linux-kernel - Re: [PATCH] kasan: convert kasan/quarantine_lock to raw

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Date:   Wed, 10 Oct 2018 11:57:41 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     Clark Williams <williams@...hat.com>,
        Alexander Potapenko <glider@...gle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-rt-users@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] kasan: convert kasan/quarantine_lock to raw_spinlock

On Wed, Oct 10, 2018 at 11:53 AM, Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
> On 2018-10-10 11:45:32 [+0200], Dmitry Vyukov wrote:
>> > Should I repost Clark's patch?
>>
>>
>> I am much more comfortable with just changing the type of the lock.
>
> Yes, that is what Clark's patch does. Should I resent it?


Yes. Clark's patch looks good to me. Probably would be useful to add a
comment as to why raw spinlock is used (otherwise somebody may
refactor it back later).


>> What are the bad implications of using the raw spinlock? Will it help
>> to do something along the following lines:
>>
>> // Because of ...
>> #if CONFIG_RT
>> #define quarantine_spinlock_t raw_spinlock_t
>> #else
>> #define quarantine_spinlock_t spinlock_t
>> #endif
>
> no. For !RT spinlock_t and raw_spinlock_t are the same. For RT
> spinlock_t does not disable interrupts or preemption while
> raw_spinlock_t does.
> Therefore holding a raw_spinlock_t might increase your latency.

Ack.