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Date: Wed, 10 Oct 2018 11:53:43 +0200
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: Re: [PATCH] kasan: convert kasan/quarantine_lock to raw_spinlock
Message-ID: <20181010095343.6qxved3owi6yokoa@linutronix.de>
References: <20180918152931.17322-1-williams@redhat.com>
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To: Dmitry Vyukov <dvyukov@google.com>
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 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?

> 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.

Sebastian