linux-kernel - Re: [PATCH v2 00/14] Introducing TIF_NOTIFY

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Message-ID: <20240615014521.GR8774@noisy.programming.kicks-ass.net>
Date: Sat, 15 Jun 2024 03:45:21 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Vincent Guittot <vincent.guittot@...aro.org>
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Subject: Re: [PATCH v2 00/14] Introducing TIF_NOTIFY_IPI flag

On Sat, Jun 15, 2024 at 03:28:14AM +0200, Peter Zijlstra wrote:
> On Fri, Jun 14, 2024 at 12:48:37PM +0200, Vincent Guittot wrote:

> > The main problem is that need_resched becomes somewhat meaningless
> > because it doesn't  only mean "I need to resched a task" and we have
> > to add more tests around even for those not using polling
> 
> True, however we already had some of that by having the wakeup list,
> that made nr_running less 'reliable'.

Doesn't using !idle_cpu() instead of need_resched() in those balance
paths already do the right thing?

Checking need_resched() as an indicator of it getting work is already a
bit an assumption.

Also, Ingo, idle_cpu() and friends don't really belong in syscalls.c...