make thread killlock async-signal-safe for pthread_kill

pthread_kill is required to be AS-safe. that requirement can't be met
if the target thread's killlock can be taken in contexts where
application-installed signal handlers can run.

block signals around use of this lock in all pthread_* functions which
target a tid, and reorder blocking/unblocking of signals in
pthread_exit so that they're blocked whenever the killlock is held.

diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c
index 6bdfb44..10f1b7d 100644 (file)
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -72,12 +72,13 @@ _Noreturn void __pthread_exit(void *result)
        /* Access to target the exiting thread with syscalls that use
         * its kernel tid is controlled by killlock. For detached threads,
         * any use past this point would have undefined behavior, but for
-        * joinable threads it's a valid usage that must be handled. */
+        * joinable threads it's a valid usage that must be handled.
+        * Signals must be blocked since pthread_kill must be AS-safe. */
+       __block_app_sigs(&set);
        LOCK(self->killlock);
 
-       /* The thread list lock must be AS-safe, and thus requires
-        * application signals to be blocked before it can be taken. */
-       __block_app_sigs(&set);
+       /* The thread list lock must be AS-safe, and thus depends on
+        * application signals being blocked above. */
        __tl_lock();
 
        /* If this is the only thread in the list, don't proceed with
@@ -85,8 +86,8 @@ _Noreturn void __pthread_exit(void *result)
         * signal state to prepare for exit to call atexit handlers. */
        if (self->next == self) {
                __tl_unlock();
-               __restore_sigs(&set);
                UNLOCK(self->killlock);
+               __restore_sigs(&set);
                exit(0);
        }
 

diff --git a/src/thread/pthread_getschedparam.c b/src/thread/pthread_getschedparam.c
index 1cba073..c098bef 100644 (file)
--- a/src/thread/pthread_getschedparam.c
+++ b/src/thread/pthread_getschedparam.c
@@ -4,6 +4,8 @@
 int pthread_getschedparam(pthread_t t, int *restrict policy, struct sched_param *restrict param)
 {
        int r;
+       sigset_t set;
+       __block_app_sigs(&set);
        LOCK(t->killlock);
        if (!t->tid) {
                r = ESRCH;
@@ -14,5 +16,6 @@ int pthread_getschedparam(pthread_t t, int *restrict policy, struct sched_param
                }
        }
        UNLOCK(t->killlock);
+       __restore_sigs(&set);
        return r;
 }

diff --git a/src/thread/pthread_kill.c b/src/thread/pthread_kill.c
index 3d9395c..446254b 100644 (file)
--- a/src/thread/pthread_kill.c
+++ b/src/thread/pthread_kill.c
@@ -4,9 +4,12 @@
 int pthread_kill(pthread_t t, int sig)
 {
        int r;
+       sigset_t set;
+       __block_app_sigs(&set);
        LOCK(t->killlock);
        r = t->tid ? -__syscall(SYS_tkill, t->tid, sig)
                : (sig+0U >= _NSIG ? EINVAL : 0);
        UNLOCK(t->killlock);
+       __restore_sigs(&set);
        return r;
 }

diff --git a/src/thread/pthread_setschedparam.c b/src/thread/pthread_setschedparam.c
index 038d13d..76d4d45 100644 (file)
--- a/src/thread/pthread_setschedparam.c
+++ b/src/thread/pthread_setschedparam.c
@@ -4,8 +4,11 @@
 int pthread_setschedparam(pthread_t t, int policy, const struct sched_param *param)
 {
        int r;
+       sigset_t set;
+       __block_app_sigs(&set);
        LOCK(t->killlock);
        r = !t->tid ? ESRCH : -__syscall(SYS_sched_setscheduler, t->tid, policy, param);
        UNLOCK(t->killlock);
+       __restore_sigs(&set);
        return r;
 }

diff --git a/src/thread/pthread_setschedprio.c b/src/thread/pthread_setschedprio.c
index 5bf4a01..fc2e13d 100644 (file)
--- a/src/thread/pthread_setschedprio.c
+++ b/src/thread/pthread_setschedprio.c
@@ -4,8 +4,11 @@
 int pthread_setschedprio(pthread_t t, int prio)
 {
        int r;
+       sigset_t set;
+       __block_app_sigs(&set);
        LOCK(t->killlock);
        r = !t->tid ? ESRCH : -__syscall(SYS_sched_setparam, t->tid, &prio);
        UNLOCK(t->killlock);
+       __restore_sigs(&set);
        return r;
 }