diff --git a/ports/linux/gnu/inc/tx_port.h b/ports/linux/gnu/inc/tx_port.h index 1f7e25f39..db837e4f9 100644 --- a/ports/linux/gnu/inc/tx_port.h +++ b/ports/linux/gnu/inc/tx_port.h @@ -511,7 +511,7 @@ VOID _tx_thread_interrupt_restore(UINT previous_posture); #define TX_RESTORE _tx_linux_debug_entry_insert("RESTORE", __FILE__, __LINE__); \ _tx_thread_interrupt_restore(tx_saved_posture); #endif /* TX_LINUX_DEBUG_ENABLE */ -#define tx_linux_mutex_lock(p) pthread_mutex_lock(&p) +#define tx_linux_mutex_lock(p) _tx_linux_mutex_lock_retry(&p) #define tx_linux_mutex_unlock(p) pthread_mutex_unlock(&p) #define tx_linux_mutex_recursive_unlock(p) {\ int _recursive_count = (int)tx_linux_mutex_recursive_count;\ @@ -552,6 +552,17 @@ extern CHAR _tx_version_id[]; /* Define externals for the Linux port of ThreadX. */ extern pthread_mutex_t _tx_linux_mutex; + +/* Define how long a thread waits on the Linux mutex before retrying. A thread + parked on the mutex can be suspended by the port's signal handler and so never + act on the wake-up the next unlock sends it, which leaves the wake-up lost and + every other waiter parked on a mutex that is free. */ + +#ifndef TX_LINUX_MUTEX_RETRY_NSEC +#define TX_LINUX_MUTEX_RETRY_NSEC 1000000 +#endif + +void _tx_linux_mutex_lock_retry(pthread_mutex_t *mutex); extern sem_t _tx_linux_semaphore; extern sem_t _tx_linux_semaphore_no_idle; extern ULONG _tx_linux_global_int_disabled_flag; diff --git a/ports/linux/gnu/src/tx_thread_schedule.c b/ports/linux/gnu/src/tx_thread_schedule.c index eeff680fc..405ef4b87 100644 --- a/ports/linux/gnu/src/tx_thread_schedule.c +++ b/ports/linux/gnu/src/tx_thread_schedule.c @@ -9,6 +9,8 @@ * SPDX-License-Identifier: MIT **************************************************************************/ +// Portions of this file were generated with AI assistance. + /**************************************************************************/ /**************************************************************************/ @@ -201,6 +203,49 @@ struct timespec ts; } } +/* Define the ThreadX Linux mutex lock function. The wait is timed and retried + rather than left to pthread_mutex_lock, because a thread can be signalled into + the port's suspend handler while it is parked on this mutex. That handler does + not return until the thread is resumed, so the wake-up the next unlock sends is + delivered to a thread that never retries and is lost. Any other thread parked + on the mutex then waits on a mutex that is free. Retrying on a timeout costs + nothing when the mutex is handed over normally, and turns that lost wake-up into + a delay of at most the retry period. */ + +void _tx_linux_mutex_lock_retry(pthread_mutex_t *mutex) +{ + +INT linux_status; +struct timespec ts; + + + do + { + + /* Set the deadline for this attempt. */ + clock_gettime(CLOCK_REALTIME, &ts); + ts.tv_nsec = ts.tv_nsec + TX_LINUX_MUTEX_RETRY_NSEC; + if (ts.tv_nsec >= 1000000000) + { + + ts.tv_nsec = ts.tv_nsec - 1000000000; + ts.tv_sec++; + } + + linux_status = pthread_mutex_timedlock(mutex, &ts); + + /* Anything but the deadline expiring is a real failure to obtain the + mutex, so stop retrying. */ + if ((linux_status != 0) && (linux_status != ETIMEDOUT)) + { + + break; + } + + } while (linux_status != 0); +} + + void _tx_thread_delete_port_completion(TX_THREAD *thread_ptr, UINT tx_saved_posture) { INT linux_status;