runtime: fix running under nohup

There are two ways nohup(1) might be implemented:
it might mask away the signal, or it might set the handler
to SIG_IGN, both of which are inherited across fork+exec.
So two fixes:

* Make sure to preserve the inherited signal mask at
minit instead of clearing it.

* If the SIGHUP handler is SIG_IGN, leave it that way.

Fixes #4491.

R=golang-dev, mikioh.mikioh, iant
CC=golang-dev
https://golang.org/cl/7308102

src/pkg/runtime/os_darwin.h

@@ -4,6 +4,7 @@
 
 #define SIG_DFL ((void*)0)
 #define SIG_IGN ((void*)1)
+#define SIGHUP 1
 
 int32	runtime·bsdthread_create(void*, M*, G*, void(*)(void));
 int32	runtime·bsdthread_register(void);

src/pkg/runtime/os_freebsd.h

@@ -1,5 +1,6 @@
 #define SIG_DFL ((void*)0)
 #define SIG_IGN ((void*)1)
+#define SIGHUP 1
 
 int32	runtime·thr_new(ThrParam*, int32);
 void	runtime·sighandler(int32 sig, Siginfo *info, void *context, G *gp);

src/pkg/runtime/os_linux.h

@@ -4,6 +4,7 @@
 
 #define SIG_DFL ((void*)0)
 #define SIG_IGN ((void*)1)
+#define SIGHUP 1
 
 // Linux-specific system calls
 int32	runtime·futex(uint32*, int32, uint32, Timespec*, uint32*, uint32);

src/pkg/runtime/os_netbsd.h

@@ -4,6 +4,7 @@
 
 #define SIG_DFL ((void*)0)
 #define SIG_IGN ((void*)1)
+#define SIGHUP 1
 
 #define SIG_BLOCK 1
 #define SIG_UNBLOCK 2

src/pkg/runtime/os_openbsd.h

@@ -4,6 +4,7 @@
 
 #define SIG_DFL ((void*)0)
 #define SIG_IGN ((void*)1)
+#define SIGHUP 1
 
 #define SIG_BLOCK 1
 #define SIG_UNBLOCK 2

src/pkg/runtime/runtime.h

@@ -290,6 +290,7 @@ struct	M
 	GCStats	gcstats;
 	bool	racecall;
 	void*	racepc;
+	void*	sigset;
 	uint32	moreframesize_minalloc;
 
 	uintptr	settype_buf[1024];

src/pkg/runtime/signal_darwin_386.c

@@ -133,6 +133,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(*(void**)sa.__sigaction_u == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_SIGINFO|SA_ONSTACK;
 	if(restart)

src/pkg/runtime/signal_darwin_amd64.c

@@ -143,6 +143,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(*(void**)sa.__sigaction_u == SIG_IGN)
+			return;
+	}
+		
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_SIGINFO|SA_ONSTACK;
 	if(restart)

src/pkg/runtime/signal_freebsd_386.c

@@ -128,6 +128,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(sa.__sigaction_u.__sa_sigaction == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_SIGINFO|SA_ONSTACK;
 	if(restart)

src/pkg/runtime/signal_freebsd_amd64.c

@@ -136,6 +136,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(sa.__sigaction_u.__sa_sigaction == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_SIGINFO|SA_ONSTACK;
 	if(restart)

src/pkg/runtime/signal_freebsd_arm.c

@@ -151,6 +151,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(sa.__sigaction_u.__sa_sigaction == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_SIGINFO|SA_ONSTACK;
 	if(restart)

src/pkg/runtime/signal_linux_386.c

@@ -124,6 +124,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(sa.k_sa_handler == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_ONSTACK | SA_SIGINFO | SA_RESTORER;
 	if(restart)

src/pkg/runtime/signal_linux_amd64.c

@@ -134,6 +134,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(sa.sa_handler == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_ONSTACK | SA_SIGINFO | SA_RESTORER;
 	if(restart)

src/pkg/runtime/signal_linux_arm.c

@@ -140,6 +140,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(sa.sa_handler == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_ONSTACK | SA_SIGINFO | SA_RESTORER;
 	if(restart)

src/pkg/runtime/signal_netbsd_386.c

@@ -128,6 +128,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(sa._sa_u._sa_sigaction == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_SIGINFO|SA_ONSTACK;
 	if(restart)

src/pkg/runtime/signal_netbsd_amd64.c

@@ -135,6 +135,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(sa._sa_u._sa_sigaction == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_SIGINFO|SA_ONSTACK;
 	if(restart)

src/pkg/runtime/signal_netbsd_arm.c

@@ -157,6 +157,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(sa._sa_u._sa_sigaction == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_SIGINFO|SA_ONSTACK;
 	if(restart)

src/pkg/runtime/signal_openbsd_386.c

@@ -124,6 +124,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(sa.__sigaction_u.__sa_sigaction == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_SIGINFO|SA_ONSTACK;
 	if(restart)

src/pkg/runtime/signal_openbsd_amd64.c

@@ -133,6 +133,15 @@ runtime·setsig(int32 i, void (*fn)(int32, Siginfo*, void*, G*), bool restart)
 {
 	Sigaction sa;
 
+	// If SIGHUP handler is SIG_IGN, assume running
+	// under nohup and do not set explicit handler.
+	if(i == SIGHUP) {
+		runtime·memclr((byte*)&sa, sizeof sa);
+		runtime·sigaction(i, nil, &sa);
+		if(sa.__sigaction_u.__sa_sigaction == SIG_IGN)
+			return;
+	}
+
 	runtime·memclr((byte*)&sa, sizeof sa);
 	sa.sa_flags = SA_SIGINFO|SA_ONSTACK;
 	if(restart)

src/pkg/runtime/thread_darwin.c

@@ -10,7 +10,6 @@
 extern SigTab runtime·sigtab[];
 
 static Sigset sigset_all = ~(Sigset)0;
-static Sigset sigset_none;
 static Sigset sigset_prof = 1<<(SIGPROF-1);
 
 static void
@@ -99,6 +98,8 @@ runtime·newosproc(M *mp, G *gp, void *stk, void (*fn)(void))
 	}
 
 	runtime·sigprocmask(SIG_SETMASK, &sigset_all, &oset);
+	mp->sigset = runtime·mal(sizeof(Sigset));
+	*(Sigset*)mp->sigset = oset;
 	errno = runtime·bsdthread_create(stk, mp, gp, fn);
 	runtime·sigprocmask(SIG_SETMASK, &oset, nil);
 
@@ -116,10 +117,9 @@ runtime·minit(void)
 	m->gsignal = runtime·malg(32*1024);	// OS X wants >=8K, Linux >=2K
 	runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
 
-	if(m->profilehz > 0)
-		runtime·sigprocmask(SIG_SETMASK, &sigset_none, nil);
-	else
-		runtime·sigprocmask(SIG_SETMASK, &sigset_prof, nil);
+	if(m->sigset != nil)
+		runtime·sigprocmask(SIG_SETMASK, m->sigset, nil);
+	runtime·setprof(m->profilehz > 0);
 }
 
 // Mach IPC, to get at semaphores

src/pkg/runtime/thread_freebsd.c

@@ -14,7 +14,6 @@ extern int32 runtime·sys_umtx_op(uint32*, int32, uint32, void*, void*);
 #define	HW_NCPU	3
 
 static Sigset sigset_all = { ~(uint32)0, ~(uint32)0, ~(uint32)0, ~(uint32)0, };
-static Sigset sigset_none = { 0, 0, 0, 0, };
 
 static int32
 getncpu(void)
@@ -91,6 +90,8 @@ runtime·newosproc(M *mp, G *gp, void *stk, void (*fn)(void))
 	}
 
 	runtime·sigprocmask(&sigset_all, &oset);
+	mp->sigset = runtime·mal(sizeof(Sigset));
+	*(Sigset*)mp->sigset = oset;
 	runtime·memclr((byte*)&param, sizeof param);
 
 	param.start_func = runtime·thr_start;
@@ -127,7 +128,8 @@ runtime·minit(void)
 	// Initialize signal handling
 	m->gsignal = runtime·malg(32*1024);
 	runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
-	runtime·sigprocmask(&sigset_none, nil);
+	if(m->sigset != nil)
+		runtime·sigprocmask(m->sigset, nil);
 }
 
 void

src/pkg/runtime/thread_linux.c

@@ -14,7 +14,6 @@ int32 runtime·close(int32);
 int32 runtime·read(int32, void*, int32);
 
 static Sigset sigset_all = { ~(uint32)0, ~(uint32)0 };
-static Sigset sigset_none;
 
 // Linux futex.
 //
@@ -149,6 +148,8 @@ runtime·newosproc(M *mp, G *gp, void *stk, void (*fn)(void))
 	// Disable signals during clone, so that the new thread starts
 	// with signals disabled.  It will enable them in minit.
 	runtime·rtsigprocmask(SIG_SETMASK, &sigset_all, &oset, sizeof oset);
+	mp->sigset = runtime·mal(sizeof(Sigset));
+	*(Sigset*)mp->sigset = oset;
 	ret = runtime·clone(flags, stk, mp, gp, fn);
 	runtime·rtsigprocmask(SIG_SETMASK, &oset, nil, sizeof oset);
 
@@ -177,7 +178,8 @@ runtime·minit(void)
 	// Initialize signal handling.
 	m->gsignal = runtime·malg(32*1024);	// OS X wants >=8K, Linux >=2K
 	runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
-	runtime·rtsigprocmask(SIG_SETMASK, &sigset_none, nil, sizeof sigset_none);
+	if(m->sigset != nil)
+		runtime·rtsigprocmask(SIG_SETMASK, m->sigset, nil, sizeof *m->sigset);
 }
 
 void

src/pkg/runtime/thread_netbsd.c

@@ -21,7 +21,6 @@ enum
 extern SigTab runtime·sigtab[];
 
 static Sigset sigset_all = { ~(uint32)0, ~(uint32)0, ~(uint32)0, ~(uint32)0, };
-static Sigset sigset_none;
 
 extern void runtime·getcontext(UcontextT *context);
 extern int32 runtime·lwp_create(UcontextT *context, uintptr flags, void *lwpid);
@@ -164,6 +163,9 @@ runtime·newosproc(M *mp, G *gp, void *stk, void (*fn)(void))
 	uc.uc_link = nil;
 	uc.uc_sigmask = sigset_all;
 
+	mp->sigset = runtime·mal(sizeof(Sigset));
+	runtime·sigprocmask(SIG_SETMASK, nil, mp->sigset);
+
 	runtime·lwp_mcontext_init(&uc.uc_mcontext, stk, mp, gp, fn);
 
 	ret = runtime·lwp_create(&uc, 0, &mp->procid);
@@ -195,7 +197,8 @@ runtime·minit(void)
 	// Initialize signal handling
 	m->gsignal = runtime·malg(32*1024);
 	runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
-	runtime·sigprocmask(SIG_SETMASK, &sigset_none, nil);
+	if(m->sigset != nil)
+		runtime·sigprocmask(SIG_SETMASK, m->sigset, nil);
 }
 
 void

src/pkg/runtime/thread_openbsd.c

@@ -21,7 +21,6 @@ enum
 extern SigTab runtime·sigtab[];
 
 static Sigset sigset_all = ~(Sigset)0;
-static Sigset sigset_none;
 
 extern int64 runtime·tfork(void *param, uintptr psize, M *mp, G *gp, void (*fn)(void));
 extern int32 runtime·thrsleep(void *ident, int32 clock_id, void *tsp, void *lock, const int32 *abort);
@@ -142,6 +141,8 @@ runtime·newosproc(M *mp, G *gp, void *stk, void (*fn)(void))
 	param.tf_stack = stk;
 
 	oset = runtime·sigprocmask(SIG_SETMASK, sigset_all);
+	mp->sigset = runtime·mal(sizeof(Sigset));
+	*(Sigset*)mp->sigset = oset;
 	ret = runtime·tfork((byte*)&param, sizeof(param), mp, gp, fn);
 	runtime·sigprocmask(SIG_SETMASK, oset);
 
@@ -172,7 +173,8 @@ runtime·minit(void)
 	// Initialize signal handling
 	m->gsignal = runtime·malg(32*1024);
 	runtime·signalstack((byte*)m->gsignal->stackguard - StackGuard, 32*1024);
-	runtime·sigprocmask(SIG_SETMASK, sigset_none);
+	if(m->sigset != nil)
+		runtime·sigprocmask(SIG_SETMASK, m->sigset, nil, sizeof *m->sigset);
 }
 
 void