use a separate signal from SIGCANCEL for SIGEV_THREAD timers

otherwise we cannot support an application's desire to use
asynchronous cancellation within the callback function. this change
also slightly debloats pthread_create.c.

src/internal/pthread_impl.h

@@ -76,6 +76,7 @@ struct __timer {
 
 #define SIGCANCEL 32
 #define SIGSYSCALL 33
+#define SIGTIMER 34
 
 int __set_thread_area(void *);
 int __libc_sigaction(int, const struct sigaction *, struct sigaction *);

src/signal/sigaction.c

@@ -35,7 +35,7 @@ int __libc_sigaction(int sig, const struct sigaction *sa, struct sigaction *old)
 
 int __sigaction(int sig, const struct sigaction *sa, struct sigaction *old)
 {
-	if (sig == SIGCANCEL || sig == SIGSYSCALL) {
+	if (sig-SIGCANCEL < 3U) {
 		errno = EINVAL;
 		return -1;
 	}

src/signal/sigprocmask.c

@@ -22,6 +22,7 @@ int __sigprocmask(int how, const sigset_t *set, sigset_t *old)
 		set = &tmp;
 		sigdelset(&tmp, SIGCANCEL);
 		sigdelset(&tmp, SIGSYSCALL);
+		sigdelset(&tmp, SIGTIMER);
 	}
 	return __libc_sigprocmask(how, set, old);
 }

src/signal/sigrtmin.c

@@ -1,4 +1,4 @@
 int __libc_current_sigrtmin()
 {
-	return 34;
+	return 35;
 }

src/thread/pthread_create.c

@@ -10,7 +10,6 @@ static void dummy_1(pthread_t self)
 {
 }
 weak_alias(dummy_1, __pthread_tsd_run_dtors);
-weak_alias(dummy_1, __sigtimer_handler);
 
 #ifdef __pthread_unwind_next
 #undef __pthread_unwind_next
@@ -54,7 +53,6 @@ static void docancel(struct pthread *self)
 static void cancel_handler(int sig, siginfo_t *si, void *ctx)
 {
 	struct pthread *self = __pthread_self();
-	if (si->si_code == SI_TIMER) __sigtimer_handler(self);
 	if (self->cancel && !self->canceldisable &&
 	    (self->cancelasync || (self->cancelpoint==1 && PC_AT_SYS(ctx))))
 		docancel(self);

src/time/timer_create.c

@@ -21,22 +21,38 @@ weak_alias(dummy_1, __pthread_tsd_run_dtors);
 static void cleanup_fromsig(void *p)
 {
 	pthread_t self = __pthread_self();
+	__pthread_tsd_run_dtors(self);
 	self->cancel = 0;
 	self->cancelbuf = 0;
-	__pthread_tsd_run_dtors(self);
+	self->canceldisable = 0;
+	self->cancelasync = 0;
+	self->unblock_cancel = 0;
 	longjmp(p, 1);
 }
 
-void __sigtimer_handler(pthread_t self)
+static void timer_handler(int sig, siginfo_t *si, void *ctx)
 {
+	pthread_t self = __pthread_self();
 	jmp_buf jb;
 	void (*notify)(union sigval) = (void (*)(union sigval))self->start;
 	union sigval val = { .sival_ptr = self->start_arg };
 
-	if (setjmp(jb)) return;
+	if (!setjmp(jb) && si->si_code == SI_TIMER) {
 		pthread_cleanup_push(cleanup_fromsig, jb);
 		notify(val);
 		pthread_cleanup_pop(0);
+	}
+}
+
+static void install_handler()
+{
+	struct sigaction sa = {
+		.sa_sigaction = timer_handler,
+		.sa_flags = SA_SIGINFO | SA_RESTART
+	};
+	__libc_sigaction(SIGTIMER, &sa, 0);
+	sigaddset(&sa.sa_mask, SIGTIMER);
+	__libc_sigprocmask(SIG_UNBLOCK, &sa.sa_mask, 0);
 }
 
 static void *start(void *arg)
@@ -58,6 +74,7 @@ static void *start(void *arg)
 
 int timer_create(clockid_t clk, struct sigevent *evp, timer_t *res)
 {
+	static pthread_once_t once = PTHREAD_ONCE_INIT;
 	pthread_t td;
 	pthread_attr_t attr;
 	int r;
@@ -80,6 +97,7 @@ int timer_create(clockid_t clk, struct sigevent *evp, timer_t *res)
 		*res = (void *)timerid;
 		break;
 	case SIGEV_THREAD:
+		pthread_once(&once, install_handler);
 		if (evp->sigev_notify_attributes)
 			attr = *evp->sigev_notify_attributes;
 		else
@@ -93,7 +111,7 @@ int timer_create(clockid_t clk, struct sigevent *evp, timer_t *res)
 			return -1;
 		}
 		ksev.sigev_value.sival_ptr = 0;
-		ksev.sigev_signo = SIGCANCEL;
+		ksev.sigev_signo = SIGTIMER;
 		ksev.sigev_notify = 4; /* SIGEV_THREAD_ID */
 		ksev.sigev_tid = td->tid;
 		r = syscall(SYS_timer_create, clk, &ksev, &timerid);