From: Jes Sorensen <jes@wildopensource.com>
To: Russell King <rmk@arm.linux.org.uk>
Cc: linux-kernel@vger.kernel.org, alan@redhat.com,
Marcelo Tosatti <marcelo@conectiva.com.br>
Subject: Re: [patch 2.4] make tty->count atomic_t
Date: 03 Apr 2003 18:18:22 -0500 [thread overview]
Message-ID: <m3of3ndvb5.fsf@trained-monkey.org> (raw)
In-Reply-To: <20030404000608.B18485@flint.arm.linux.org.uk>
>>>>> "Russell" == Russell King <rmk@arm.linux.org.uk> writes:
Russell> On Thu, Apr 03, 2003 at 12:16:21PM -0500, Jes Sorensen wrote:
>> I believe the 2.4 tty code is racey in the way it handles
>> tty->count. release_dev() does the tty->count-- thing without
>> protecting against parallel execution, hence tty->count can end up
>> a random state as
tty-> count-- isn't guaranteed to be atomic (load-store architectures
tty-> and
>> architectures with weak memory ordering etc).
Russell> Isn't release_dev() only called under the BKL, which
Russell> guarantees the old "single-thread in the kernel at a time"
Russell> behaviour from pre-SMP Linux ?
It's called from tty_release() and tty_open(). tty_release() grabs the
BKL but I don't see the path that grabs it when calling through
tty_open() (doesn't mean I am not blind of course ;-).
cheers,
Jes
next prev parent reply other threads:[~2003-04-03 23:07 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-03 17:16 [patch 2.4] make tty->count atomic_t Jes Sorensen
2003-04-03 23:06 ` Russell King
2003-04-03 23:18 ` Jes Sorensen [this message]
2003-04-03 23:28 ` Russell King
2003-04-04 0:13 ` Jes Sorensen
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