The patch titled
signals: send_sig_info: don't take tasklist_lock
has been removed from the -mm tree. Its filename was
signals-send_sig_info-dont-take-tasklist_lock.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: signals: send_sig_info: don't take tasklist_lock
From: Oleg Nesterov <oleg@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Roland McGrath <roland@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/signal.c | 11 +----------
1 file changed, 1 insertion(+), 10 deletions(-)
diff -puN kernel/signal.c~signals-send_sig_info-dont-take-tasklist_lock kernel/signal.c
--- a/kernel/signal.c~signals-send_sig_info-dont-take-tasklist_lock
+++ a/kernel/signal.c
@@ -1138,8 +1138,7 @@ static int kill_something_info(int sig,
*/
/*
- * 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 *i
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;
}
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
posix-timers-bug-10460-discard-the-pending-signal-when-the-timer-is-destroyed.patch
workqueue-remove-redundant-function-invocation.patch
put_pid-make-sure-we-dont-free-the-live-pid.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
