Messages in this thread Patch in this message | | | Date | Tue, 26 Jan 2010 19:16:41 +0100 | From | Oleg Nesterov <> | Subject | check_usage_backwards() && forwards? (Was: [2.6.33-rc5] starting emacs makes lockdep warning) |
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(add lockdep gurus)
Lockdep has found the real bug, but the output doesn't look right to me
On 01/26, KOSAKI Motohiro wrote: > > ========================================================= > [ INFO: possible irq lock inversion dependency detected ] > 2.6.33-rc5 #77 > --------------------------------------------------------- > emacs/1609 just changed the state of lock: > (&(&tty->ctrl_lock)->rlock){+.....}, at: [<ffffffff8127c648>] tty_fasync+0xe8/0x190 > but this lock took another, HARDIRQ-unsafe lock in the past: > (&(&sighand->siglock)->rlock){-.....}
"HARDIRQ-unsafe" and "this lock took another" looks wrong, afaics.
> ... key at: [<ffffffff81c054a4>] __key.46539+0x0/0x8 > ... acquired at: > [<ffffffff81089af6>] __lock_acquire+0x1056/0x15a0 > [<ffffffff8108a0df>] lock_acquire+0x9f/0x120 > [<ffffffff81423012>] _raw_spin_lock_irqsave+0x52/0x90 > [<ffffffff8127c1be>] __proc_set_tty+0x3e/0x150 > [<ffffffff8127e01d>] tty_open+0x51d/0x5e0
The stack-trace shows that this lock (ctrl_lock) was taken under ->siglock (which is hopefully irq-safe).
Typo in check_usage_backwards() ?
Oleg.
--- a/kernel/lockdep.c +++ b/kernel/lockdep.c @@ -2147,7 +2147,7 @@ check_usage_backwards(struct task_struct return ret; return print_irq_inversion_bug(curr, &root, target_entry, - this, 1, irqclass); + this, 0, irqclass); } void print_irqtrace_events(struct task_struct *curr)
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