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sync.c
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sync.c
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#include <errno.h>
#include <limits.h>
#include "kernel/task.h"
#include "util/sync.h"
#include "debug.h"
#include "kernel/errno.h"
void cond_init(cond_t *cond) {
pthread_condattr_t attr;
pthread_condattr_init(&attr);
#if __linux__
pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);
#endif
pthread_cond_init(&cond->cond, &attr);
}
void cond_destroy(cond_t *cond) {
pthread_cond_destroy(&cond->cond);
}
static bool is_signal_pending(lock_t *lock) {
if (!current)
return false;
if (lock != ¤t->sighand->lock)
lock(¤t->sighand->lock);
bool pending = !!(current->pending & ~current->blocked);
if (lock != ¤t->sighand->lock)
unlock(¤t->sighand->lock);
return pending;
}
int wait_for(cond_t *cond, lock_t *lock, struct timespec *timeout) {
if (is_signal_pending(lock))
return _EINTR;
int err = wait_for_ignore_signals(cond, lock, timeout);
if (err < 0)
return _ETIMEDOUT;
if (is_signal_pending(lock))
return _EINTR;
return 0;
}
int wait_for_ignore_signals(cond_t *cond, lock_t *lock, struct timespec *timeout) {
if (current) {
lock(¤t->waiting_cond_lock);
current->waiting_cond = cond;
current->waiting_lock = lock;
unlock(¤t->waiting_cond_lock);
}
int rc = 0;
#if LOCK_DEBUG
struct lock_debug lock_tmp = lock->debug;
lock->debug = (struct lock_debug) { .initialized = lock->debug.initialized };
#endif
if (!timeout) {
pthread_cond_wait(&cond->cond, &lock->m);
} else {
#if __linux__
struct timespec abs_timeout;
clock_gettime(CLOCK_MONOTONIC, &abs_timeout);
abs_timeout.tv_sec += timeout->tv_sec;
abs_timeout.tv_nsec += timeout->tv_nsec;
if (abs_timeout.tv_nsec > 1000000000) {
abs_timeout.tv_sec++;
abs_timeout.tv_nsec -= 1000000000;
}
rc = pthread_cond_timedwait(&cond->cond, &lock->m, &abs_timeout);
#elif __APPLE__
rc = pthread_cond_timedwait_relative_np(&cond->cond, &lock->m, timeout);
#else
#error Unimplemented pthread_cond_wait relative timeout.
#endif
}
#if LOCK_DEBUG
lock->debug = lock_tmp;
#endif
if (current) {
lock(¤t->waiting_cond_lock);
current->waiting_cond = NULL;
current->waiting_lock = NULL;
unlock(¤t->waiting_cond_lock);
}
if (rc == ETIMEDOUT)
return _ETIMEDOUT;
return 0;
}
void notify(cond_t *cond) {
pthread_cond_broadcast(&cond->cond);
}
void notify_once(cond_t *cond) {
pthread_cond_signal(&cond->cond);
}
__thread sigjmp_buf unwind_buf;
__thread bool should_unwind = false;
void sigusr1_handler() {
if (should_unwind) {
should_unwind = false;
siglongjmp(unwind_buf, 1);
}
}
// This is how you would mitigate the unlock/wait race if the wait
// is async signal safe. wait_for *should* be safe from this race
// because of synchronization involving the waiting_cond_lock.
#if 0
sigset_t sigusr1;
sigemptyset(&sigusr1);
sigaddset(&sigusr1, SIGUSR1);
if (current) {
if (sigsetjmp(unwind_buf, 1)) {
return _EINTR;
}
should_unwind = true;
sigprocmask(SIG_BLOCK, &sigusr1, NULL);
if (lock != ¤t->sighand->lock)
lock(¤t->sighand->lock);
bool pending = !!(current->pending & ~current->blocked);
if (lock != ¤t->sighand->lock)
unlock(¤t->sighand->lock);
sigprocmask(SIG_UNBLOCK, &sigusr1, NULL);
if (pending) {
should_unwind = false;
return _EINTR;
}
}
#endif