netdev - Re: [patch (testing)] Re: 2.6.20->2.6.21 - networking dies after random time

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Date:	Fri, 10 Aug 2007 11:38:39 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Jarek Poplawski <jarkao2@...pl>
Cc:	Jean-Baptiste Vignaud <vignaud@...dmail.fr>,
	"marcin.slusarz" <marcin.slusarz@...il.com>,
	tglx <tglx@...utronix.de>,
	torvalds <torvalds@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	shemminger <shemminger@...ux-foundation.org>,
	linux-net <linux-net@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	akpm <akpm@...ux-foundation.org>, alan <alan@...rguk.ukuu.org.uk>
Subject: Re: [patch (testing)] Re: 2.6.20->2.6.21 - networking dies after
	random time


* Jarek Poplawski <jarkao2@...pl> wrote:

> All correct! There was also checked a possibility it can be not hw 
> itself, but wrong way of handling after hw (acking too late). This was 
> false idea (or bad implementation), so it looks like hw vs lapic 
> problem.

i think the problem is that local APIC 'self vectors' might be 
edge-triggered by default. I'm not exactly sure whether passing in 
APIC_INT_LEVELTRIG to send_IPI_self() will truly be interpreted by the 
local APIC into any external IO-APIC ACK sequence (the local APIC might 
just treat self-vectors as always-edge) - and it might also be that the 
pure act of mixing self-triggered vectors with level-triggered external 
irqs sometimes confuses the IO-APIC <-> local-APIC messaging. One more 
test of the patch below will tell us a bit more about this part of the 
story.

	Ingo

Index: linux/arch/i386/kernel/io_apic.c
===================================================================
--- linux.orig/arch/i386/kernel/io_apic.c
+++ linux/arch/i386/kernel/io_apic.c
@@ -735,7 +735,8 @@ void fastcall send_IPI_self(int vector)
 	 * Wait for idle.
 	 */
 	apic_wait_icr_idle();
-	cfg = APIC_DM_FIXED | APIC_DEST_SELF | vector | APIC_DEST_LOGICAL;
+	cfg = APIC_DM_FIXED | APIC_DEST_SELF | vector | APIC_DEST_LOGICAL |
+		APIC_INT_LEVELTRIG;
 	/*
 	 * Send the IPI. The write to APIC_ICR fires this off.
 	 */
-
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