From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 8FAD51A0021 for ; Mon, 11 May 2015 10:49:14 +1000 (AEST) Received: from mail-pa0-x230.google.com (mail-pa0-x230.google.com [IPv6:2607:f8b0:400e:c03::230]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 83E54140187 for ; Mon, 11 May 2015 10:49:12 +1000 (AEST) Received: by pabtp1 with SMTP id tp1so96286282pab.2 for ; Sun, 10 May 2015 17:49:10 -0700 (PDT) From: Daniel Axtens To: linuxppc-dev@ozlabs.org Subject: [PATCH] powerpc/mce: fix off by one errors in mce event handling Date: Mon, 11 May 2015 10:48:32 +1000 Message-Id: <1431305312-9955-1-git-send-email-dja@axtens.net> Cc: Mahesh Salgaonkar , Daniel Axtens , stable@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Before 69111bac42f5 ("powerpc: Replace __get_cpu_var uses"), in save_mce_event, index got the value of mce_nest_count, and mce_nest_count was incremented *after* index was set. However, that patch changed the behaviour so that mce_nest count was incremented *before* setting index. This causes an off-by-one error, as get_mce_event sets index as mce_nest_count - 1 before reading mce_event. Thus get_mce_event reads bogus data, causing warnings like "Machine Check Exception, Unknown event version 0 !" and breaking MCEs handling. Restore the old behaviour and unbreak MCE handling by moving the increment to after index is set. The same broken change occured in machine_check_queue_event (which set a queue read by machine_check_process_queued_event). Fix that too, unbreaking printing of MCE information. Fixes: 69111bac42f5 ("powerpc: Replace __get_cpu_var uses") CC: stable@vger.kernel.org CC: Mahesh Salgaonkar Signed-off-by: Daniel Axtens --- arch/powerpc/kernel/mce.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c index 15c99b6..f774b64 100644 --- a/arch/powerpc/kernel/mce.c +++ b/arch/powerpc/kernel/mce.c @@ -73,8 +73,9 @@ void save_mce_event(struct pt_regs *regs, long handled, uint64_t nip, uint64_t addr) { uint64_t srr1; - int index = __this_cpu_inc_return(mce_nest_count); + int index = __this_cpu_read(mce_nest_count); struct machine_check_event *mce = this_cpu_ptr(&mce_event[index]); + __this_cpu_inc(mce_nest_count); /* * Return if we don't have enough space to log mce event. @@ -184,7 +185,8 @@ void machine_check_queue_event(void) if (!get_mce_event(&evt, MCE_EVENT_RELEASE)) return; - index = __this_cpu_inc_return(mce_queue_count); + index = __this_cpu_read(mce_queue_count); + __this_cpu_inc(mce_queue_count); /* If queue is full, just return for now. */ if (index >= MAX_MC_EVT) { __this_cpu_dec(mce_queue_count); -- 2.1.4