92 lines
3.7 KiB
Diff
92 lines
3.7 KiB
Diff
commit 929a4764ac90382616b6a21f099192b2475da674
|
|
Author: Malte Skarupke <malteskarupke@fastmail.fm>
|
|
Date: Wed Dec 4 08:03:44 2024 -0500
|
|
|
|
nptl: Use a single loop in pthread_cond_wait instaed of a nested loop
|
|
|
|
The loop was a little more complicated than necessary. There was only one
|
|
break statement out of the inner loop, and the outer loop was nearly empty.
|
|
So just remove the outer loop, moving its code to the one break statement in
|
|
the inner loop. This allows us to replace all gotos with break statements.
|
|
|
|
Signed-off-by: Malte Skarupke <malteskarupke@fastmail.fm>
|
|
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
|
|
|
|
diff --git a/nptl/pthread_cond_wait.c b/nptl/pthread_cond_wait.c
|
|
index 9652dbafe08dfde1..4886056d136db138 100644
|
|
--- a/nptl/pthread_cond_wait.c
|
|
+++ b/nptl/pthread_cond_wait.c
|
|
@@ -383,17 +383,15 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
|
|
return err;
|
|
}
|
|
|
|
- /* Now wait until a signal is available in our group or it is closed.
|
|
- Acquire MO so that if we observe (signals == lowseq) after group
|
|
- switching in __condvar_quiesce_and_switch_g1, we synchronize with that
|
|
- store and will see the prior update of __g1_start done while switching
|
|
- groups too. */
|
|
- unsigned int signals = atomic_load_acquire (cond->__data.__g_signals + g);
|
|
-
|
|
- do
|
|
- {
|
|
+
|
|
while (1)
|
|
{
|
|
+ /* Now wait until a signal is available in our group or it is closed.
|
|
+ Acquire MO so that if we observe (signals == lowseq) after group
|
|
+ switching in __condvar_quiesce_and_switch_g1, we synchronize with that
|
|
+ store and will see the prior update of __g1_start done while switching
|
|
+ groups too. */
|
|
+ unsigned int signals = atomic_load_acquire (cond->__data.__g_signals + g);
|
|
uint64_t g1_start = __condvar_load_g1_start_relaxed (cond);
|
|
unsigned int lowseq = (g1_start & 1) == g ? signals : g1_start & ~1U;
|
|
|
|
@@ -402,7 +400,7 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
|
|
/* If the group is closed already,
|
|
then this waiter originally had enough extra signals to
|
|
consume, up until the time its group was closed. */
|
|
- goto done;
|
|
+ break;
|
|
}
|
|
|
|
/* If there is an available signal, don't block.
|
|
@@ -411,7 +409,16 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
|
|
G2, but in either case we're allowed to consume the available
|
|
signal and should not block anymore. */
|
|
if ((int)(signals - lowseq) >= 2)
|
|
- break;
|
|
+ {
|
|
+ /* Try to grab a signal. See above for MO. (if we do another loop
|
|
+ iteration we need to see the correct value of g1_start) */
|
|
+ if (atomic_compare_exchange_weak_acquire (
|
|
+ cond->__data.__g_signals + g,
|
|
+ &signals, signals - 2))
|
|
+ break;
|
|
+ else
|
|
+ continue;
|
|
+ }
|
|
|
|
// Now block.
|
|
struct _pthread_cleanup_buffer buffer;
|
|
@@ -432,19 +439,9 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
|
|
/* If we timed out, we effectively cancel waiting. */
|
|
__condvar_cancel_waiting (cond, seq, g, private);
|
|
result = err;
|
|
- goto done;
|
|
+ break;
|
|
}
|
|
-
|
|
- /* Reload signals. See above for MO. */
|
|
- signals = atomic_load_acquire (cond->__data.__g_signals + g);
|
|
}
|
|
- }
|
|
- /* Try to grab a signal. See above for MO. (if we do another loop
|
|
- iteration we need to see the correct value of g1_start) */
|
|
- while (!atomic_compare_exchange_weak_acquire (cond->__data.__g_signals + g,
|
|
- &signals, signals - 2));
|
|
-
|
|
- done:
|
|
|
|
/* Confirm that we have been woken. We do that before acquiring the mutex
|
|
to allow for execution of pthread_cond_destroy while having acquired the
|