sigsuspend: proper behaviour

kernel-src/include/kernel/scheduler.h

@@ -59,8 +59,10 @@ typedef struct thread_t {
 		stack_t stack;
 		sigset_t mask;
 		sigset_t pending;
-		sigset_t urgent;
-		sigset_t waiting;
+		sigset_t urgent; // always handled before returning to userspace
+		sigset_t waiting; // for signal_wait
+		sigset_t oldmask; // for signal_suspend
+		bool suspending;
 		bool stopped;
 	} signals;
 } thread_t;

kernel-src/include/kernel/signal.h

@@ -158,6 +158,7 @@ void signal_changemask(struct thread_t *thread, int how, sigset_t *new, sigset_t
 void signal_signalproc(struct proc_t *proc, int signal);
 void signal_signalthread(struct thread_t *thread, int signal, bool urgent);
 void signal_pending(struct thread_t *, sigset_t *sigset);
+void signal_suspend(sigset_t *sigset);
 int signal_wait(sigset_t *sigset, timespec_t *timeout, siginfo_t *siginfo, int *signum);
 bool signal_check(struct thread_t *thread, context_t *context, bool syscall, uint64_t syscallret, uint64_t syscallerrno);
 extern int signal_defaultactions[NSIG];

kernel-src/sys/signal.c

@@ -139,6 +139,20 @@ void signal_pending(struct thread_t *thread, sigset_t *sigset) {
 	PROCESS_LEAVE(proc);
 }
 
+void signal_suspend(sigset_t *sigset) {
+	thread_t *thread = _cpu()->thread;
+	THREAD_ENTER(thread);
+
+	memcpy(&thread->signals.oldmask, &thread->signals.mask, sizeof(sigset_t));
+	memcpy(&thread->signals.mask, sigset, sizeof(sigset_t));
+	thread->signals.suspending = true;
+
+	THREAD_LEAVE(thread);
+
+	sched_preparesleep(true);
+	sched_yield();
+}
+
 int signal_wait(sigset_t *sigset, timespec_t *timeout, siginfo_t *siginfo, int *signum) {
 	thread_t *thread = _cpu()->thread;
 	PROCESS_ENTER(thread->proc);
@@ -531,7 +545,16 @@ bool signal_check(struct thread_t *thread, context_t *context, bool syscall, uin
 			memcpy(&sigframe.oldstack, &thread->signals.stack, sizeof(stack_t));
 			memset(&thread->signals.stack, 0, sizeof(stack_t));
 		}
-		memcpy(&sigframe.oldmask, &thread->signals.mask, sizeof(sigset_t));
+
+		if (thread->signals.suspending) {
+			// if we were waiting in signal_suspend, push the old mask into the return frame
+			// of the first signal and set it to not act this way the next check
+			memcpy(&sigframe.oldmask, &thread->signals.oldmask, sizeof(sigset_t));
+			thread->signals.suspending = false;
+		} else {
+			// else, just push the current mask
+			memcpy(&sigframe.oldmask, &thread->signals.mask, sizeof(sigset_t));
+		}
 		memcpy(&sigframe.context, context, sizeof(context_t));
 		memcpy(&sigframe.extracontext, &thread->extracontext, sizeof(extracontext_t));
 		// TODO siginfo

kernel-src/sys/syscalls/sigsuspend.c

@@ -8,18 +8,12 @@ syscallret_t syscall_sigsuspend(context_t *, sigset_t *umask) {
 	};
 
 	sigset_t mask;
-	sigset_t old;
 
 	ret.errno = usercopy_fromuser(&mask, umask, sizeof(sigset_t));
 	if (ret.errno)
 		return ret;
 
-	signal_changemask(_cpu()->thread, SIG_SETMASK, &mask, &old);
-
-	sched_preparesleep(true);
-	__assert(sched_yield() == SCHED_WAKEUP_REASON_INTERRUPTED);
-
-	signal_changemask(_cpu()->thread, SIG_SETMASK, &old, NULL);
+	signal_suspend(&mask);
 
 	ret.errno = EINTR;
 	return ret;