From: Oleg Nesterov Date: Wed, 30 Apr 2008 07:52:51 +0000 (-0700) Subject: signals: send_sig_info: don't take tasklist_lock X-Git-Tag: v2.6.26-rc1~291 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=08d2c30ce98d274137f12b0a9b9c74137455922c;p=linux-2.6 signals: send_sig_info: don't take tasklist_lock The comment in send_sig_info() is wrong, tasklist_lock can't help. The caller must ensure the task can't go away, otherwise ->sighand can be NULL even before we take the lock. p->sighand could be changed by exec(), but I can't imagine how it is possible to prevent exit(), but not exec(). Since the things seem to work, I assume all callers are correct. However, drm_vbl_send_signals() looks broken. block_all_signals() which is solely used by drm is definitely broken. Signed-off-by: Oleg Nesterov Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/signal.c b/kernel/signal.c index 13371d1735..17859f0d84 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1138,8 +1138,7 @@ static int kill_something_info(int sig, struct siginfo *info, int pid) */ /* - * These two are the most common entry points. They send a signal - * just to the specific thread. + * The caller must ensure the task can't exit. */ int send_sig_info(int sig, struct siginfo *info, struct task_struct *p) @@ -1154,17 +1153,9 @@ send_sig_info(int sig, struct siginfo *info, struct task_struct *p) if (!valid_signal(sig)) return -EINVAL; - /* - * We need the tasklist lock even for the specific - * thread case (when we don't need to follow the group - * lists) in order to avoid races with "p->sighand" - * going away or changing from under us. - */ - read_lock(&tasklist_lock); spin_lock_irqsave(&p->sighand->siglock, flags); ret = specific_send_sig_info(sig, info, p); spin_unlock_irqrestore(&p->sighand->siglock, flags); - read_unlock(&tasklist_lock); return ret; }