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Date:   Thu, 28 Apr 2022 11:08:36 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Jens Axboe <axboe@kernel.dk>
Cc:     LKML <linux-kernel@vger.kernel.org>, tglx@linutronix.de
Subject: Re: [PATCH] task_work: allow TWA_SIGNAL without a rescheduling IPI
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References: <543452ca-f82e-4f00-cd51-88bb9723a975@kernel.dk>
 <33a6de15-f487-b12b-8ffe-af978ebb03c3@kernel.dk>
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On Mon, Apr 25, 2022 at 07:52:31PM -0600, Jens Axboe wrote:
> On 4/22/22 8:34 AM, Jens Axboe wrote:
> > Some use cases don't always need an IPI when sending a TWA_SIGNAL
> > notification. Add TWA_SIGNAL_NO_IPI, which is just like TWA_SIGNAL,
> > except it doesn't send an IPI to the target task. It merely sets
> > TIF_NOTIFY_SIGNAL and wakes up the task.

Could you perphaps elaborate on those use-cases? How do they guarantee
the task_work is ran before userspace?