linux-kernel - Re: [RT PATCH] locking/rwsem-rt: Remove might_sleep() in __up

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Message-ID: <20210426164229.mbrsrjpmmhp7ehna@halaneylaptop>
Date:   Mon, 26 Apr 2021 11:42:29 -0500
From:   Andrew Halaney <ahalaney@...hat.com>
To:     bigeasy@...utronix.de
Cc:     linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org,
        Chunyu Hu <chuhu@...hat.com>
Subject: Re: [RT PATCH] locking/rwsem-rt: Remove might_sleep() in __up_read()

On Tue, Apr 06, 2021 at 05:19:52PM -0500, Andrew Halaney wrote:
> There's no chance of sleeping here, the reader is giving up the
> lock and possibly waking up the writer who is waiting on it.
> 
> Reported-by: Chunyu Hu <chuhu@...hat.com>
> Signed-off-by: Andrew Halaney <ahalaney@...hat.com>
> ---
> Hello,
> 
> I ran into a warning caused by this, and I think the warning is
> incorrect. Please let me know if I'm wrong!
> I'm working off of linux-5.12.y-rt, but this applies cleanly to older
> stable branches as well.
> 
> Thanks,
> Andrew
> 
>  kernel/locking/rwsem-rt.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/kernel/locking/rwsem-rt.c b/kernel/locking/rwsem-rt.c
> index 274172d5bb3a..b61edc4dcb73 100644
> --- a/kernel/locking/rwsem-rt.c
> +++ b/kernel/locking/rwsem-rt.c
> @@ -198,7 +198,6 @@ void __up_read(struct rw_semaphore *sem)
>  	if (!atomic_dec_and_test(&sem->readers))
>  		return;
>  
> -	might_sleep();
>  	raw_spin_lock_irq(&m->wait_lock);
>  	/*
>  	 * Wake the writer, i.e. the rtmutex owner. It might release the
> -- 
> 2.30.2
> 

Just a gentle follow up, any feedback?

Thanks,
Andrew