID_LEN]; /* Trace session unique ID */
	int64_t blocking_timeout;			/* Blocking timeout (usec) */
} LTTNG_PACKED;

[sboisvert at GT480:Source]$ diff -u <(grep -A 11 "struct ustctl_consumer_channel_attr {" lttng-tools/src/bin/lttng-sessiond/lttng-ust-ctl.h) <(grep -A 10 "struct ustctl_consumer_channel_attr {" lttng-ust/include/lttng/ust-ctl.h)
--- /dev/fd/63	2019-05-10 12:32:23.562246820 -0400
+++ /dev/fd/62	2019-05-10 12:32:23.562246820 -0400
@@ -8,5 +8,4 @@
 	enum lttng_ust_output output;		/* splice, mmap */
 	uint32_t chan_id;			/* channel ID */
 	unsigned char uuid[LTTNG_UST_UUID_LEN]; /* Trace session unique ID */
-	int64_t blocking_timeout;			/* Blocking timeout (usec) */
 } LTTNG_PACKED;

 
My configure commands (followed by "make install"):

[sboisvert at GT480:userspace-rcu]$ ./configure --prefix=/home/sboisvert/open-source/lttng.org/Build/userspace-rcu/v0.11.0

[sboisvert at GT480:lttng-ust]$ ./configure --prefix=/home/sboisvert/open-source/lttng.org/Build/lttng-ust/v2.9.4 LDFLAGS=-L/home/sboisvert/open-source/lttng.org/Build/userspace-rcu/v0.11.0/lib

[sboisvert at GT480:lttng-tools]$ ./configure --prefix=/home/sboisvert/open-source/lttng.org/Build/lttng-tools/b14f53d4 LDFLAGS=-L/home/sboisvert/open-source/lttng.org/Build/lttng-ust/v2.9.4/lib CPPFLAGS=-I/home/sboisvert/open-source/lttng.org/Build/lttng-ust/v2.9.4/include


Thanks     

> 
> 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;
>