Re: [PATCH v3 1/3] lockdep: Make LOCKDEP_CROSSRELEASE configs all part of PROVE_LOCKING

[Oleg Nesterov]

Peter, I am all confused and I am still trying to understand your email.
In particular, because I no longer understand the lockdep annotations in
workqueue.c, it turns out I forgot everything...

On 08/22, Peter Zijlstra wrote:
>
> I am however slightly puzzled by the need of flush_work() to take Q,
> what deadlock potential is there?

Do you really mean flush_work()? Or start_flush_work() ?

> It was added by Oleg in commit:
>
>   a67da70dc095 ("workqueues: lockdep annotations for flush_work()")

No, these annotations were moved later into start_flush, iiuc...

This

	lock_map_acquire(&work->lockdep_map);
	lock_map_release(&work->lockdep_map);

was added by another commit 0976dfc1d0cd80a4e9dfaf87bd8744612bde475a
"workqueue: Catch more locking problems with flush_work()", and at
first glance it is fine.

At the same time, I have a vague feeling that (perhaps) we can remove
these 2 annotations if we change process_one_work() and start_flush_work(),
not sure...

Oleg.