linux-kernel - Re: [PATCH v1] net/dev.c : Remove redundant state settings after waking up

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Message-ID: <20230110163043.069c9aa4@kernel.org>
Date:   Tue, 10 Jan 2023 16:30:43 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     李哲 <sensor1010@....com>,
        Wei Wang <weiwan@...gle.com>, davem@...emloft.net,
        pabeni@...hat.com, bigeasy@...utronix.de, imagedong@...cent.com,
        kuniyu@...zon.com, petrm@...dia.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] net/dev.c : Remove redundant state settings after
 waking up

On Tue, 10 Jan 2023 10:29:20 +0100 Eric Dumazet wrote:
> > the task status has been set to TASK_RUNNING in shcedule(),
> > no need to set again here  
> 
> Changelog is rather confusing, this does not match the patch, which
> removes one set_current_state(TASK_INTERRUPTIBLE);
> 
> TASK_INTERRUPTIBLE != TASK_RUNNING
> 
> Patch itself looks okay (but has nothing to do with thread state after
> schedule()),
> you should have CC Wei Wang because she
> authored commit cb038357937e net: fix race between napi kthread mode
> and busy poll

AFAIU this is the semi-idiomatic way of handling wait loops.
It's not schedule() that may set the task state to TASK_RUNNING,
it's whoever wakes the process and makes the "wait condition" true.
In this case - test_bit(NAPI_STATE_SCHED, &napi->state)

I vote to not futz with this logic.