Re: [PATCH 2/3] context_tracking: Inherit TIF_NOHZ through forks instead of context switches

From: Rik van Riel
Date: Thu Apr 02 2015 - 14:07:53 EST

On 04/02/2015 01:39 PM, Frederic Weisbecker wrote:
> TIF_NOHZ is used by context_tracking to force syscall slow-path on every
> task in order to track userspace roundtrips. As such, it must be set on
> all running tasks.
> It's currently explicitly inherited through context switches. There is
> no need to do it on this fast-path though. The flag could be simply
> set once for all on all tasks, whether they are running or not.
> Lets do this by setting the flag to init task on early boot and let it
> propagate through fork inheritance.
> Suggested-by: Oleg Nesterov <oleg@xxxxxxxxxx>
> Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxx>
> Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Dave Jones <davej@xxxxxxxxxx>
> Cc: Oleg Nesterov <oleg@xxxxxxxxxx>

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

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