From: Andrea Arcangeli <andrea@suse.de>
To: Stephan von Krawczynski <skraw@ithnet.com>,
manfred@colorfullife.com, linux-kernel@vger.kernel.org,
zwane@linuxpower.ca
Cc: TeJun Huh <tejun@aratech.co.kr>
Subject: Re: Possible race condition in i386 global_irq_lock handling.
Date: Fri, 22 Aug 2003 18:25:46 +0200 [thread overview]
Message-ID: <20030822162546.GQ29612@dualathlon.random> (raw)
In-Reply-To: <20030822011840.GA14540@atj.dyndns.org>
thanks TeJun,
just one comment
On Fri, Aug 22, 2003 at 10:18:40AM +0900, TeJun Huh wrote:
> 3. remove irqs_running() test from synchronize_irq()
I'm not convinced this one is needed. An irq can still run on another
cpu but the cli();sti() may execute while it's here:
irq running synchronize_irq()
-------------- -----------------
do_IRQ
handle_IRQ_event
cli()
sti()
irq_enter -> way too late
in short, doing irqs_running() doesn't seem to weaken the semantics of
synchronize_irq() to me.
I think it should be changed this way instead:
void synchronize_irq(void)
{
smp_mb();
if (irqs_running()) {
/* Stupid approach */
cli();
sti();
}
}
to be sure to read the local irq area after the previous code (the
test_and_set_bit of the global_irq_lock of a cli() in your version would
achieve the same implicit smp_mb too, so maybe your only point for doing
cli()/sti() was to execute the smp_mb before the irqs_running?). the
above version is more finegrined and it looks equivalent to yours.
Andrea
next prev parent reply other threads:[~2003-08-23 18:29 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-08-21 17:01 Possible race condition in i386 global_irq_lock handling Manfred Spraul
2003-08-21 17:27 ` Andrea Arcangeli
2003-08-21 21:48 ` Stephan von Krawczynski
2003-08-21 22:44 ` Andrea Arcangeli
2003-08-22 1:18 ` TeJun Huh
2003-08-22 10:07 ` Stephan von Krawczynski
2003-08-22 16:25 ` Andrea Arcangeli [this message]
2003-08-24 3:06 ` TeJun Huh
2003-08-24 22:03 ` Andrea Arcangeli
-- strict thread matches above, loose matches on Subject: below --
2003-08-21 8:48 TeJun Huh
2003-08-21 10:07 ` Zwane Mwaikambo
2003-08-21 16:15 ` TeJun Huh
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