glibc mq_notify memory leak report
Parthiban
parthiban@linumiz.com
Mon Jan 9 15:13:13 GMT 2023
Dear All,
I have the following code snippet and `mq_close`, `mq_unlink` is called in exit path.
But with valgrind, I have the summary about possibly lost.
How to gracefully remove the notification during exit path?
>From man mq_close,
If the calling process has attached a notification request (see (mq_notify(3)) to this
message queue via mqdes, then this request is removed
Valgrind summary:
```
==381555== HEAP SUMMARY:
==381555== in use at exit: 5,716 bytes in 13 blocks
==381555== total heap usage: 39,786 allocs, 39,773 frees, 267,728,707 bytes allocated
==381555==
==381555== Thread 1:
==381555== 304 bytes in 1 blocks are possibly lost in loss record 3 of 5
==381555== at 0x4846A73: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==381555== by 0x4011282: calloc (rtld-malloc.h:44)
==381555== by 0x4011282: allocate_dtv (dl-tls.c:375)
==381555== by 0x4011C91: _dl_allocate_tls (dl-tls.c:634)
==381555== by 0x4F244DF: allocate_stack (allocatestack.c:423)
==381555== by 0x4F244DF: pthread_create@@GLIBC_2.34 (pthread_create.c:650)
==381555== by 0x4F2E70E: init_mq_netlink (mq_notify.c:183)
==381555== by 0x4F28886: __pthread_once_slow (pthread_once.c:116)
==381555== by 0x4F2E802: __mq_notify (mq_notify.c:219)
==381555== by 0x4F2E802: mq_notify@@GLIBC_2.34 (mq_notify.c:203)
==381555== by 0x10C3D1: mq_notify_init (upstream.c:201)
==381555== by 0x10E306: mq_handler_init (upstream.c:1019)
==381555== by 0x10EDB6: upstream_init_async (upstream.c:1244)
==381555== by 0x10BFD6: main (main.c:83)
==381555==
==381555== LEAK SUMMARY:
==381555== definitely lost: 0 bytes in 0 blocks
==381555== indirectly lost: 0 bytes in 0 blocks
==381555== possibly lost: 304 bytes in 1 blocks
==381555== still reachable: 5,412 bytes in 12 blocks
==381555== suppressed: 0 bytes in 0 blocks
```
```
static int mq_notify_init(void)
{
int ret;
struct sigevent sev;
sev.sigev_notify = SIGEV_THREAD;
sev.sigev_notify_function = mq_handler;
sev.sigev_notify_attributes = NULL;
sev.sigev_value.sival_ptr = &mq;
ret = mq_notify(mq, &sev);
if (ret != 0)
error("MQ notify register failed: %s", strerror(errno));
return ret;
}
```
--
Thanks,
Parthiban N
https://www.linumiz.com
Berlin, Germany
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