Re: [patch] del_timer_sync scalability patch

From: Ingo Molnar
Date: Tue Mar 15 2005 - 04:32:04 EST

* Christoph Lameter <christoph@xxxxxxxxxxx> wrote:

> The following patch removes the magic in the timer_list structure
> (Andrew suggested that we may not need it anymore) and replaces it
> with two u8 variables that give us some additional state of the timer

The 'remove the magic' observation is not a 'backdoor' to introduce new
fields 'for free'. So please dont mix the two things into one patch.

> + u8 running; /* function is currently executing */
> + u8 shutdown; /* do not schedule this timer */

it may as well be cleaner to do the timer->base_running thing after all,
and to do this in __run_timers():

timer->base = NULL;
timer->base_running = base;

note that we cannot clear ->base_running in __run_timers() [we dont own
any access to the timer anymore, it may be kfree()d, etc.], so
del_timer_sync() has to make sure that the timer->base_running info is
not stale - it is a hint only. But it looks doable, and it should solve
the NUMA scalability problem.

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