From b82c32872db20667d6ee8e2ea1e7bdec791bdcc7 Mon Sep 17 00:00:00 2001 From: Anton Vorontsov Date: Thu, 5 Apr 2012 14:25:05 -0700 Subject: [PATCH] sysrq: use SEND_SIG_FORCED instead of force_sig() Change send_sig_all() to use do_send_sig_info(SEND_SIG_FORCED) instead of force_sig(SIGKILL). With the recent changes we do not need force_ to kill the CLONE_NEWPID tasks. And this is more correct. force_sig() can race with the exiting thread, while do_send_sig_info(group => true) kill the whole process. Some more notes from Oleg Nesterov: > Just one note. This change makes no difference for sysrq_handle_kill(). > But it obviously changes the behaviour sysrq_handle_term(). I think > this is fine, if you want to really kill the task which blocks/ignores > SIGTERM you can use sysrq_handle_kill(). > > Even ignoring the reasons why force_sig() is simply wrong here, > force_sig(SIGTERM) looks strange. The task won't be killed if it has > a handler, but SIG_IGN can't help. However if it has the handler > but blocks SIGTERM temporary (this is very common) it will be killed. Also, > force_sig() can't kill the process if the main thread has already > exited. IOW, it is trivial to create the process which can't be > killed by sysrq. So, this patch fixes the issue. Suggested-by: Oleg Nesterov Acked-by: Greg Kroah-Hartman Acked-by: Oleg Nesterov Signed-off-by: Anton Vorontsov Cc: Alan Cox Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/tty/sysrq.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index 136e86faa1e1..05728894a88c 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -327,7 +327,7 @@ static void send_sig_all(int sig) if (is_global_init(p)) continue; - force_sig(sig, p); + do_send_sig_info(sig, SEND_SIG_FORCED, p, true); } read_unlock(&tasklist_lock); }