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From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC PATCH] uprobes: copy to user-space xol page with proper cache flushing
Date: Fri, 11 Apr 2014 17:00:29 +0100	[thread overview]
Message-ID: <20140411160028.GR16119@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <20140411153249.GZ11096@twins.programming.kicks-ass.net>

On Fri, Apr 11, 2014 at 05:32:49PM +0200, Peter Zijlstra wrote:
> On Fri, Apr 11, 2014 at 05:22:07PM +0200, Oleg Nesterov wrote:
> > And I am just curious, why arm's copy_to_user_page() disables premption
> > before memcpy?
> 
> Without looking, I suspect its because the VIVT caches, they need to get
> shot down on every context switch.

So... let's think about that for a moment... if we have a preemption event,
then that's a context switch, which means...

No, this is obviously not the reason, because such an event on a fully
VIVT system would result in the caches being flushed, meaning that we
wouldn't need to do anything if we could be predicably preempted at that
point.

-- 
FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.

  reply	other threads:[~2014-04-11 16:00 UTC|newest]

Thread overview: 66+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-04-09  5:58 [PATCH v2] ARM: uprobes need icache flush after xol write Victor Kamensky
2014-04-09  5:58 ` Victor Kamensky
2014-04-09 18:23   ` David Long
2014-04-09 18:45   ` Oleg Nesterov
2014-04-09 19:13     ` Victor Kamensky
2014-04-09 19:19       ` Russell King - ARM Linux
2014-04-11  3:42       ` [RFC PATCH] uprobes: copy to user-space xol page with proper cache flushing David Long
2014-04-11  3:45       ` David Long
2014-04-11  4:36         ` David Miller
2014-04-11 14:26           ` Victor Kamensky
2014-04-11 14:35             ` Oleg Nesterov
2014-04-11 14:55             ` Victor Kamensky
2014-04-11 14:56           ` Oleg Nesterov
2014-04-11 15:22             ` Oleg Nesterov
2014-04-11 15:30               ` Russell King - ARM Linux
2014-04-11 17:24                 ` Oleg Nesterov
2014-04-11 17:38                   ` Oleg Nesterov
2014-04-11 18:00                     ` David Miller
2014-04-11 18:25                       ` Oleg Nesterov
2014-04-11 17:50                   ` Linus Torvalds
2014-04-11 18:02                     ` David Miller
2014-04-11 18:11                       ` Linus Torvalds
2014-04-11 18:19                         ` David Miller
2014-04-11 18:24                           ` Linus Torvalds
2014-04-11 18:58                             ` David Miller
2014-04-11 19:24                               ` Linus Torvalds
2014-04-11 18:13                       ` Victor Kamensky
2014-04-11 18:36                         ` Oleg Nesterov
2014-04-14 18:59                     ` Oleg Nesterov
2014-04-14 20:05                       ` Victor Kamensky
2014-04-14 21:40                         ` Victor Kamensky
2014-04-15 16:26                           ` Oleg Nesterov
2014-04-15 15:46                         ` Oleg Nesterov
2014-04-15 16:46                           ` Victor Kamensky
2014-04-15 17:19                           ` David Long
2014-04-15 17:38                             ` David Miller
2014-04-15 17:49                               ` Oleg Nesterov
2014-04-15 17:50                                 ` David Miller
2014-04-15 18:07                                   ` Oleg Nesterov
2014-04-15 18:27                                     ` David Miller
2014-04-15 18:46                                       ` Oleg Nesterov
2014-04-15 17:43                             ` Oleg Nesterov
2014-04-15 17:46                               ` David Miller
2014-04-15 18:03                                 ` Oleg Nesterov
2014-04-15 18:30                                   ` David Miller
2014-04-15 18:47                                     ` Russell King - ARM Linux
2014-04-15 18:53                                       ` David Miller
2014-04-15 18:50                                     ` David Miller
2014-04-15 19:29                                       ` Russell King - ARM Linux
2014-04-15 19:51                                         ` David Miller
2014-04-15 19:39                               ` David Long
2014-04-15 19:53                                 ` David Miller
2014-04-16  1:42                                   ` Victor Kamensky
2014-04-16  2:22                                     ` David Miller
2014-04-16  2:24                                     ` David Miller
2014-04-16  3:06                                       ` Victor Kamensky
2014-04-16  3:17                                         ` David Miller
2014-04-11 17:43                 ` David Miller
2014-04-11 15:32               ` Peter Zijlstra
2014-04-11 16:00                 ` Russell King - ARM Linux [this message]
2014-04-11 18:39                   ` Peter Zijlstra
2014-04-11 15:37             ` Victor Kamensky
2014-04-11 16:22               ` Oleg Nesterov
2014-04-11 15:42             ` Linus Torvalds
2014-04-11 13:08         ` Oleg Nesterov
2014-04-23 10:45         ` Catalin Marinas

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