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eina: fixtures on OSX semaphores 

So actually there is quite a big issue with semaphores
on OSX. We use (named) POSIX semaphores, but this was
a (my) mistake... I'll fix it later...
The real issue is that named semaphore are persistants:
when the program dies, it stays alive. This is pretty
bad with eina_debug_monitor because we create a semaphore
we never release, due to a wild thread...

This leak of semaphores went unnoticed before commit
4a40ff95de because the
name of the semaphore was unique per process, and
overriden when another process was launched. This
was very bad, but saved us from overflowing the
semaphore pool. It is now overflowed pretty fast when
building a lot EFL, because of Eolian that runs A LOT!

So that's one problem that still needs to be fixed,
by using OSX' own semaphores (see T4423).
Another big issue, which is now fixed is that the
buffer in which we generated the semaphore ID was
too small, and therefore we were reduced to one shared
semaphore for a whole process... This buffer has been
now set to 31 characters, which seems to be the maximum
length of a semaphore ID.

So now things are better, but still with a deadly issue.
This commit is contained in:
Jean Guyomarc'h 2016-08-23 16:59:10 +02:00 committed by Jean Guyomarc'h
parent 469cf26873
commit 180b24f2a0
1 changed files with 8 additions and 21 deletions
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29
src/lib/eina/eina_inline_lock_posix.x
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@ -96,22 +96,13 @@ typedef Eina_Lock Eina_Spinlock;
#if defined(EINA_HAVE_OSX_SEMAPHORE)
/* OSX supports only named semaphores.
* So, we need to be able to generate a unique string identifier for each
* semaphore we want to create.
* It seems reasonable to use a counter, which is incremented each time a
* semaphore is created. However, it needs to be atomic...
* It would be easier if we were using C11 with stdatomic, but I guess it
* will just be fine without.
* That's why there are two static variables below the struct */
* semaphore we want to create. */
struct _Eina_Semaphore
{
sem_t *sema;
char name[16];
char name[32];
};
typedef struct _Eina_Semaphore Eina_Semaphore;
static unsigned int _sem_ctr = 0;
static Eina_Spinlock _sem_ctr_lock = 0; // 0: not locked
#else
typedef sem_t Eina_Semaphore;
#endif
@ -848,14 +839,9 @@ eina_semaphore_new(Eina_Semaphore *sem, int count_init)
#if defined(EINA_HAVE_OSX_SEMAPHORE)
/* Atomic increment to generate the unique identifier */
eina_spinlock_take(&_sem_ctr_lock);
++_sem_ctr;
eina_spinlock_release(&_sem_ctr_lock);
snprintf(sem->name, sizeof(sem->name), "/eina_sem_%x-%x_%x_%x_%x_%x",
(unsigned int)getpid(), _sem_ctr,
(unsigned int)rand(), (unsigned int)rand(),
(unsigned int)rand(), (unsigned int)rand());
snprintf(sem->name, sizeof(sem->name), "/eina%x%x%x",
(unsigned int)getpid(), (unsigned int)rand(), (unsigned int)rand());
sem->name[sizeof(sem->name) - 1] = '\0';
sem_unlink(sem->name);
sem->sema = sem_open(sem->name, O_CREAT | O_EXCL, 0600, count_init);
return (sem->sema == SEM_FAILED) ? EINA_FALSE : EINA_TRUE;
@ -871,8 +857,9 @@ eina_semaphore_free(Eina_Semaphore *sem)
return EINA_FALSE;
#if defined(EINA_HAVE_OSX_SEMAPHORE)
return ((sem_close(sem->sema) == 0) &&
(sem_unlink(sem->name)) == 0) ? EINA_TRUE : EINA_FALSE;
const int closed = sem_close(sem->sema);
const int unlinked = sem_unlink(sem->name);
return ((closed == 0) && (unlinked == 0)) ? EINA_TRUE : EINA_FALSE;
#else
return (sem_destroy(sem) == 0) ? EINA_TRUE : EINA_FALSE;
#endif