On 01/13, Peter Zijlstra wrote: > > On Mon, 2008-01-07 at 20:49 +0300, Oleg Nesterov wrote: > > > 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); > > > > seems to work. What do you think? > > I've been pondering this for a while, and some days I really like it, > some days I don't. > > The problem I have with it is that it becomes very easy to falsely > annotate problems away - its a very powerful annotation.
Also, I don't like the overloading of ->trylock, this is really hackish. > I think I'll do wake_up_nested() for now and keep this around. Agreed. Perhaps it is a bit easier to use spin_lock_nested() + __wake_up_common() directly (we have a lot of wake_up_xxx helpers), but this is up to you. Offtopic question. Why do we have so many lockdep stuff in timer.c and hrtimer.c ? We never lock 2 bases at the same time, except in migrate_timers(). We can kill double_spin_lock() and base_lock_keys[] and just use spin_lock_nested in migrate_timers(), no? Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/