Files
esp-idf/components/linux/lock.c
Guillaume Souchere 445db75612 fix(linux): implement pthread-based locks for soft-preemption safety
The Linux target's sys/lock.h provided no-op inline stubs, which was
safe only under the assumption of single-threaded execution.  With the
new FreeRTOS Linux simulator using soft preemption, an outgoing task
can still run concurrently with the incoming task until it reaches a
yield point, making no-op locks unsafe.

Replace the no-op implementation with real pthread mutexes:

- Change _lock_t from `typedef int` to `typedef void *` (pointer to a
  heap-allocated pthread_mutex_t).
- Implement all _lock_* functions in a new lock.c, supporting both
  normal and recursive mutexes.
- Zero-initialized locks are lazily created on first acquire using
  double-checked locking, preserving newlib/esp_libc semantics.
- Add lock.c unconditionally to the linux component sources and link
  pthread.
2026-06-04 11:36:34 +02:00

108 lines
2.4 KiB
C

/*
* SPDX-FileCopyrightText: 2026 Espressif Systems (Shanghai) CO LTD
*
* SPDX-License-Identifier: Apache-2.0
*/
#include <sys/lock.h>
#include <stdlib.h>
#include <pthread.h>
/*
* Protects lazy initialization of locks that were zero-initialized
* (e.g. static _lock_t my_lock = 0;). Two threads calling
* _lock_acquire on such a lock race to create the underlying mutex;
* this guard serialises the creation.
*/
static pthread_mutex_t s_lock_init_guard = PTHREAD_MUTEX_INITIALIZER;
static void lock_init_generic(_lock_t *plock, int recursive)
{
pthread_mutexattr_t attr;
pthread_mutexattr_init(&attr);
if (recursive) {
pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
}
pthread_mutex_t *m = calloc(1, sizeof(pthread_mutex_t));
if (m == NULL) {
pthread_mutexattr_destroy(&attr);
abort();
}
pthread_mutex_init(m, &attr);
pthread_mutexattr_destroy(&attr);
*plock = (_lock_t)m;
}
static void lazy_init(_lock_t *plock, int recursive)
{
if (__atomic_load_n(plock, __ATOMIC_ACQUIRE) == NULL) {
pthread_mutex_lock(&s_lock_init_guard);
if (*plock == NULL) {
lock_init_generic(plock, recursive);
}
pthread_mutex_unlock(&s_lock_init_guard);
}
}
void _lock_init(_lock_t *plock)
{
*plock = NULL;
lock_init_generic(plock, 0);
}
void _lock_init_recursive(_lock_t *plock)
{
*plock = NULL;
lock_init_generic(plock, 1);
}
void _lock_close(_lock_t *plock)
{
if (*plock) {
pthread_mutex_destroy((pthread_mutex_t *)(*plock));
free(*plock);
*plock = NULL;
}
}
void _lock_close_recursive(_lock_t *plock)
{
_lock_close(plock);
}
void _lock_acquire(_lock_t *plock)
{
lazy_init(plock, 0);
pthread_mutex_lock((pthread_mutex_t *)(*plock));
}
void _lock_acquire_recursive(_lock_t *plock)
{
lazy_init(plock, 1);
pthread_mutex_lock((pthread_mutex_t *)(*plock));
}
int _lock_try_acquire(_lock_t *plock)
{
lazy_init(plock, 0);
return (pthread_mutex_trylock((pthread_mutex_t *)(*plock)) == 0) ? 0 : -1;
}
int _lock_try_acquire_recursive(_lock_t *plock)
{
lazy_init(plock, 1);
return (pthread_mutex_trylock((pthread_mutex_t *)(*plock)) == 0) ? 0 : -1;
}
void _lock_release(_lock_t *plock)
{
if (*plock) {
pthread_mutex_unlock((pthread_mutex_t *)(*plock));
}
}
void _lock_release_recursive(_lock_t *plock)
{
_lock_release(plock);
}