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Re: [PATCH] synchronize_irq needs a barrier

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From: Benjamin Herrenschmidt <benh@...>
To: Linus Torvalds <torvalds@...>
Cc: akpm <akpm@...>, Linux Kernel list <linux-kernel@...>, linuxppc-dev list <linuxppc-dev@...>
Subject: Re: [PATCH] synchronize_irq needs a barrier
Date: Wednesday, October 17, 2007 - 10:57 pm

> 

Take a real life example:

drivers/message/fusion/mptbase.c

	/* Disable interrupts! */
	CHIPREG_WRITE32(&ioc->chip->IntMask, 0xFFFFFFFF);

	ioc->active = 0;
	synchronize_irq(pdev->irq);

And we aren't in a spinlock here. 

That's just a random example grepped.... I think I see a few more. Then,
some drivers like tg3 actually do an smp_mb() before calling
synchronize_irq(). But then, some don't.

I think trying to have all drivers be correct here is asking for
trouble, we'd rather have synchronize_irq() be uber-safe. It's not like
it was used in hot path anyway.

Ben.




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Messages in current thread:
[PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Wed Oct 17, 9:25 pm)
Re: [PATCH] synchronize_irq needs a barrier, Maxim Levitsky, (Fri Oct 19, 10:02 pm)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Fri Oct 19, 11:56 pm)
Re: [PATCH] synchronize_irq needs a barrier, Maxim Levitsky, (Sat Oct 20, 12:24 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Sat Oct 20, 1:04 am)
Re: [PATCH] synchronize_irq needs a barrier, Maxim Levitsky, (Sat Oct 20, 1:36 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Sat Oct 20, 1:46 am)
Re: [PATCH] synchronize_irq needs a barrier, Maxim Levitsky, (Sat Oct 20, 2:06 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Sat Oct 20, 2:13 am)
Re: [PATCH] synchronize_irq needs a barrier, Herbert Xu, (Fri Oct 19, 11:37 pm)
Re: [PATCH] synchronize_irq needs a barrier, Linus Torvalds, (Fri Oct 19, 10:25 pm)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Sat Oct 20, 12:04 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Sat Oct 20, 12:09 am)
Re: [PATCH] synchronize_irq needs a barrier, Maxim Levitsky, (Fri Oct 19, 11:10 pm)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Sat Oct 20, 12:06 am)
Re: [PATCH] synchronize_irq needs a barrier, Linus Torvalds, (Wed Oct 17, 10:12 pm)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Wed Oct 17, 10:40 pm)
Re: [PATCH] synchronize_irq needs a barrier, Herbert Xu, (Thu Oct 18, 10:35 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Thu Oct 18, 5:35 pm)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Wed Oct 17, 10:57 pm)
Re: [PATCH] synchronize_irq needs a barrier, Herbert Xu, (Thu Oct 18, 10:56 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Thu Oct 18, 6:05 pm)
Re: [PATCH] synchronize_irq needs a barrier, Linus Torvalds, (Thu Oct 18, 6:52 pm)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Thu Oct 18, 7:17 pm)
Re: [PATCH] synchronize_irq needs a barrier, Linus Torvalds, (Thu Oct 18, 7:39 pm)
Re: [PATCH] synchronize_irq needs a barrier, Herbert Xu, (Thu Oct 18, 10:32 pm)
Re: [PATCH] synchronize_irq needs a barrier, Linus Torvalds, (Thu Oct 18, 10:55 pm)
Re: [PATCH] synchronize_irq needs a barrier, Linus Torvalds, (Thu Oct 18, 11:26 pm)
Re: [PATCH] synchronize_irq needs a barrier, Herbert Xu, (Fri Oct 19, 12:20 am)
[NET]: Fix possible dev_deactivate race condition, Herbert Xu, (Fri Oct 19, 1:36 am)
Re: [NET]: Fix possible dev_deactivate race condition, Peter Zijlstra, (Fri Oct 19, 3:35 am)
Re: [NET]: Fix possible dev_deactivate race condition, Herbert Xu, (Fri Oct 19, 5:29 am)
Re: [NET]: Fix possible dev_deactivate race condition, David Miller, (Fri Oct 19, 1:38 am)
Re: [PATCH] synchronize_irq needs a barrier, Herbert Xu, (Fri Oct 19, 12:48 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Fri Oct 19, 12:58 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Sun Oct 21, 5:10 pm)
[IRQ]: Fix synchronize_irq races with IRQ handler, Herbert Xu, (Mon Oct 22, 11:26 pm)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Fri Oct 19, 12:35 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Fri Oct 19, 12:29 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Fri Oct 19, 12:11 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Fri Oct 19, 12:26 am)
Re: [PATCH] synchronize_irq needs a barrier, Herbert Xu, (Fri Oct 19, 1:53 am)
Re: [PATCH] synchronize_irq needs a barrier, Nick Piggin, (Thu Oct 18, 10:52 pm)
Re: [PATCH] synchronize_irq needs a barrier, Herbert Xu, (Thu Oct 18, 11:28 pm)
Re: [PATCH] synchronize_irq needs a barrier, Nick Piggin, (Fri Oct 19, 12:49 am)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Thu Oct 18, 7:52 pm)
Re: [PATCH] synchronize_irq needs a barrier, Andrew Morton, (Wed Oct 17, 9:45 pm)
Re: [PATCH] synchronize_irq needs a barrier, Benjamin Herrenschmidt, (Wed Oct 17, 9:55 pm)