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authorOleg Nesterov <oleg@tv-sign.ru>2007-05-09 02:34:37 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-09 12:30:53 -0700
commit10ab825bdef8df510f99c703a5a2d9b13a4e31a5 (patch)
treee4db81f26c03ba5a5bff43ed44646a4ed4509d67
parent5de18d169739293e27e0cf9acfc75a2d2f4aa572 (diff)
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 <oleg@tv-sign.ru> Acked-by: "Eric W. Biederman" <ebiederm@xmission.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/sched.h1
-rw-r--r--kernel/exit.c2
-rw-r--r--kernel/kthread.c17
-rw-r--r--kernel/signal.c10
4 files changed, 15 insertions, 15 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 3d95c480f58..28000b1658f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1317,6 +1317,7 @@ extern int in_egroup_p(gid_t);
extern void proc_caches_init(void);
extern void flush_signals(struct task_struct *);
+extern void ignore_signals(struct task_struct *);
extern void flush_signal_handlers(struct task_struct *, int force_default);
extern int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info);
diff --git a/kernel/exit.c b/kernel/exit.c
index bc982cd7274..b0c6f0c3a2d 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -347,7 +347,7 @@ int disallow_signal(int sig)
return -EINVAL;
spin_lock_irq(&current->sighand->siglock);
- sigaddset(&current->blocked, sig);
+ current->sighand->action[(sig)-1].sa.sa_handler = SIG_IGN;
recalc_sigpending();
spin_unlock_irq(&current->sighand->siglock);
return 0;
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 0eb0070a3c5..df8a8e8f6ca 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)
diff --git a/kernel/signal.c b/kernel/signal.c
index 23ae6d62fc4..2ac3a668d9d 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -209,6 +209,16 @@ void flush_signals(struct task_struct *t)
spin_unlock_irqrestore(&t->sighand->siglock, flags);
}
+void ignore_signals(struct task_struct *t)
+{
+ int i;
+
+ for (i = 0; i < _NSIG; ++i)
+ t->sighand->action[i].sa.sa_handler = SIG_IGN;
+
+ flush_signals(t);
+}
+
/*
* Flush all handlers for a task.
*/