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authorRich Felker <dalias@aerifal.cx>2011-04-06 12:24:34 -0400
committerRich Felker <dalias@aerifal.cx>2011-04-06 12:24:34 -0400
commita113434cd68ce30642c4995b1caadcd084be6f09 (patch)
treeb26daaeda2c9e2caf1605615c497a4a84191e01d /src/thread
parentcd3bb38412cfcc3bc47985ba25287e0af463609a (diff)
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major semaphore improvements (performance and correctness)
1. make sem_[timed]wait interruptible by signals, per POSIX 2. keep a waiter count in order to avoid unnecessary futex wake syscalls
Diffstat (limited to 'src/thread')
-rw-r--r--src/thread/__timedwait.c2
-rw-r--r--src/thread/pthread_cond_timedwait.c3
-rw-r--r--src/thread/sem_post.c3
-rw-r--r--src/thread/sem_timedwait.c45
-rw-r--r--src/thread/sem_trywait.c5
5 files changed, 37 insertions, 21 deletions
diff --git a/src/thread/__timedwait.c b/src/thread/__timedwait.c
index 28b777bc..a673099b 100644
--- a/src/thread/__timedwait.c
+++ b/src/thread/__timedwait.c
@@ -18,6 +18,6 @@ int __timedwait(volatile int *addr, int val, clockid_t clk, const struct timespe
}
if (priv) priv = 128; priv=0;
r = -__syscall(__NR_futex, (long)addr, FUTEX_WAIT | priv, val, at ? (long)&to : 0);
- if (r == ETIMEDOUT) return r;
+ if (r == ETIMEDOUT || r == EINTR) return r;
return 0;
}
diff --git a/src/thread/pthread_cond_timedwait.c b/src/thread/pthread_cond_timedwait.c
index 1439aace..7a19fc55 100644
--- a/src/thread/pthread_cond_timedwait.c
+++ b/src/thread/pthread_cond_timedwait.c
@@ -16,7 +16,8 @@ int pthread_cond_timedwait(pthread_cond_t *c, pthread_mutex_t *m, const struct t
if ((r=pthread_mutex_unlock(m))) return r;
CANCELPT_BEGIN;
- e = __timedwait(&c->_c_block, 1, c->_c_clock, ts, 0);
+ do e = __timedwait(&c->_c_block, 1, c->_c_clock, ts, 0);
+ while (e == EINTR);
CANCELPT_END;
pthread_cleanup_pop(0);
diff --git a/src/thread/sem_post.c b/src/thread/sem_post.c
index 0bd8a462..8f4700c3 100644
--- a/src/thread/sem_post.c
+++ b/src/thread/sem_post.c
@@ -3,7 +3,8 @@
int sem_post(sem_t *sem)
{
- if (!a_fetch_add(sem->__val, 1))
+ a_inc(sem->__val);
+ if (sem->__val[1])
__wake(sem->__val, 1, 0);
return 0;
}
diff --git a/src/thread/sem_timedwait.c b/src/thread/sem_timedwait.c
index 11a01700..4f45c172 100644
--- a/src/thread/sem_timedwait.c
+++ b/src/thread/sem_timedwait.c
@@ -1,26 +1,41 @@
#include <semaphore.h>
#include "pthread_impl.h"
+static void cleanup(void *p)
+{
+ a_dec(p);
+}
+
int sem_timedwait(sem_t *sem, const struct timespec *at)
{
- int val;
+ int r;
+
+ if (a_fetch_add(sem->__val, -1) > 0) return 0;
+ a_inc(sem->__val);
+
+ if (at && at->tv_nsec >= 1000000000UL) {
+ errno = EINVAL;
+ return -1;
+ }
+
+ a_inc(sem->__val+1);
+ pthread_cleanup_push(cleanup, sem->__val+1)
+ CANCELPT_BEGIN;
for (;;) {
- if (a_fetch_add(sem->__val, -1) > 0) return 0;
- val = a_fetch_add(sem->__val, 1)+1;
- if (val==1) __wake(sem->__val, 1, 0);
- if (at && at->tv_nsec >= 1000000000UL) {
- errno = EINVAL;
- return -1;
- }
- CANCELPT_BEGIN;
- if (val <= 0 && __timedwait(sem->__val, val, CLOCK_REALTIME, at, 0) == ETIMEDOUT) {
- errno = ETIMEDOUT;
- CANCELPT_TRY;
- CANCELPT_END;
- return -1;
+ r = 0;
+ if (!sem_trywait(sem)) break;
+ r = __timedwait(sem->__val, 0, CLOCK_REALTIME, at, 0);
+ if (r) {
+ errno = r;
+ r = -1;
+ break;
}
CANCELPT_TRY;
- CANCELPT_END;
}
+ CANCELPT_END;
+
+ pthread_cleanup_pop(1);
+
+ return r;
}
diff --git a/src/thread/sem_trywait.c b/src/thread/sem_trywait.c
index c5370c70..beb7aa5d 100644
--- a/src/thread/sem_trywait.c
+++ b/src/thread/sem_trywait.c
@@ -3,9 +3,8 @@
int sem_trywait(sem_t *sem)
{
- int val = a_fetch_add(sem->__val, -1);
- if (val > 0) return 0;
- if (!a_fetch_add(sem->__val, 1))
+ if (a_fetch_add(sem->__val, -1) > 0) return 0;
+ if (!a_fetch_add(sem->__val, 1) && sem->__val[1])
__wake(sem->__val, 1, 0);
errno = EAGAIN;
return -1;