From f9fc8932b11f3bcf2a2626f567cb6fdd36a33a94 Mon Sep 17 00:00:00 2001
From: "Longpeng(Mike)" <longpeng2@huawei.com>
Date: Tue, 22 Feb 2022 17:05:04 +0800
Subject: thread-posix: remove the posix semaphore support

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>
Message-Id: <20220222090507.2028-2-longpeng2@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 util/qemu-thread-posix.c | 54 ------------------------------------------------
 1 file changed, 54 deletions(-)

(limited to 'util/qemu-thread-posix.c')

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__
-- 
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