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Fix fat_mutex owner corruption and other problems in fat_mutex_unlock.

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Fixes <https://debbugs.gnu.org/22152>.
Reported by Iwan Aucamp <aucampia@gmail.com>.

* libguile/threads.c (fat_mutex_unlock): Avoid repeatedly decrementing
  m->level and changing the owner of the mutex when 'block_self' returns
  EINTR.  Unblock asyncs before calling scm_syserror.  Refactor the code
  to clarify the EINTR loop, and to make it more apparent that the async
  blocks and unblocks are balanced.
This commit is contained in:
Mark H Weaver 2015-12-18 02:29:48 -05:00
parent 4b60562820
commit 1e86dc32a4
1 changed files with 36 additions and 51 deletions
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63
libguile/threads.c
View file

@ -1607,13 +1607,6 @@ fat_mutex_unlock (SCM mutex, SCM cond,
} }
} }
if (! (SCM_UNBNDP (cond)))
{
c = SCM_CONDVAR_DATA (cond);
while (1)
{
int brk = 0;
if (m->level > 0) if (m->level > 0)
m->level--; m->level--;
if (m->level == 0) if (m->level == 0)
@ -1623,54 +1616,46 @@ fat_mutex_unlock (SCM mutex, SCM cond,
m->owner = unblock_from_queue (m->waiting); m->owner = unblock_from_queue (m->waiting);
} }
if (! (SCM_UNBNDP (cond)))
{
c = SCM_CONDVAR_DATA (cond);
t->block_asyncs++; t->block_asyncs++;
do
{
err = block_self (c->waiting, cond, &m->lock, waittime); err = block_self (c->waiting, cond, &m->lock, waittime);
scm_i_pthread_mutex_unlock (&m->lock); scm_i_pthread_mutex_unlock (&m->lock);
if (err == 0) if (err == EINTR)
{ {
ret = 1;
brk = 1;
}
else if (err == ETIMEDOUT)
{
ret = 0;
brk = 1;
}
else if (err != EINTR)
{
errno = err;
scm_syserror (NULL);
}
if (brk)
{
if (relock)
scm_lock_mutex_timed (mutex, SCM_UNDEFINED, owner);
t->block_asyncs--;
break;
}
t->block_asyncs--; t->block_asyncs--;
scm_async_click (); scm_async_click ();
scm_remember_upto_here_2 (cond, mutex); scm_remember_upto_here_2 (cond, mutex);
scm_i_scm_pthread_mutex_lock (&m->lock); scm_i_scm_pthread_mutex_lock (&m->lock);
t->block_asyncs++;
} }
} }
while (err == EINTR);
if (err == 0)
ret = 1;
else if (err == ETIMEDOUT)
ret = 0;
else
{
t->block_asyncs--;
errno = err;
scm_syserror (NULL);
}
if (relock)
scm_lock_mutex_timed (mutex, SCM_UNDEFINED, owner);
t->block_asyncs--;
}
else else
{ {
if (m->level > 0)
m->level--;
if (m->level == 0)
{
/* Change the owner of MUTEX. */
t->mutexes = scm_delq_x (mutex, t->mutexes);
m->owner = unblock_from_queue (m->waiting);
}
scm_i_pthread_mutex_unlock (&m->lock); scm_i_pthread_mutex_unlock (&m->lock);
ret = 1; ret = 1;
} }