From: jamie@shareable•org (Jamie Lokier)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH] [ARM] Do not call flush_cache_user_range with mmap_semheld
Date: Thu, 6 May 2010 17:07:52 +0100 [thread overview]
Message-ID: <20100506160752.GE28512@shareable.org> (raw)
In-Reply-To: <20100506160153.GD28512@shareable.org>
Jamie Lokier wrote:
> Catalin Marinas wrote:
> > The flush_cache_user_range operation cannot actually damage the data. If
> > the application is so badly written that one of its threads remaps a
> > page range while another thread writes to it and flushes the caches,
> > then it deserves the memory corruption.
>
> It may deserve corruption, but doing corruption silently is cruel.
>
> Moreover, calling mprotect(PROT_READ) in one thread while another
> thread is writing to the same regions is a valid, and used, garbage
> collector dirty-tracking technique. (Page faults provide the info,
> and the fault handler uses PROT_WRITE to let the faulting thread
> continue on each tracked page.)
>
> Is it possible to percolate EFAULT to the right places when the cache
> flush faults?
Scratch that idea. How about just doing a full mm
(address-independent) cache flush if a fault occurs?
Performance doesn't matter (it's not a normal situation), and it's
better than corruption (no week-long debugging session surprise).
-- Jamie
next prev parent reply other threads:[~2010-05-06 16:07 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-28 7:32 [PATCH] [ARM] Do not call flush_cache_user_range with mmap_sem held Dima Zavin
2010-04-28 7:35 ` Dima Zavin
2010-04-29 13:00 ` Russell King - ARM Linux
2010-04-29 18:16 ` Jamie Lokier
2010-04-29 18:24 ` Russell King - ARM Linux
2010-04-29 19:23 ` Dima Zavin
2010-05-04 4:07 ` Dima Zavin
2010-05-04 7:40 ` Russell King - ARM Linux
2010-05-06 15:00 ` [PATCH] [ARM] Do not call flush_cache_user_range with mmap_semheld Catalin Marinas
2010-05-06 16:01 ` Jamie Lokier
2010-05-06 16:07 ` Jamie Lokier [this message]
2010-05-06 16:24 ` Catalin Marinas
2010-05-06 16:21 ` Catalin Marinas
2010-05-06 15:08 ` [PATCH] [ARM] Do not call flush_cache_user_range with mmap_sem held Catalin Marinas
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