pkarashchenko commented on code in PR #10752:
URL: https://github.com/apache/nuttx/pull/10752#discussion_r1335022806
##########
include/pthread.h:
##########
@@ -136,7 +136,7 @@
/* Used to initialize a pthread_once_t */
-#define PTHREAD_ONCE_INIT (false)
+#define PTHREAD_ONCE_INIT {false, PTHREAD_MUTEX_INITIALIZER}
Review Comment:
Also POSIX contains:
```
For dynamic library initialization in a multi-threaded process, if an
initialization flag is used the flag needs to be protected against modification
by multiple threads simultaneously calling into the library. This can be done
by using a mutex (initialized by assigning PTHREAD_MUTEX_INITIALIZER). However,
the better solution is to use pthread_once() which is designed for exactly this
purpose
```
So in this case I do not see a difference from `PTHREAD_MUTEX_INITIALIZER`
described case in POSIX
##########
libs/libc/pthread/pthread_once.c:
##########
@@ -75,23 +73,21 @@ int pthread_once(FAR pthread_once_t *once_control,
/* Prohibit pre-emption while we test and set the once_control. */
- nxrmutex_lock(&g_lock);
+ pthread_mutex_lock(&once_control->mutex);
- if (!*once_control)
+ if (!once_control->done)
{
- *once_control = true;
+ once_control->done = true;
Review Comment:
I think that `done` should be moved after `init_routine` to satisfy POSIX:
```
The pthread_once() function is not a cancellation point. However, if
init_routine is a cancellation point and is canceled, the effect on
once_control shall be as if pthread_once() was never called.
```
Also the question about calling a cancellation point API is still in place.
How do we release a mutex if the cancellation point API is called?
##########
libs/libc/pthread/pthread_once.c:
##########
@@ -75,23 +73,21 @@ int pthread_once(FAR pthread_once_t *once_control,
/* Prohibit pre-emption while we test and set the once_control. */
- nxrmutex_lock(&g_lock);
+ pthread_mutex_lock(&once_control->mutex);
- if (!*once_control)
+ if (!once_control->done)
{
- *once_control = true;
+ once_control->done = true;
Review Comment:
I think that `done` should be moved after `init_routine` to satisfy POSIX:
```
The pthread_once() function is not a cancellation point. However, if
init_routine is a cancellation point and is canceled, the effect on
once_control shall be as if pthread_once() was never called.
```
Also the question about calling a cancellation point API is still in place.
How do we release a mutex if the cancellation point API is called?
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