From f63ee72e0fb82e504a0489490babc7612c7cd6c2 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 28 Mar 2006 16:11:13 -0800 Subject: [PATCH] introduce lock_task_sighand() helper Add lock_task_sighand() helper and converts group_send_sig_info() to use it. Hopefully we will have more users soon. This patch also removes '!sighand->count' and '!p->usage' checks, I think they both are bogus, racy and unneeded (but probably it makes sense to restore them as BUG_ON()s). ->sighand is cleared and it's ->count is decremented in release_task() with sighand->siglock held, so it is a bug to have '!p->usage || !->count' after we already locked and verified it is the same. On the other hand, an already dead task without ->sighand can have a non-zero ->usage due to ptrace, for example. If we read the stale value of ->sighand we must see the change after spin_lock(), because that change was done while holding that same old ->sighand.siglock. Signed-off-by: Oleg Nesterov Cc: "Eric W. Biederman" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sched.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/linux') diff --git a/include/linux/sched.h b/include/linux/sched.h index bbcfc873bd9..ca1fd31aae9 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1225,6 +1225,15 @@ static inline void task_unlock(struct task_struct *p) spin_unlock(&p->alloc_lock); } +extern struct sighand_struct *lock_task_sighand(struct task_struct *tsk, + unsigned long *flags); + +static inline void unlock_task_sighand(struct task_struct *tsk, + unsigned long *flags) +{ + spin_unlock_irqrestore(&tsk->sighand->siglock, *flags); +} + #ifndef __HAVE_THREAD_FUNCTIONS #define task_thread_info(task) (task)->thread_info -- cgit v1.2.3