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

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Message-ID: <877dkoud19.ffs@nanos.tec.linutronix.de>
Date:   Mon, 26 Apr 2021 20:16:34 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andrew Halaney <ahalaney@...hat.com>, 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 Mon, Apr 26 2021 at 11:42, Andrew Halaney wrote:
> 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?

Looks correct. Will go into the next rt-release.

Thanks,

        tglx