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Date:   Wed, 7 Apr 2021 17:51:07 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Christoph =?iso-8859-1?Q?M=FCllner?= <christophm30@gmail.com>
Cc:     Christoph Hellwig <hch@infradead.org>, Guo Ren <guoren@kernel.org>,
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Subject: Re: [PATCH v4 3/4] locking/qspinlock: Add
 ARCH_USE_QUEUED_SPINLOCKS_XCHG32
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On Wed, Apr 07, 2021 at 04:29:12PM +0200, Christoph Müllner wrote:
> Further, it is not the case that RISC-V has no guarantees at all.
> It just does not provide a forward progress guarantee for a
> synchronization implementation,
> that writes in an endless loop to a memory location while trying to
> complete an LL/SC
> loop on the same memory location at the same time.

Userspace can DoS the kernel that way, see futex.