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Add comment explaining HolderFromISR/SMP TOCTOU

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On SMP systems, xSemaphoreGetMutexHolderFromISR()
is particularly difficult to use - note the footgun.

See also espressif/esp-idf#18913
This commit is contained in:
Richard Allen 2026-09-04 10:29:58 -05:00
parent 8be86d4a24
commit 8db1d0d1a3
1 changed files with 1 additions and 0 deletions
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include/semphr.h
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@ -1157,6 +1157,7 @@ typedef QueueHandle_t SemaphoreHandle_t;
* If xMutex is not a mutex type semaphore, or the mutex is available (not held * If xMutex is not a mutex type semaphore, or the mutex is available (not held
* by a task), return NULL. * by a task), return NULL.
* *
* Note: On SMP systems, the return value may be invalidated by other core(s).
*/ */
#if ( ( configUSE_MUTEXES == 1 ) && ( INCLUDE_xSemaphoreGetMutexHolder == 1 ) ) #if ( ( configUSE_MUTEXES == 1 ) && ( INCLUDE_xSemaphoreGetMutexHolder == 1 ) )
#define xSemaphoreGetMutexHolderFromISR( xSemaphore ) xQueueGetMutexHolderFromISR( ( xSemaphore ) ) #define xSemaphoreGetMutexHolderFromISR( xSemaphore ) xQueueGetMutexHolderFromISR( ( xSemaphore ) )