From 10ab825bdef8df510f99c703a5a2d9b13a4e31a5 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 9 May 2007 02:34:37 -0700 Subject: change kernel threads to ignore signals instead of blocking them Currently kernel threads use sigprocmask(SIG_BLOCK) to protect against signals. This doesn't prevent the signal delivery, this only blocks signal_wake_up(). Every "killall -33 kthreadd" means a "struct siginfo" leak. Change kthreadd_setup() to set all handlers to SIG_IGN instead of blocking them (make a new helper ignore_signals() for that). If the kernel thread needs some signal, it should use allow_signal() anyway, and in that case it should not use CLONE_SIGHAND. Note that we can't change daemonize() (should die!) in the same way, because it can be used along with CLONE_SIGHAND. This means that allow_signal() still should unblock the signal to work correctly with daemonize()ed threads. However, disallow_signal() doesn't block the signal any longer but ignores it. NOTE: with or without this patch the kernel threads are not protected from handle_stop_signal(), this seems harmless, but not good. Signed-off-by: Oleg Nesterov Acked-by: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/kthread.c | 17 +++-------------- 1 file changed, 3 insertions(+), 14 deletions(-) (limited to 'kernel/kthread.c') diff --git a/kernel/kthread.c b/kernel/kthread.c index 0eb0070a3c57..df8a8e8f6ca4 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -215,24 +215,13 @@ EXPORT_SYMBOL(kthread_stop); static __init void kthreadd_setup(void) { struct task_struct *tsk = current; - struct k_sigaction sa; - sigset_t blocked; set_task_comm(tsk, "kthreadd"); - /* Block and flush all signals */ - sigfillset(&blocked); - sigprocmask(SIG_BLOCK, &blocked, NULL); - flush_signals(tsk); + ignore_signals(tsk); - /* SIG_IGN makes children autoreap: see do_notify_parent(). */ - sa.sa.sa_handler = SIG_IGN; - sa.sa.sa_flags = 0; - siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD)); - do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0); - - set_user_nice(current, -5); - set_cpus_allowed(current, CPU_MASK_ALL); + set_user_nice(tsk, -5); + set_cpus_allowed(tsk, CPU_MASK_ALL); } int kthreadd(void *unused) -- cgit v1.2.3