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From: Dmitry Vyukov <dvyukov@google.com>
Date: Wed, 10 Oct 2018 11:57:41 +0200
Message-ID: <CACT4Y+ZpMjYBPS0GHP0AsEJZZmDjwV9DJBiVUzYKBnD+r9W4+A@mail.gmail.com>
Subject: Re: [PATCH] kasan: convert kasan/quarantine_lock to raw_spinlock
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To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Clark Williams <williams@redhat.com>, Alexander Potapenko <glider@google.com>, kasan-dev <kasan-dev@googlegroups.com>, Linux-MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, linux-rt-users@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, Thomas Gleixner <tglx@linutronix.de>

On Wed, Oct 10, 2018 at 11:53 AM, Sebastian Andrzej Siewior
<bigeasy@linutronix.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.