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From: Andrew Morton <akpm@osdl.org>
To: Zwane Mwaikambo <zwane@arm.linux.org.uk>
Cc: oxymoron@waste.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] [1/2] random: SMP locking
Date: Sat, 2 Aug 2003 11:39:07 -0700	[thread overview]
Message-ID: <20030802113907.30e1d001.akpm@osdl.org> (raw)
In-Reply-To: <Pine.LNX.4.53.0308020832520.3473@montezuma.mastecende.com>

Zwane Mwaikambo <zwane@arm.linux.org.uk> wrote:
>
> Perhaps might_sleep() in *_user, copy_* etc is in order?

Probably, with a little care.

A userspace copy while in an atomic region is actually legal, on behalf of
the read() and write() pagecache copy functions: if we take a fault while
holding an atomic kmap, the fault handler bales and the usercopy returns a
short copy.

In other words: if you stick a might_sleep() in __copy_from_user() and
__copy_to_user() you get a false positive on every read() and write().

We could probably add it to copy_to_user() and copy_from_user() though.

  parent reply	other threads:[~2003-08-02 18:38 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-08-02  4:24 [PATCH] [1/2] random: SMP locking Oliver Xymoron
2003-08-02 11:00 ` Andrew Morton
2003-08-02 12:35   ` Zwane Mwaikambo
2003-08-02 14:43     ` Matt Mackall
2003-08-02 15:02       ` Zwane Mwaikambo
2003-08-02 18:39     ` Andrew Morton [this message]
2003-08-02 18:42     ` Matt Mackall
2003-08-02 14:32   ` Matt Mackall
2003-08-02 19:00     ` Andrew Morton
2003-08-02 19:33       ` Matt Mackall
2003-08-02 19:46         ` Andrew Morton
2003-08-02 20:14           ` Matt Mackall

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