From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754166AbaEONZ2 (ORCPT ); Thu, 15 May 2014 09:25:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32204 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753460AbaEONZY (ORCPT ); Thu, 15 May 2014 09:25:24 -0400 From: Prarit Bhargava To: linux-kernel@vger.kernel.org Cc: Yinghai Lu , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Prarit Bhargava , Andi Kleen , "K. Y. Srinivasan" , "Steven Rostedt (Red Hat)" , "Elliott, Robert (Server Storage)" Subject: [PATCH 1/2 v2] x86, irq: get correct available vectors for cpu disable Date: Thu, 15 May 2014 09:25:04 -0400 Message-Id: <1400160305-17774-2-git-send-email-prarit@redhat.com> In-Reply-To: <1400160305-17774-1-git-send-email-prarit@redhat.com> References: <1400160305-17774-1-git-send-email-prarit@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yinghai Lu check_irq_vectors_for_cpu_disable() may overestimate the number of available vectors assigned to a cpu. This can cause cpu remove to erroneously fail. commit da6139e49c7cb0f4251265cb5243b8d220adb48d, x86: Add check for number of available vectors before CPU down, introduces a check to see if there are enough empty vectors in the system to replace a downed cpu's vectors. Code inspection shows that the range used in the check (currently from FIRST_EXTERNAL_VECTOR to NR_VECTORS) is incorrect and should be FIRST_EXTERNAL_VECTOR to first_system_vector. The value of first_system_vector is decremented when system vectors are assigned in alloc_system_vector(). The check_irq_vectors_for_cpu_disable() check also does not take into account the first 32 system vectors which are not managed in the per_cpu vector_irq arrays, including IA32_SYSCALL_VECTOR (0x80) and the IRQ_MOVE_CLEANUP_VECTOR (0x20). Cc: Thomas Gleixner Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: x86@kernel.org Cc: Prarit Bhargava Cc: Andi Kleen Cc: "K. Y. Srinivasan" Cc: "Steven Rostedt (Red Hat)" Cc: Yinghai Lu Cc: "Elliott, Robert (Server Storage)" Signed-off-by: Yinghai Lu [v2]: fixed up typos --- arch/x86/kernel/irq.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index 283a76a..276b02b 100644 --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -17,6 +17,7 @@ #include #include #include +#include #define CREATE_TRACE_POINTS #include @@ -334,8 +335,21 @@ int check_irq_vectors_for_cpu_disable(void) for_each_online_cpu(cpu) { if (cpu == this_cpu) continue; - for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; - vector++) { + + /* + * assign_irq_vector() only scans per_cpu vectors from + * FIRST_EXTERNAL_VECTOR to first_system_vector. + * It also skips vectors that are set in used_vectors bitmask. + * used_vectors could have bits set for + * IA32_SYSCALL_VECTOR (0x80) + * IRQ_MOVE_CLEANUP_VECTOR (0x20) + * Don't count those as available vectors. + */ + for (vector = FIRST_EXTERNAL_VECTOR; + vector < first_system_vector; vector++) { + if (test_bit(vector, used_vectors)) + continue; + if (per_cpu(vector_irq, cpu)[vector] < 0) count++; } -- 1.7.9.3