linux-kernel - Re: [PATCH -next v2 0/5] ipc/sem: semop(2) improvements

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Date:   Tue, 20 Sep 2016 08:03:28 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     Manfred Spraul <manfred@...orfullife.com>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next v2 0/5] ipc/sem: semop(2) improvements

On Mon, 19 Sep 2016, Manfred Spraul wrote:
>On 09/18/2016 09:11 PM, Davidlohr Bueso wrote:

>>Davidlohr Bueso (5):
>>   ipc/sem: do not call wake_sem_queue_do() prematurely
>The only patch that I don't like.
>Especially: patch 2 of the series removes the wake_up_q from the 
>function epilogue.
>So only the code duplication (additional instances of 
>rcu_read_unlock()) remains, I don't see any advantages.
>
>>   ipc/sem: rework task wakeups
>Acked

Thanks.

>>   ipc/sem: optimize perform_atomic_semop()
>I'm still thinking about it.
>Code duplication is evil, but perhaps it is the best solution.
>
>What I don't like is the hardcoded "< BITS_PER_LONG".
>At least:
>- (1 << sop->sem_num)
>+ (1 << (sop->sem_num%BITS_PER_LONG))

Yeah, I'll send v3 for that.

>>   ipc/sem: explicitly inline check_restart
>Do we really need that? Isn't that the compiler's task?
>Especially since the compiler is already doing it correctly.

Yes, I mentioned in the changelog that the compiler does it and this is
merely explicit. That said I see no harm in it, I guess whatever akpm says.

>>   ipc/sem: use proper list api for pending_list wakeups
>Acked

Thanks,
Davidlohr