@@ -57,7 +57,7 @@ ___pthread_cond_broadcast (pthread_cond_t *cond)
{
/* Add as many signals as the remaining size of the group. */
atomic_fetch_add_relaxed (cond->__data.__g_signals + g1,
- cond->__data.__g_size[g1] << 1);
+ cond->__data.__g_size[g1]);
cond->__data.__g_size[g1] = 0;
/* We need to wake G1 waiters before we switch G1 below. */
@@ -73,7 +73,7 @@ ___pthread_cond_broadcast (pthread_cond_t *cond)
{
/* Step (3): Send signals to all waiters in the old G2 / new G1. */
atomic_fetch_add_relaxed (cond->__data.__g_signals + g1,
- cond->__data.__g_size[g1] << 1);
+ cond->__data.__g_size[g1]);
cond->__data.__g_size[g1] = 0;
/* TODO Only set it if there are indeed futex waiters. */
do_futex_wake = true;
@@ -208,9 +208,9 @@ __condvar_switch_g1 (pthread_cond_t *cond, uint64_t wseq,
behavior.
Note that this works correctly for a zero-initialized condvar too. */
unsigned int old_orig_size = __condvar_get_orig_size (cond);
- uint64_t old_g1_start = __condvar_load_g1_start_relaxed (cond) >> 1;
- if (((unsigned) (wseq - old_g1_start - old_orig_size)
- + cond->__data.__g_size[g1 ^ 1]) == 0)
+ uint64_t old_g1_start = __condvar_load_g1_start_relaxed (cond);
+ uint64_t new_g1_start = old_g1_start + old_orig_size;
+ if (((unsigned) (wseq - new_g1_start) + cond->__data.__g_size[g1 ^ 1]) == 0)
return false;
/* We have to consider the following kinds of waiters:
@@ -221,16 +221,10 @@ __condvar_switch_g1 (pthread_cond_t *cond, uint64_t wseq,
are not affected.
* Waiters in G1 have already received a signal and been woken. */
- /* Update __g1_start, which closes this group. The value we add will never
- be negative because old_orig_size can only be zero when we switch groups
- the first time after a condvar was initialized, in which case G1 will be
- at index 1 and we will add a value of 1. Relaxed MO is fine because the
- change comes with no additional constraints that others would have to
- observe. */
- __condvar_add_g1_start_relaxed (cond,
- (old_orig_size << 1) + (g1 == 1 ? 1 : - 1));
-
- unsigned int lowseq = ((old_g1_start + old_orig_size) << 1) & ~1U;
+ /* Update __g1_start, which closes this group. Relaxed MO is fine because
+ the change comes with no additional constraints that others would have
+ to observe. */
+ __condvar_add_g1_start_relaxed (cond, old_orig_size);
/* At this point, the old G1 is now a valid new G2 (but not in use yet).
No old waiter can neither grab a signal nor acquire a reference without
@@ -242,13 +236,13 @@ __condvar_switch_g1 (pthread_cond_t *cond, uint64_t wseq,
g1 ^= 1;
*g1index ^= 1;
- /* Now advance the new G1 g_signals to the new lowseq, giving it
+ /* Now advance the new G1 g_signals to the new g1_start, giving it
an effective signal count of 0 to start. */
- atomic_store_release (cond->__data.__g_signals + g1, lowseq);
+ atomic_store_release (cond->__data.__g_signals + g1, (unsigned)new_g1_start);
/* These values are just observed by signalers, and thus protected by the
lock. */
- unsigned int orig_size = wseq - (old_g1_start + old_orig_size);
+ unsigned int orig_size = wseq - new_g1_start;
__condvar_set_orig_size (cond, orig_size);
/* Use and addition to not loose track of cancellations in what was
previously G2. */
@@ -80,7 +80,7 @@ ___pthread_cond_signal (pthread_cond_t *cond)
release-MO store when initializing a group in __condvar_switch_g1
because we use an atomic read-modify-write and thus extend that
store's release sequence. */
- atomic_fetch_add_relaxed (cond->__data.__g_signals + g1, 2);
+ atomic_fetch_add_relaxed (cond->__data.__g_signals + g1, 1);
cond->__data.__g_size[g1]--;
/* TODO Only set it if there are indeed futex waiters. */
do_futex_wake = true;
@@ -84,7 +84,7 @@ __condvar_cancel_waiting (pthread_cond_t *cond, uint64_t seq, unsigned int g,
not hold a reference on the group. */
__condvar_acquire_lock (cond, private);
- uint64_t g1_start = __condvar_load_g1_start_relaxed (cond) >> 1;
+ uint64_t g1_start = __condvar_load_g1_start_relaxed (cond);
if (g1_start > seq)
{
/* Our group is closed, so someone provided enough signals for it.
@@ -259,7 +259,6 @@ __condvar_cleanup_waiting (void *arg)
* Waiters fetch-add while having acquire the mutex associated with the
condvar. Signalers load it and fetch-xor it concurrently.
__g1_start: Starting position of G1 (inclusive)
- * LSB is index of current G2.
* Modified by signalers while having acquired the condvar-internal lock
and observed concurrently by waiters.
__g1_orig_size: Initial size of G1
@@ -280,11 +279,9 @@ __condvar_cleanup_waiting (void *arg)
* Reference count used by waiters concurrently with signalers that have
acquired the condvar-internal lock.
__g_signals: The number of signals that can still be consumed, relative to
- the current g1_start. (i.e. bits 31 to 1 of __g_signals are bits
- 31 to 1 of g1_start with the signal count added)
+ the current g1_start. (i.e. g1_start with the signal count added)
* Used as a futex word by waiters. Used concurrently by waiters and
signalers.
- * LSB is currently reserved and 0.
__g_size: Waiters remaining in this group (i.e., which have not been
signaled yet.
* Accessed by signalers and waiters that cancel waiting (both do so only
@@ -391,9 +388,8 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
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;
- if (seq < (g1_start >> 1))
+ if (seq < g1_start)
{
/* If the group is closed already,
then this waiter originally had enough extra signals to
@@ -406,13 +402,13 @@ __pthread_cond_wait_common (pthread_cond_t *cond, pthread_mutex_t *mutex,
by now, perhaps in the process of switching back to an older
G2, but in either case we're allowed to consume the available
signal and should not block anymore. */
- if ((int)(signals - lowseq) >= 2)
+ if ((int)(signals - (unsigned int)g1_start) > 0)
{
/* 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))
+ &signals, signals - 1))
break;
else
continue;