Messages in this thread | | | Date | Mon, 7 Jan 2008 20:49:08 +0300 | From | Oleg Nesterov <> | Subject | Re: 2.6.24-rc6: possible recursive locking detected |
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On 01/07, Oleg Nesterov wrote: > > Consider this "just for illustration" patch, > > --- t/kernel/lockdep.c 2007-11-09 12:57:31.000000000 +0300 > +++ t/kernel/lockdep.c 2008-01-07 19:43:50.000000000 +0300 > @@ -1266,10 +1266,13 @@ check_deadlock(struct task_struct *curr, > struct held_lock *prev; > int i; > > - for (i = 0; i < curr->lockdep_depth; i++) { > + for (i = curr->lockdep_depth; --i >= 0; ) { > prev = curr->held_locks + i; > if (prev->class != next->class) > continue; > + > + if (prev->trylock == -1) > + return 2; > /* > * Allow read-after-read recursion of the same > * lock class (i.e. read_lock(lock)+read_lock(lock)): > ------------------------------------------------------------------------- > > Now, > > // trylock == -1 > #define spin_mark_nested(l) \ > lock_acquire(&(l)->dep_map, 0, -1, 0, 2, _THIS_IP_) > #define spin_unmark_nested(l) \ > lock_release(&(l)->dep_map, 1, _THIS_IP_) > > and ep_poll_safewake() can do: > > /* Do really wake up now */ > spin_mark_nested(&wq->lock); > wake_up(wq); > spin_unmark_nested(&wq->lock);
I tested the patch above with the following code,
wait_queue_head_t w1, w2, w3;
init_waitqueue_head(&w1); init_waitqueue_head(&w2); init_waitqueue_head(&w3);
local_irq_disable(); spin_lock(&w1.lock);
spin_mark_nested(&w2.lock); spin_lock(&w2.lock);
spin_mark_nested(&w3.lock); wake_up(&w3); spin_unmark_nested(&w3.lock);
spin_unlock(&w2.lock); spin_unmark_nested(&w2.lock);
spin_unlock(&w1.lock); local_irq_enable();
seems to work. What do you think?
Oleg.
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