From 87245135d5057edd5a8037131f81eeffd76d4fef Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 17 Jun 2009 16:27:23 -0700 Subject: [PATCH] allow_signal: kill the bogus ->mm check, add a note about CLONE_SIGHAND allow_signal() checks ->mm == NULL. Not sure why. Perhaps to make sure current is the kernel thread. But this helper must not be used unless we are the kernel thread, kill this check. Also, document the fact that the CLONE_SIGHAND kthread must not use allow_signal(), unless the caller really wants to change the parent's ->sighand->action as well. Signed-off-by: Oleg Nesterov Acked-by: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/exit.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index b6c90b5ef509..533e5f85669a 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -375,9 +375,8 @@ static void set_special_pids(struct pid *pid) } /* - * Let kernel threads use this to say that they - * allow a certain signal (since daemonize() will - * have disabled all of them by default). + * Let kernel threads use this to say that they allow a certain signal. + * Must not be used if kthread was cloned with CLONE_SIGHAND. */ int allow_signal(int sig) { @@ -385,14 +384,14 @@ int allow_signal(int sig) return -EINVAL; spin_lock_irq(¤t->sighand->siglock); + /* This is only needed for daemonize()'ed kthreads */ sigdelset(¤t->blocked, sig); - if (!current->mm) { - /* Kernel threads handle their own signals. - Let the signal code know it'll be handled, so - that they don't get converted to SIGKILL or - just silently dropped */ - current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2; - } + /* + * Kernel threads handle their own signals. Let the signal code + * know it'll be handled, so that they don't get converted to + * SIGKILL or just silently dropped. + */ + current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2; recalc_sigpending(); spin_unlock_irq(¤t->sighand->siglock); return 0;