semaphore: do not overwrite errno in sem_timedwait()

This patch fixes problem that the errno value was being overwritten by
subsequent actions so that the returned errno value was incorrect.
All credits should go to Gregory Nutt who wrote the original commit.

Change-Id: I6ed3177e471f3ecb7aa79ada88c64b3db867ec28
Signed-off-by: Gregory Nutt <gnutt@nuttx.org>
[Song: backported 127951e0 from NuttX]
Signed-off-by: EunBong Song <eunb.song@samsung.com>

diff --git a/os/kernel/semaphore/sem_timedwait.c b/os/kernel/semaphore/sem_timedwait.c
index 30d6fa0..e96902a 100644 (file)
--- a/os/kernel/semaphore/sem_timedwait.c
+++ b/os/kernel/semaphore/sem_timedwait.c
@@ -184,7 +184,7 @@ int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
        FAR struct tcb_s *rtcb = (FAR struct tcb_s *)g_readytorun.head;
        irqstate_t flags;
        int ticks;
-       int err;
+       int errcode;
        int ret = ERROR;
 
        DEBUGASSERT(up_interrupt_context() == false && rtcb->waitdog == NULL);
@@ -198,7 +198,7 @@ int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
 
 #ifdef CONFIG_DEBUG
        if (!abstime || !sem) {
-               err = EINVAL;
+               errcode = EINVAL;
                goto errout;
        }
 #endif
@@ -210,7 +210,7 @@ int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
 
        rtcb->waitdog = wd_create();
        if (!rtcb->waitdog) {
-               err = ENOMEM;
+               errcode = ENOMEM;
                goto errout;
        }
 
@@ -242,7 +242,7 @@ int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
         */
 
        if (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000) {
-               err = EINVAL;
+               errcode = EINVAL;
                goto errout_disabled;
        }
 
@@ -250,29 +250,34 @@ int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
         * disabled here so that this time stays valid until the wait begins.
         */
 
-       err = clock_abstime2ticks(CLOCK_REALTIME, abstime, &ticks);
+       errcode = clock_abstime2ticks(CLOCK_REALTIME, abstime, &ticks);
 
        /* If the time has already expired return immediately. */
 
-       if (err == OK && ticks <= 0) {
-               err = ETIMEDOUT;
+       if (errcode == OK && ticks <= 0) {
+               errcode = ETIMEDOUT;
                goto errout_disabled;
        }
 
        /* Handle any time-related errors */
 
-       if (err != OK) {
+       if (errcode != OK) {
                goto errout_disabled;
        }
 
        /* Start the watchdog */
 
-       err = OK;
+       errcode = OK;
        wd_start(rtcb->waitdog, ticks, (wdentry_t)sem_timeout, 1, getpid());
 
        /* Now perform the blocking wait */
 
        ret = sem_wait(sem);
+       if (ret < 0) {
+               /* sem_wait() failed.  Save the errno value */
+
+               errcode = get_errno();
+       }
 
        /* Stop the watchdog timer */
 
@@ -291,6 +296,12 @@ int sem_timedwait(FAR sem_t *sem, FAR const struct timespec *abstime)
         * cases.
         */
 
+       if (ret < 0) {
+               /* On failure, restore the errno value returned by sem_wait */
+
+               set_errno(errcode);
+       }
+
        return ret;
 
        /* Error exits */
@@ -301,7 +312,7 @@ errout_disabled:
        rtcb->waitdog = NULL;
 
 errout:
-       set_errno(err);
+       set_errno(errcode);
        leave_cancellation_point();
        return ERROR;
 }