Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754863AbZLBQX3 (ORCPT ); Wed, 2 Dec 2009 11:23:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754718AbZLBQX3 (ORCPT ); Wed, 2 Dec 2009 11:23:29 -0500 Received: from flmx07.ccur.com ([12.192.68.12]:37386 "EHLO flmx07.ccur.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754121AbZLBQX2 (ORCPT ); Wed, 2 Dec 2009 11:23:28 -0500 X-Greylist: delayed 309 seconds by postgrey-1.27 at vger.kernel.org; Wed, 02 Dec 2009 11:23:28 EST Message-ID: <4B169397.5020609@ccur.com> Date: Wed, 2 Dec 2009 10:19:35 -0600 From: John Blackwood User-Agent: Thunderbird 2.0.0.23 (X11/20090812) MIME-Version: 1.0 To: Ingo Molnar , Rusty Russell , "linux-kernel@vger.kernel.org" Subject: [RFC][PATCH] Setting /proc/irq/[n]/smp_affinity failure on 8 cpu systems Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2910 Lines: 76 Hi, I would like to mention an irq set affinity issue occurs on an older Dell PowerEdge 6650 system: - 8 cpus (4 are hyper-threaded), - uses the struct apic 'apic_default' support - 32 bit (x86) kernel This issue is that once you change the irq smp_affinity of an irq to be less than all cpus in the system, you can never change really the irq smp_affinity back to be all cpus in the system (0xff) again, even though no error status is returned on the "/bin/echo ff > /proc/irq/[n]/smp_affinity" operation. This is due to that fact that BAD_APICID has the same value as all cpus (0xff) on 32bit kernels, and thus the value returned from set_desc_affinity() via the cpu_mask_to_apicid_and() function is treated as a failure in set_ioapic_affinity_irq_desc(), and no affinity changes are made. It seems like changing the BAD_APICID value from 0xFF to 0xFFFF for CONFIG_X86_32 might be one possible solution, and it seems to function properly for this Dell PowerEdge 6650 system. Thank you for your time. Signed-off-by: John Blackwood diff -rup linux-2.6.32-rc8/arch/x86/include/asm/apicdef.h new/arch/x86/include/asm/apicdef.h --- linux-2.6.32-rc8/arch/x86/include/asm/apicdef.h 2009-11-19 16:32:38.000000000 -0600 +++ new/arch/x86/include/asm/apicdef.h 2009-12-01 15:15:34.000000000 -0600 @@ -413,9 +413,6 @@ struct local_apic { #undef u32 -#ifdef CONFIG_X86_32 - #define BAD_APICID 0xFFu -#else - #define BAD_APICID 0xFFFFu -#endif +#define BAD_APICID 0xFFFFu + #endif /* _ASM_X86_APICDEF_H */ diff -rup linux-2.6.32-rc8/arch/x86/include/asm/apic.h new/arch/x86/include/asm/apic.h --- linux-2.6.32-rc8/arch/x86/include/asm/apic.h 2009-11-19 16:32:38.000000000 -0600 +++ new/arch/x86/include/asm/apic.h 2009-12-01 15:15:34.000000000 -0600 @@ -591,7 +591,7 @@ static inline physid_mask_t default_apic #endif /* CONFIG_X86_LOCAL_APIC */ #ifdef CONFIG_X86_32 -extern u8 cpu_2_logical_apicid[NR_CPUS]; +extern u16 cpu_2_logical_apicid[NR_CPUS]; #endif #endif /* _ASM_X86_APIC_H */ diff -rup linux-2.6.32-rc8/arch/x86/kernel/smpboot.c new/arch/x86/kernel/smpboot.c --- linux-2.6.32-rc8/arch/x86/kernel/smpboot.c 2009-11-19 16:32:38.000000000 -0600 +++ new/arch/x86/kernel/smpboot.c 2009-12-01 15:15:34.000000000 -0600 @@ -146,7 +146,7 @@ static void unmap_cpu_to_node(int cpu) #ifdef CONFIG_X86_32 static int boot_cpu_logical_apicid; -u8 cpu_2_logical_apicid[NR_CPUS] __read_mostly = +u16 cpu_2_logical_apicid[NR_CPUS] __read_mostly = { [0 ... NR_CPUS-1] = BAD_APICID }; static void map_cpu_to_logical_apicid(void) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/