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[PATCH v2 1/3] sem-posix: remove the posix semaphore support
From: |
Longpeng(Mike) |
Subject: |
[PATCH v2 1/3] sem-posix: remove the posix semaphore support |
Date: |
Tue, 22 Feb 2022 17:05:04 +0800 |
POSIX specifies an absolute time for sem_timedwait(), it would be
affected if the system time is changing, but there is not a relative
time or monotonic clock version of sem_timedwait, so we cannot gain
from POSIX semaphore any more.
An alternative way is to use sem_trywait + usleep, maybe we can
remove CONFIG_SEM_TIMEDWAIT in this way? No, because some systems
(e.g. mac os) mark the sem_xxx API as deprecated.
So maybe remove the usage of POSIX semaphore and turn to use the
pthread variant for all systems looks better.
Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
---
include/qemu/thread-posix.h | 4 ----
meson.build | 1 -
util/qemu-thread-posix.c | 54 ---------------------------------------------
3 files changed, 59 deletions(-)
diff --git a/include/qemu/thread-posix.h b/include/qemu/thread-posix.h
index b792e6e..5466608 100644
--- a/include/qemu/thread-posix.h
+++ b/include/qemu/thread-posix.h
@@ -27,13 +27,9 @@ struct QemuCond {
};
struct QemuSemaphore {
-#ifndef CONFIG_SEM_TIMEDWAIT
pthread_mutex_t lock;
pthread_cond_t cond;
unsigned int count;
-#else
- sem_t sem;
-#endif
bool initialized;
};
diff --git a/meson.build b/meson.build
index 762d7ce..3ccb110 100644
--- a/meson.build
+++ b/meson.build
@@ -1557,7 +1557,6 @@ config_host_data.set('CONFIG_POSIX_FALLOCATE',
cc.has_function('posix_fallocate'
config_host_data.set('CONFIG_POSIX_MEMALIGN',
cc.has_function('posix_memalign'))
config_host_data.set('CONFIG_PPOLL', cc.has_function('ppoll'))
config_host_data.set('CONFIG_PREADV', cc.has_function('preadv', prefix:
'#include <sys/uio.h>'))
-config_host_data.set('CONFIG_SEM_TIMEDWAIT', cc.has_function('sem_timedwait',
dependencies: threads))
config_host_data.set('CONFIG_SENDFILE', cc.has_function('sendfile'))
config_host_data.set('CONFIG_SETNS', cc.has_function('setns') and
cc.has_function('unshare'))
config_host_data.set('CONFIG_SYNCFS', cc.has_function('syncfs'))
diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index e1225b6..1ad2503 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -219,7 +219,6 @@ void qemu_sem_init(QemuSemaphore *sem, int init)
{
int rc;
-#ifndef CONFIG_SEM_TIMEDWAIT
rc = pthread_mutex_init(&sem->lock, NULL);
if (rc != 0) {
error_exit(rc, __func__);
@@ -232,12 +231,6 @@ void qemu_sem_init(QemuSemaphore *sem, int init)
error_exit(EINVAL, __func__);
}
sem->count = init;
-#else
- rc = sem_init(&sem->sem, 0, init);
- if (rc < 0) {
- error_exit(errno, __func__);
- }
-#endif
sem->initialized = true;
}
@@ -247,7 +240,6 @@ void qemu_sem_destroy(QemuSemaphore *sem)
assert(sem->initialized);
sem->initialized = false;
-#ifndef CONFIG_SEM_TIMEDWAIT
rc = pthread_cond_destroy(&sem->cond);
if (rc < 0) {
error_exit(rc, __func__);
@@ -256,12 +248,6 @@ void qemu_sem_destroy(QemuSemaphore *sem)
if (rc < 0) {
error_exit(rc, __func__);
}
-#else
- rc = sem_destroy(&sem->sem);
- if (rc < 0) {
- error_exit(errno, __func__);
- }
-#endif
}
void qemu_sem_post(QemuSemaphore *sem)
@@ -269,7 +255,6 @@ void qemu_sem_post(QemuSemaphore *sem)
int rc;
assert(sem->initialized);
-#ifndef CONFIG_SEM_TIMEDWAIT
pthread_mutex_lock(&sem->lock);
if (sem->count == UINT_MAX) {
rc = EINVAL;
@@ -281,12 +266,6 @@ void qemu_sem_post(QemuSemaphore *sem)
if (rc != 0) {
error_exit(rc, __func__);
}
-#else
- rc = sem_post(&sem->sem);
- if (rc < 0) {
- error_exit(errno, __func__);
- }
-#endif
}
int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
@@ -295,7 +274,6 @@ int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
struct timespec ts;
assert(sem->initialized);
-#ifndef CONFIG_SEM_TIMEDWAIT
rc = 0;
compute_abs_deadline(&ts, ms);
pthread_mutex_lock(&sem->lock);
@@ -313,29 +291,6 @@ int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
}
pthread_mutex_unlock(&sem->lock);
return (rc == ETIMEDOUT ? -1 : 0);
-#else
- if (ms <= 0) {
- /* This is cheaper than sem_timedwait. */
- do {
- rc = sem_trywait(&sem->sem);
- } while (rc == -1 && errno == EINTR);
- if (rc == -1 && errno == EAGAIN) {
- return -1;
- }
- } else {
- compute_abs_deadline(&ts, ms);
- do {
- rc = sem_timedwait(&sem->sem, &ts);
- } while (rc == -1 && errno == EINTR);
- if (rc == -1 && errno == ETIMEDOUT) {
- return -1;
- }
- }
- if (rc < 0) {
- error_exit(errno, __func__);
- }
- return 0;
-#endif
}
void qemu_sem_wait(QemuSemaphore *sem)
@@ -343,7 +298,6 @@ void qemu_sem_wait(QemuSemaphore *sem)
int rc;
assert(sem->initialized);
-#ifndef CONFIG_SEM_TIMEDWAIT
pthread_mutex_lock(&sem->lock);
while (sem->count == 0) {
rc = pthread_cond_wait(&sem->cond, &sem->lock);
@@ -353,14 +307,6 @@ void qemu_sem_wait(QemuSemaphore *sem)
}
--sem->count;
pthread_mutex_unlock(&sem->lock);
-#else
- do {
- rc = sem_wait(&sem->sem);
- } while (rc == -1 && errno == EINTR);
- if (rc < 0) {
- error_exit(errno, __func__);
- }
-#endif
}
#ifdef __linux__
--
1.8.3.1