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Fix deadlock issues with signals: block all signals while inside mutex.

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Mathis Beer
2020-03-03 16:39:42 +01:00
parent fe8c0acee6
commit 052239d828
1 changed files with 26 additions and 5 deletions
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31
src/libfaketime.c
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@@ -53,6 +53,7 @@
/* pthread-handling contributed by David North, TDI in version 0.7 */
#if defined PTHREAD_SINGLETHREADED_TIME || defined FAKE_PTHREAD
#include <pthread.h>
#include <signal.h>
#endif
#include <sys/timeb.h>
@@ -2619,10 +2620,24 @@ static void remove_trailing_eols(char *line)
*/
#ifdef PTHREAD_SINGLETHREADED_TIME
/*
* To avoid a deadlock if a faketime function is interrupted by a signal while
* holding the lock, we block all signals while the mutex is locked.
* The original_mask field is used to restore the previous set of signals
* after the lock has been released.
* (Prompted by issues with parallel garbage collection in D 2.090. D uses signals
* to freeze all but one thread. The frozen threads may be in faketime operations.)
*/
struct LockedState {
pthread_mutex_t mutex;
sigset_t original_mask;
};
static void pthread_cleanup_mutex_lock(void *data)
{
pthread_mutex_t *mutex = data;
pthread_mutex_unlock(mutex);
struct LockedState *state = data;
pthread_mutex_unlock(&state->mutex);
sigprocmask(SIG_SETMASK, &state->original_mask, NULL);
}
#endif
@@ -2652,9 +2667,15 @@ int fake_clock_gettime(clockid_t clk_id, struct timespec *tp)
if (tp == NULL) return -1;
#ifdef PTHREAD_SINGLETHREADED_TIME
static pthread_mutex_t time_mutex=PTHREAD_MUTEX_INITIALIZER;
pthread_mutex_lock(&time_mutex);
pthread_cleanup_push(pthread_cleanup_mutex_lock, &time_mutex);
static struct LockedState state = { 0 };
// block all signals while locked. prevents deadlocks if signal interrupts in in mid-operation.
sigset_t all_signals;
sigfillset(&all_signals);
sigprocmask(SIG_SETMASK, &all_signals, &state.original_mask);
pthread_mutex_lock(&state.mutex);
pthread_cleanup_push(pthread_cleanup_mutex_lock, &state);
#endif
if ((limited_faking &&