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authorOleg Nesterov <oleg@tv-sign.ru>2008-04-30 07:52:51 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2008-04-30 15:29:35 (GMT)
commit08d2c30ce98d274137f12b0a9b9c74137455922c (patch)
treecc649fd249aef0c4d227406b17a1a75c9d327e50
parent3547ff3aefbe092ca35506c60c02e2d17a4f2199 (diff)
downloadlinux-08d2c30ce98d274137f12b0a9b9c74137455922c.tar.xz
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 <oleg@tv-sign.ru> Cc: Roland McGrath <roland@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/signal.c11
1 files changed, 1 insertions, 10 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index 13371d1..17859f0 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;
}