linux-kernel - Re: [PATCH] wait: don't wake up freezable wait by freezing fake signal

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Message-ID: <20230925100814.GA31921@noisy.programming.kicks-ass.net>
Date:   Mon, 25 Sep 2023 12:08:14 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ming Qian <ming.qian@....com>
Cc:     mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com, eagle.zhou@....com,
        tao.jiang_2@....com, linux-imx@....com,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] wait: don't wake up freezable wait by freezing fake
 signal

On Tue, Aug 22, 2023 at 03:45:47PM +0800, Ming Qian wrote:
> kernel may try to wake up task with fake signal when freezing task,
> if the task is waiting event using wait_event_freezable,
> it's better to freeze the wait, instead of breaking it.
> 
> otherwise the caller may need to retry the wait,
> maybe like below code:
> 
> 	if (rc == -ERESTARTSYS && freezing(current)) {
> 		clear_thread_flag(TIF_SIGPENDING);
> 		goto again;
> 	}

I'm not sure I get it -- is there an actual problem, or are you trying
to optimize something?