Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756262Ab0LLXtu (ORCPT ); Sun, 12 Dec 2010 18:49:50 -0500 Received: from one.firstfloor.org ([213.235.205.2]:36921 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756167Ab0LLXsr (ORCPT ); Sun, 12 Dec 2010 18:48:47 -0500 From: Andi Kleen References: <201012131244.547034648@firstfloor.org> In-Reply-To: <201012131244.547034648@firstfloor.org> To: heiko.carstens@de.ibm.com, schwidefsky@de.ibm.com, gregkh@suse.de, ak@linux.intel.com, linux-kernel@vger.kernel.org, stable@kernel.org Subject: [PATCH] [218/223] nmi: fix clock comparator revalidation Message-Id: <20101212234846.04A9CB27BF@basil.firstfloor.org> Date: Mon, 13 Dec 2010 00:48:45 +0100 (CET) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3625 Lines: 101 2.6.35-longterm review patch. If anyone has any objections, please let me know. ------------------ From: Heiko Carstens commit e8129c642155616d9e2160a75f103e127c8c3708 upstream. On each machine check all registers are revalidated. The save area for the clock comparator however only contains the upper most seven bytes of the former contents, if valid. Therefore the machine check handler uses a store clock instruction to get the current time and writes that to the clock comparator register which in turn will generate an immediate timer interrupt. However within the lowcore the expected time of the next timer interrupt is stored. If the interrupt happens before that time the handler won't be called. In turn the clock comparator won't be reprogrammed and therefore the interrupt condition stays pending which causes an interrupt loop until the expected time is reached. On NOHZ machines this can result in unresponsive machines since the time of the next expected interrupted can be a couple of days in the future. To fix this just revalidate the clock comparator register with the expected value. In addition the special handling for udelay must be changed as well. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman Signed-off-by: Andi Kleen --- arch/s390/kernel/nmi.c | 10 ++++------ arch/s390/lib/delay.c | 14 +++++++++----- 2 files changed, 13 insertions(+), 11 deletions(-) Index: linux/arch/s390/kernel/nmi.c =================================================================== --- linux.orig/arch/s390/kernel/nmi.c +++ linux/arch/s390/kernel/nmi.c @@ -95,7 +95,6 @@ EXPORT_SYMBOL_GPL(s390_handle_mcck); static int notrace s390_revalidate_registers(struct mci *mci) { int kill_task; - u64 tmpclock; u64 zero; void *fpt_save_area, *fpt_creg_save_area; @@ -214,11 +213,10 @@ static int notrace s390_revalidate_regis : "0", "cc"); #endif /* Revalidate clock comparator register */ - asm volatile( - " stck 0(%1)\n" - " sckc 0(%1)" - : "=m" (tmpclock) : "a" (&(tmpclock)) : "cc", "memory"); - + if (S390_lowcore.clock_comparator == -1) + set_clock_comparator(S390_lowcore.mcck_clock); + else + set_clock_comparator(S390_lowcore.clock_comparator); /* Check if old PSW is valid */ if (!mci->wp) /* Index: linux/arch/s390/lib/delay.c =================================================================== --- linux.orig/arch/s390/lib/delay.c +++ linux/arch/s390/lib/delay.c @@ -29,17 +29,21 @@ static void __udelay_disabled(unsigned l { unsigned long mask, cr0, cr0_saved; u64 clock_saved; + u64 end; + mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT; + end = get_clock() + (usecs << 12); clock_saved = local_tick_disable(); - set_clock_comparator(get_clock() + (usecs << 12)); __ctl_store(cr0_saved, 0, 0); cr0 = (cr0_saved & 0xffff00e0) | 0x00000800; __ctl_load(cr0 , 0, 0); - mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT; lockdep_off(); - trace_hardirqs_on(); - __load_psw_mask(mask); - local_irq_disable(); + do { + set_clock_comparator(end); + trace_hardirqs_on(); + __load_psw_mask(mask); + local_irq_disable(); + } while (get_clock() < end); lockdep_on(); __ctl_load(cr0_saved, 0, 0); local_tick_enable(clock_saved); -- 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/