[PATCH] convert signal handling of NODEFER to act like other Unix boxes.

It has been reported that the way Linux handles NODEFER for signals is
not consistent with the way other Unix boxes handle it.  I've written a
program to test the behavior of how this flag affects signals and had
several reports from people who ran this on various Unix boxes,
confirming that Linux seems to be unique on the way this is handled.

The way NODEFER affects signals on other Unix boxes is as follows:

1) If NODEFER is set, other signals in sa_mask are still blocked.

2) If NODEFER is set and the signal is in sa_mask, then the signal is
still blocked. (Note: this is the behavior of all tested but Linux _and_
NetBSD 2.0 *).

The way NODEFER affects signals on Linux:

1) If NODEFER is set, other signals are _not_ blocked regardless of
sa_mask (Even NetBSD doesn't do this).

2) If NODEFER is set and the signal is in sa_mask, then the signal being
handled is not blocked.

The patch converts signal handling in all current Linux architectures to
the way most Unix boxes work.

Unix boxes that were tested:  DU4, AIX 5.2, Irix 6.5, NetBSD 2.0, SFU
3.5 on WinXP, AIX 5.3, Mac OSX, and of course Linux 2.6.13-rcX.

* NetBSD was the only other Unix to behave like Linux on point #2. The
main concern was brought up by point #1 which even NetBSD isn't like
Linux.  So with this patch, we leave NetBSD as the lonely one that
behaves differently here with #2.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 15 insertions, 18 deletions

diff --git a/arch/mips/kernel/irixsig.c b/arch/mips/kernel/irixsig.c
index 40244782a8e..4c114ae2179 100644
--- a/arch/mips/kernel/irixsig.c
+++ b/arch/mips/kernel/irixsig.c
@@ -155,13 +155,12 @@ static inline void handle_signal(unsigned long sig, siginfo_t *info,
 	else
 		setup_irix_frame(ka, regs, sig, oldset);
 
-	if (!(ka->sa.sa_flags & SA_NODEFER)) {
-		spin_lock_irq(&current->sighand->siglock);
-		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
+	spin_lock_irq(&current->sighand->siglock);
+	sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
+	if (!(ka->sa.sa_flags & SA_NODEFER))
 		sigaddset(&current->blocked,sig);
-		recalc_sigpending();
-		spin_unlock_irq(&current->sighand->siglock);
-	}
+	recalc_sigpending();
+	spin_unlock_irq(&current->sighand->siglock);
 }
 
 asmlinkage int do_irix_signal(sigset_t *oldset, struct pt_regs *regs)
diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index 65ee15396ff..0209c1dd142 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -425,13 +425,12 @@ static inline void handle_signal(unsigned long sig, siginfo_t *info,
 		setup_frame(ka, regs, sig, oldset);
 #endif
 
-	if (!(ka->sa.sa_flags & SA_NODEFER)) {
-		spin_lock_irq(&current->sighand->siglock);
-		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
+	spin_lock_irq(&current->sighand->siglock);
+	sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
+	if (!(ka->sa.sa_flags & SA_NODEFER))
 		sigaddset(&current->blocked,sig);
-		recalc_sigpending();
-		spin_unlock_irq(&current->sighand->siglock);
-	}
+	recalc_sigpending();
+	spin_unlock_irq(&current->sighand->siglock);
 }
 
 extern int do_signal32(sigset_t *oldset, struct pt_regs *regs);
diff --git a/arch/mips/kernel/signal32.c b/arch/mips/kernel/signal32.c
index c1a69cf232f..f6875f023a2 100644
--- a/arch/mips/kernel/signal32.c
+++ b/arch/mips/kernel/signal32.c
@@ -751,13 +751,12 @@ static inline void handle_signal(unsigned long sig, siginfo_t *info,
 	else
 		setup_frame(ka, regs, sig, oldset);
 
-	if (!(ka->sa.sa_flags & SA_NODEFER)) {
-		spin_lock_irq(&current->sighand->siglock);
-		sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
+	spin_lock_irq(&current->sighand->siglock);
+	sigorsets(&current->blocked,&current->blocked,&ka->sa.sa_mask);
+	if (!(ka->sa.sa_flags & SA_NODEFER))
 		sigaddset(&current->blocked,sig);
-		recalc_sigpending();
-		spin_unlock_irq(&current->sighand->siglock);
-	}
+	recalc_sigpending();
+	spin_unlock_irq(&current->sighand->siglock);
 }
 
 int do_signal32(sigset_t *oldset, struct pt_regs *regs)