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Posted to commits@nuttx.apache.org by ac...@apache.org on 2025/07/08 12:47:52 UTC
(nuttx) 02/02: libc/semaphore: Go the fast path even arch doesn't support atomic
This is an automated email from the ASF dual-hosted git repository.
acassis pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/nuttx.git
commit 4c7366045ce3381384d63f14e153a320a2e7e363
Author: Xiang Xiao <xi...@xiaomi.com>
AuthorDate: Sun Jun 22 03:21:23 2025 +0800
libc/semaphore: Go the fast path even arch doesn't support atomic
since the simulated atomic operation is still fast than the slow path
Signed-off-by: Xiang Xiao <xi...@xiaomi.com>
---
libs/libc/semaphore/sem_post.c | 21 +++++----------------
libs/libc/semaphore/sem_trywait.c | 22 +++++-----------------
libs/libc/semaphore/sem_wait.c | 21 +++++----------------
3 files changed, 15 insertions(+), 49 deletions(-)
diff --git a/libs/libc/semaphore/sem_post.c b/libs/libc/semaphore/sem_post.c
index d34b6fea566..363b46fc9d0 100644
--- a/libs/libc/semaphore/sem_post.c
+++ b/libs/libc/semaphore/sem_post.c
@@ -119,37 +119,30 @@ int sem_post(FAR sem_t *sem)
int nxsem_post(FAR sem_t *sem)
{
- bool mutex;
bool fastpath = true;
+ bool mutex;
DEBUGASSERT(sem != NULL);
- /* We don't do atomic fast path in case of LIBC_ARCH_ATOMIC because that
- * uses spinlocks, which can't be called from userspace. Also in the kernel
- * taking the slow path directly is faster than locking first in here
- */
-
-#ifndef CONFIG_LIBC_ARCH_ATOMIC
-
mutex = NXSEM_IS_MUTEX(sem);
/* Disable fast path if priority protection is enabled on the semaphore */
-# ifdef CONFIG_PRIORITY_PROTECT
+#ifdef CONFIG_PRIORITY_PROTECT
if ((sem->flags & SEM_PRIO_MASK) == SEM_PRIO_PROTECT)
{
fastpath = false;
}
-# endif
+#endif
/* Disable fast path on a counting semaphore with priority inheritance */
-# ifdef CONFIG_PRIORITY_INHERITANCE
+#ifdef CONFIG_PRIORITY_INHERITANCE
if (!mutex && (sem->flags & SEM_PRIO_MASK) != SEM_PRIO_NONE)
{
fastpath = false;
}
-# endif
+#endif
while (fastpath)
{
@@ -181,10 +174,6 @@ int nxsem_post(FAR sem_t *sem)
return OK;
}
}
-#else
- UNUSED(mutex);
- UNUSED(fastpath);
-#endif
return nxsem_post_slow(sem);
}
diff --git a/libs/libc/semaphore/sem_trywait.c b/libs/libc/semaphore/sem_trywait.c
index 8f1686ea023..8a62ac9bd88 100644
--- a/libs/libc/semaphore/sem_trywait.c
+++ b/libs/libc/semaphore/sem_trywait.c
@@ -107,8 +107,8 @@ int sem_trywait(FAR sem_t *sem)
int nxsem_trywait(FAR sem_t *sem)
{
- bool mutex;
bool fastpath = true;
+ bool mutex;
DEBUGASSERT(sem != NULL);
@@ -119,32 +119,25 @@ int nxsem_trywait(FAR sem_t *sem)
up_interrupt_context());
#endif
- /* We don't do atomic fast path in case of LIBC_ARCH_ATOMIC because that
- * uses spinlocks, which can't be called from userspace. Also in the kernel
- * taking the slow path directly is faster than locking first in here
- */
-
-#ifndef CONFIG_LIBC_ARCH_ATOMIC
-
mutex = NXSEM_IS_MUTEX(sem);
/* Disable fast path if priority protection is enabled on the semaphore */
-# ifdef CONFIG_PRIORITY_PROTECT
+#ifdef CONFIG_PRIORITY_PROTECT
if ((sem->flags & SEM_PRIO_MASK) == SEM_PRIO_PROTECT)
{
fastpath = false;
}
-# endif
+#endif
/* Disable fast path on a counting semaphore with priority inheritance */
-# ifdef CONFIG_PRIORITY_INHERITANCE
+#ifdef CONFIG_PRIORITY_INHERITANCE
if (!mutex && (sem->flags & SEM_PRIO_MASK) != SEM_PRIO_NONE)
{
fastpath = false;
}
-# endif
+#endif
while (fastpath)
{
@@ -177,10 +170,5 @@ int nxsem_trywait(FAR sem_t *sem)
}
}
-#else
- UNUSED(mutex);
- UNUSED(fastpath);
-#endif
-
return nxsem_trywait_slow(sem);
}
diff --git a/libs/libc/semaphore/sem_wait.c b/libs/libc/semaphore/sem_wait.c
index dca20eb4bd6..ca39cf6587a 100644
--- a/libs/libc/semaphore/sem_wait.c
+++ b/libs/libc/semaphore/sem_wait.c
@@ -135,8 +135,8 @@ errout_with_cancelpt:
int nxsem_wait(FAR sem_t *sem)
{
- bool mutex;
bool fastpath = true;
+ bool mutex;
DEBUGASSERT(sem != NULL);
@@ -147,32 +147,25 @@ int nxsem_wait(FAR sem_t *sem)
up_interrupt_context());
#endif
- /* We don't do atomic fast path in case of LIBC_ARCH_ATOMIC because that
- * uses spinlocks, which can't be called from userspace. Also in the kernel
- * taking the slow path directly is faster than locking first in here
- */
-
-#ifndef CONFIG_LIBC_ARCH_ATOMIC
-
mutex = NXSEM_IS_MUTEX(sem);
/* Disable fast path if priority protection is enabled on the semaphore */
-# ifdef CONFIG_PRIORITY_PROTECT
+#ifdef CONFIG_PRIORITY_PROTECT
if ((sem->flags & SEM_PRIO_MASK) == SEM_PRIO_PROTECT)
{
fastpath = false;
}
-# endif
+#endif
/* Disable fast path on a counting semaphore with priority inheritance */
-# ifdef CONFIG_PRIORITY_INHERITANCE
+#ifdef CONFIG_PRIORITY_INHERITANCE
if (!mutex && (sem->flags & SEM_PRIO_MASK) != SEM_PRIO_NONE)
{
fastpath = false;
}
-# endif
+#endif
while (fastpath)
{
@@ -204,10 +197,6 @@ int nxsem_wait(FAR sem_t *sem)
return OK;
}
}
-#else
- UNUSED(mutex);
- UNUSED(fastpath);
-#endif
return nxsem_wait_slow(sem);
}