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// SPDX-License-Identifier: GPL-2.0
#include "mutex.h"
#include "debug.h"
#include <linux/string.h>
#include <errno.h>
static void check_err(const char *fn, int err)
{
char sbuf[STRERR_BUFSIZE];
if (err == 0)
return;
pr_err("%s error: '%s'\n", fn, str_error_r(err, sbuf, sizeof(sbuf)));
}
#define CHECK_ERR(err) check_err(__func__, err)
#ifdef HAVE_PTHREAD_MUTEX_ROBUST
/*
* A robust mutex whose owner died while holding it comes back as EOWNERDEAD,
* with the caller holding it: make it consistent, which takes it over; failing
* that, a give_up caller unlocks it, leaving it ENOTRECOVERABLE, not leaked.
*/
static int mutex_take_over(struct mutex *mtx, int err, bool give_up)
{
if (err != EOWNERDEAD)
return err;
pr_debug("mutex: taking over one left by a dead owner\n");
err = pthread_mutex_consistent(&mtx->lock);
if (err && give_up)
CHECK_ERR(pthread_mutex_unlock(&mtx->lock));
return err;
}
#else
#define mutex_take_over(mtx, err, give_up) ((void)(mtx), (void)(give_up), (err))
#endif
static bool __mutex_init(struct mutex *mtx, bool pshared, bool recursive, bool robust)
{
pthread_mutexattr_t attr;
bool ok = false, robust_unavailable = false;
int err;
err = pthread_mutexattr_init(&attr);
if (err)
goto out;
#ifndef NDEBUG
/* In normal builds enable error checking, such as recursive usage. */
err = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_ERRORCHECK);
if (err)
goto out_destroy;
#endif
if (recursive) {
err = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
if (err)
goto out_destroy;
}
if (pshared) {
err = pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED);
if (err)
goto out_destroy;
}
if (robust) {
#ifdef HAVE_PTHREAD_MUTEX_ROBUST
err = pthread_mutexattr_setrobust(&attr, PTHREAD_MUTEX_ROBUST);
if (err)
robust_unavailable = true;
#else
robust_unavailable = true;
#endif
if (robust_unavailable)
goto out_destroy;
}
err = pthread_mutex_init(&mtx->lock, &attr);
if (!err)
ok = true;
else if (robust && pshared && err == ENOTSUP)
/*
* glibc refuses a robust process shared mutex with ENOTSUP when
* set_robust_list(2) isn't usable, i.e. when the machine provides
* no robust mutexes for the process shared case: an unavailable
* API, not a bad request.
*/
robust_unavailable = true;
out_destroy:
CHECK_ERR(pthread_mutexattr_destroy(&attr));
out:
if (robust_unavailable)
pr_debug("mutex: robust mutexes aren't available\n");
else if (err)
CHECK_ERR(err);
return ok;
}
void mutex_init(struct mutex *mtx)
{
__mutex_init(mtx, /*pshared=*/false, /*recursive=*/false, /*robust=*/false);
}
void mutex_init_pshared(struct mutex *mtx)
{
__mutex_init(mtx, /*pshared=*/true, /*recursive=*/false, /*robust=*/false);
}
void mutex_init_recursive(struct mutex *mtx)
{
__mutex_init(mtx, /*pshared=*/false, /*recursive=*/true, /*robust=*/false);
}
bool mutex_init_pshared_robust(struct mutex *mtx)
{
return __mutex_init(mtx, /*pshared=*/true, /*recursive=*/false, /*robust=*/true);
}
void mutex_destroy(struct mutex *mtx)
{
CHECK_ERR(pthread_mutex_destroy(&mtx->lock));
}
void mutex_lock(struct mutex *mtx)
NO_THREAD_SAFETY_ANALYSIS
{
CHECK_ERR(mutex_take_over(mtx, pthread_mutex_lock(&mtx->lock),
/*give_up=*/false));
}
void mutex_unlock(struct mutex *mtx)
NO_THREAD_SAFETY_ANALYSIS
{
CHECK_ERR(pthread_mutex_unlock(&mtx->lock));
}
bool mutex_trylock(struct mutex *mtx)
{
int ret = mutex_take_over(mtx, pthread_mutex_trylock(&mtx->lock),
/*give_up=*/true);
if (ret == 0)
return true; /* Lock acquired. */
if (ret == EBUSY)
return false; /* Lock busy. */
/* Print error. */
CHECK_ERR(ret);
return false;
}
static void __cond_init(struct cond *cnd, bool pshared)
{
pthread_condattr_t attr;
CHECK_ERR(pthread_condattr_init(&attr));
if (pshared)
CHECK_ERR(pthread_condattr_setpshared(&attr, PTHREAD_PROCESS_SHARED));
CHECK_ERR(pthread_cond_init(&cnd->cond, &attr));
CHECK_ERR(pthread_condattr_destroy(&attr));
}
void cond_init(struct cond *cnd)
{
__cond_init(cnd, /*pshared=*/false);
}
void cond_init_pshared(struct cond *cnd)
{
__cond_init(cnd, /*pshared=*/true);
}
void cond_destroy(struct cond *cnd)
{
CHECK_ERR(pthread_cond_destroy(&cnd->cond));
}
void cond_wait(struct cond *cnd, struct mutex *mtx)
{
CHECK_ERR(mutex_take_over(mtx,
pthread_cond_wait(&cnd->cond, &mtx->lock),
/*give_up=*/false));
}
void cond_signal(struct cond *cnd)
{
CHECK_ERR(pthread_cond_signal(&cnd->cond));
}
void cond_broadcast(struct cond *cnd)
{
CHECK_ERR(pthread_cond_broadcast(&cnd->cond));
}
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