jlaitine commented on code in PR #16030:
URL: https://github.com/apache/nuttx/pull/16030#discussion_r2007915286
##########
include/nuttx/semaphore.h:
##########
@@ -59,6 +59,56 @@
{(c), (f), SEM_WAITLIST_INITIALIZER}
#endif /* CONFIG_PRIORITY_INHERITANCE */
+/* Fast mutex lock/unlock path */
+
+#ifndef CONFIG_LIBC_ARCH_ATOMIC
+
+# if defined(CONFIG_PRIORITY_PROTECT) || defined(CONFIG_PRIORITY_INHERITANCE)
+# define NXSEM_IS_FASTMUTEX(sem) \
+ (((sem)->flags & (SEM_TYPE_MUTEX | SEM_PRIO_MASK)) == \
+ (SEM_TYPE_MUTEX | SEM_PRIO_NONE))
+# else
+# define NXSEM_IS_FASTMUTEX(sem) ((sem)->flags & SEM_TYPE_MUTEX)
+# endif
+
+/* Try wait; sets ret to OK or -EAGAIN when success,
+ * -EPERM when fast locking can't be performed
+ */
+
+# define NXSEM_TRYWAIT_FAST(sem, ret) \
+ { \
+ (ret) = -EPERM; \
+ if (NXSEM_IS_FASTMUTEX(sem)) \
+ { \
+ int32_t old = 1; \
+ (ret) = atomic_try_cmpxchg_acquire(NXSEM_COUNT(sem), &old, 0) ? \
+ OK : -EAGAIN; \
+ } \
+ }
+
+/* Post; sets ret to OK when success and -EPERM when
+ * fast posting can't be performed
+ */
+
+# define NXSEM_POST_FAST(sem, ret) \
+ { \
+ (ret) = -EPERM; \
+ if (NXSEM_IS_FASTMUTEX(sem)) \
+ { \
+ int32_t old = 0; \
Review Comment:
Semaphore counter is of type int32_t, so that is the correct type for atomic
exchange. Actually even build would fail if int size is different than sem
counter size (can't obviously exchange 32bit and 16bit values)
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