make sigprocmask(2) not take the kernel lock

Tests on a 4-core CPU show setjmp(3) run four times as fast under load.

discussed on tech@ some time ago, now by kettenis and guenther, ok deraadt

4 files changed, 20 insertions, 34 deletions

diff --git a/sys/compat/linux/linux_signal.c b/sys/compat/linux/linux_signal.c
index 22a03ae8dc9..b4d474f7205 100644
--- a/sys/compat/linux/linux_signal.c
+++ b/sys/compat/linux/linux_signal.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: linux_signal.c,v 1.17 2014/03/26 05:23:42 guenther Exp $	*/
+/*	$OpenBSD: linux_signal.c,v 1.18 2015/02/09 13:41:24 pelikan Exp $	*/
 /*	$NetBSD: linux_signal.c,v 1.10 1996/04/04 23:51:36 christos Exp $	*/
 
 /*
@@ -584,7 +584,6 @@ linux_sys_sigprocmask(p, v, retval)
 	linux_old_sigset_t ss;
 	sigset_t bs;
 	int error = 0;
-	int s;
 
 	*retval = 0;
 
@@ -604,19 +603,18 @@ linux_sys_sigprocmask(p, v, retval)
 
 	linux_old_to_bsd_sigset(&ss, &bs);
 
-	s = splhigh();
-
+	bs &= ~sigcantmask;
 	switch (SCARG(uap, how)) {
 	case LINUX_SIG_BLOCK:
-		p->p_sigmask |= bs & ~sigcantmask;
+		atomic_setbits_int(&p->p_sigmask, bs);
 		break;
 
 	case LINUX_SIG_UNBLOCK:
-		p->p_sigmask &= ~bs;
+		atomic_clearbits_int(&p->p_sigmask, bs);
 		break;
 
 	case LINUX_SIG_SETMASK:
-		p->p_sigmask = bs & ~sigcantmask;
+		p->p_sigmask = bs;
 		break;
 
 	default:
@@ -624,8 +622,6 @@ linux_sys_sigprocmask(p, v, retval)
 		break;
 	}
 
-	splx(s);
-
 	return (error);
 }
 
@@ -644,7 +640,6 @@ linux_sys_rt_sigprocmask(p, v, retval)
 	linux_sigset_t ls;
 	sigset_t bs;
 	int error = 0;
-	int s;
 
 	if (SCARG(uap, sigsetsize) != sizeof(linux_sigset_t))
 		return (EINVAL);
@@ -667,19 +662,18 @@ linux_sys_rt_sigprocmask(p, v, retval)
 
 	linux_to_bsd_sigset(&ls, &bs);
 
-	s = splhigh();
-
+	bs &= ~sigcantmask;
 	switch (SCARG(uap, how)) {
 	case LINUX_SIG_BLOCK:
-		p->p_sigmask |= bs & ~sigcantmask;
+		atomic_setbits_int(&p->p_sigmask, bs);
 		break;
 
 	case LINUX_SIG_UNBLOCK:
-		p->p_sigmask &= ~bs;
+		atomic_clearbits_int(&p->p_sigmask, bs);
 		break;
 
 	case LINUX_SIG_SETMASK:
-		p->p_sigmask = bs & ~sigcantmask;
+		p->p_sigmask = bs;
 		break;
 
 	default:
@@ -687,8 +681,6 @@ linux_sys_rt_sigprocmask(p, v, retval)
 		break;
 	}
 
-	splx(s);
-
 	return (error);
 }
 
@@ -727,16 +719,13 @@ linux_sys_sigsetmask(p, v, retval)
 	} */ *uap = v;
 	linux_old_sigset_t mask;
 	sigset_t bsdsig;
-	int s;
 
 	bsd_to_linux_old_sigset(&p->p_sigmask, (linux_old_sigset_t *)retval);
 
 	mask = SCARG(uap, mask);
 	bsd_to_linux_old_sigset(&bsdsig, &mask);
 
-	s = splhigh();
 	p->p_sigmask = bsdsig & ~sigcantmask;
-	splx(s);
 
 	return (0);
 }
diff --git a/sys/kern/init_sysent.c b/sys/kern/init_sysent.c
index edcb7a510c4..ba8df68d0a4 100644
--- a/sys/kern/init_sysent.c
+++ b/sys/kern/init_sysent.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: init_sysent.c,v 1.162 2015/02/09 13:34:49 deraadt Exp $	*/
+/*	$OpenBSD: init_sysent.c,v 1.163 2015/02/09 13:41:24 pelikan Exp $	*/
 
 /*
  * System call switch table.
@@ -124,7 +124,7 @@ struct sysent sysent[] = {
 	    sys_sigaction },			/* 46 = sigaction */
 	{ 0, 0, SY_NOLOCK | 0,
 	    sys_getgid },			/* 47 = getgid */
-	{ 2, s(struct sys_sigprocmask_args), 0,
+	{ 2, s(struct sys_sigprocmask_args), SY_NOLOCK | 0,
 	    sys_sigprocmask },			/* 48 = sigprocmask */
 	{ 2, s(struct sys_getlogin_args), 0,
 	    sys_getlogin },			/* 49 = getlogin */
diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index dfbab676fd4..761502cb24e 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_sig.c,v 1.177 2014/12/19 05:59:21 tedu Exp $	*/
+/*	$OpenBSD: kern_sig.c,v 1.178 2015/02/09 13:41:24 pelikan Exp $	*/
 /*	$NetBSD: kern_sig.c,v 1.54 1996/04/22 01:38:32 christos Exp $	*/
 
 /*
@@ -439,28 +439,25 @@ sys_sigprocmask(struct proc *p, void *v, register_t *retval)
 		syscallarg(sigset_t) mask;
 	} */ *uap = v;
 	int error = 0;
-	int s;
 	sigset_t mask;
 
 	*retval = p->p_sigmask;
-	mask = SCARG(uap, mask);
-	s = splhigh();
+	mask = SCARG(uap, mask) &~ sigcantmask;
 
 	switch (SCARG(uap, how)) {
 	case SIG_BLOCK:
-		p->p_sigmask |= mask &~ sigcantmask;
+		atomic_setbits_int(&p->p_sigmask, mask);
 		break;
 	case SIG_UNBLOCK:
-		p->p_sigmask &= ~mask;
+		atomic_clearbits_int(&p->p_sigmask, mask);
 		break;
 	case SIG_SETMASK:
-		p->p_sigmask = mask &~ sigcantmask;
+		p->p_sigmask = mask;
 		break;
 	default:
 		error = EINVAL;
 		break;
 	}
-	splx(s);
 	return (error);
 }
 
@@ -754,7 +751,7 @@ trapsignal(struct proc *p, int signum, u_long trapno, int code,
 		p->p_ru.ru_nsignals++;
 		(*pr->ps_emul->e_sendsig)(ps->ps_sigact[signum], signum,
 		    p->p_sigmask, trapno, code, sigval);
-		p->p_sigmask |= ps->ps_catchmask[signum];
+		atomic_setbits_int(&p->p_sigmask, ps->ps_catchmask[signum]);
 		if ((ps->ps_sigreset & mask) != 0) {
 			ps->ps_sigcatch &= ~mask;
 			if (signum != SIGCONT && sigprop[signum] & SA_IGNORE)
@@ -1378,7 +1375,7 @@ postsig(int signum)
 		} else {
 			returnmask = p->p_sigmask;
 		}
-		p->p_sigmask |= ps->ps_catchmask[signum];
+		atomic_setbits_int(&p->p_sigmask, ps->ps_catchmask[signum]);
 		if ((ps->ps_sigreset & mask) != 0) {
 			ps->ps_sigcatch &= ~mask;
 			if (signum != SIGCONT && sigprop[signum] & SA_IGNORE)
diff --git a/sys/kern/syscalls.master b/sys/kern/syscalls.master
index f981e71ed32..59e4f8e084f 100644
--- a/sys/kern/syscalls.master
+++ b/sys/kern/syscalls.master
@@ -1,4 +1,4 @@
-;	$OpenBSD: syscalls.master,v 1.150 2015/02/09 13:34:19 deraadt Exp $
+;	$OpenBSD: syscalls.master,v 1.151 2015/02/09 13:41:24 pelikan Exp $
 ;	$NetBSD: syscalls.master,v 1.32 1996/04/23 10:24:21 mycroft Exp $
 
 ;	@(#)syscalls.master	8.2 (Berkeley) 1/13/94
@@ -125,7 +125,7 @@
 			    const struct sigaction *nsa, \
 			    struct sigaction *osa); }
 47	STD NOLOCK	{ gid_t sys_getgid(void); }
-48	STD		{ int sys_sigprocmask(int how, sigset_t mask); }
+48	STD NOLOCK	{ int sys_sigprocmask(int how, sigset_t mask); }
 49	STD		{ int sys_getlogin(char *namebuf, u_int namelen); }
 50	STD		{ int sys_setlogin(const char *namebuf); }
 #ifdef ACCOUNTING