Messages in this thread | | | Date | Mon, 20 Aug 2012 17:41:54 +0200 | From | Oleg Nesterov <> | Subject | Re: lockdep trace from posix timers |
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On 08/20, Peter Zijlstra wrote: > > On Mon, 2012-08-20 at 17:05 +0200, Oleg Nesterov wrote: > > > > Yes, we can add the explicit argument to __task_work_run(), but it can > > check PF_EXITING instead, this looks simpler to me. > > I guess we could.. but I thought the explicit callback was simpler ;-)
I won't insist. The patch I sent uses PF_EXITING and the fake "struct callback_head* TWORK_EXITED", but this looks almost the same.
> > Note also your patch breaks fifo, but this is fixable. > > Why do you care about the order?
IMHO, this is just more natural.
For example. keyctl_session_to_parent() does _cancel only to protect from exploits doing keyctl(KEYCTL_SESSION_TO_PARENT) in an endless loop. It could simply do task_work_add(), but in this case we need fifo for correctness.
> Iterating a single linked queue in fifo > seems more expensive than useful.
Currently the list is fifo (we add to the last element), this is O(1).
But the list should be short, we can reverse it in _run() if we change task_work_add() to add to the head.
Oleg.
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