From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756228AbaFXQW5 (ORCPT ); Tue, 24 Jun 2014 12:22:57 -0400 Received: from mail-qc0-f175.google.com ([209.85.216.175]:49923 "EHLO mail-qc0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756192AbaFXQWx (ORCPT ); Tue, 24 Jun 2014 12:22:53 -0400 Date: Tue, 24 Jun 2014 12:22:50 -0400 (EDT) From: Nicolas Pitre To: Daniel Thompson cc: Russell King , Anton Vorontsov , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kgdb-bugreport@lists.sourceforge.net, patches@linaro.org, linaro-kernel@lists.linaro.org, John Stultz , Colin Cross , kernel-team@android.com, Rob Herring , Linus Walleij , Ben Dooks , Catalin Marinas , Dave Martin , Fabio Estevam , Frederic Weisbecker Subject: Re: [PATCH v6 4/4] ARM: Add KGDB/KDB FIQ debugger generic code In-Reply-To: <1403623097-1153-5-git-send-email-daniel.thompson@linaro.org> Message-ID: References: <1403174303-25456-1-git-send-email-daniel.thompson@linaro.org> <1403623097-1153-1-git-send-email-daniel.thompson@linaro.org> <1403623097-1153-5-git-send-email-daniel.thompson@linaro.org> User-Agent: Alpine 2.11 (LFD 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 24 Jun 2014, Daniel Thompson wrote: > From: Anton Vorontsov > > The FIQ debugger may be used to debug situations when the kernel stuck > in uninterruptable sections, e.g. the kernel infinitely loops or > deadlocked in an interrupt or with interrupts disabled. > > By default KGDB FIQ is disabled in runtime, but can be enabled with > kgdb_fiq.enable=1 kernel command line option. > > Signed-off-by: Anton Vorontsov > Signed-off-by: John Stultz > Signed-off-by: Daniel Thompson > Cc: Russell King > Cc: Ben Dooks > Cc: Dave Martin > --- > arch/arm/Kconfig | 2 + > arch/arm/Kconfig.debug | 18 ++++++ > arch/arm/include/asm/kgdb.h | 7 +++ > arch/arm/kernel/Makefile | 1 + > arch/arm/kernel/kgdb_fiq.c | 124 +++++++++++++++++++++++++++++++++++++++ > arch/arm/kernel/kgdb_fiq_entry.S | 87 +++++++++++++++++++++++++++ > 6 files changed, 239 insertions(+) > create mode 100644 arch/arm/kernel/kgdb_fiq.c > create mode 100644 arch/arm/kernel/kgdb_fiq_entry.S [...] > +static long kgdb_fiq_setup_stack(void *info) > +{ > + struct pt_regs regs; > + > + regs.ARM_sp = __get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER) + > + THREAD_START_SP; > + WARN_ON(!regs.ARM_sp); Isn't this rather fatal if you can't allocate any stack? Why not using BUG_ON(), or better yet propagate a proper error code back? > + > + set_fiq_regs(®s); > + return 0; > +} > + > +/** > + * kgdb_fiq_enable_nmi - Manage NMI-triggered entry to KGDB > + * @on: Flag to either enable or disable an NMI > + * > + * This function manages NMIs that usually cause KGDB to enter. That is, not > + * all NMIs should be enabled or disabled, but only those that issue > + * kgdb_handle_exception(). > + * > + * The call counts disable requests, and thus allows to nest disables. But > + * trying to enable already enabled NMI is an error. > + */ > +static void kgdb_fiq_enable_nmi(bool on) > +{ > + static atomic_t cnt; > + int ret; > + > + ret = atomic_add_return(on ? 1 : -1, &cnt); > + if (ret > 1 && on) { > + /* > + * There should be only one instance that calls this function > + * in "enable, disable" order. All other users must call > + * disable first, then enable. If not, something is wrong. > + */ > + WARN_ON(1); > + return; > + } Minor style suggestion: /* * There should be only one instance that calls this function * in "enable, disable" order. All other users must call * disable first, then enable. If not, something is wrong. */ if (WARN_ON(ret > 1 && on)) return; Other than that... Acked-by: Nicolas Pitre Nicolas From mboxrd@z Thu Jan 1 00:00:00 1970 From: nicolas.pitre@linaro.org (Nicolas Pitre) Date: Tue, 24 Jun 2014 12:22:50 -0400 (EDT) Subject: [PATCH v6 4/4] ARM: Add KGDB/KDB FIQ debugger generic code In-Reply-To: <1403623097-1153-5-git-send-email-daniel.thompson@linaro.org> References: <1403174303-25456-1-git-send-email-daniel.thompson@linaro.org> <1403623097-1153-1-git-send-email-daniel.thompson@linaro.org> <1403623097-1153-5-git-send-email-daniel.thompson@linaro.org> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, 24 Jun 2014, Daniel Thompson wrote: > From: Anton Vorontsov > > The FIQ debugger may be used to debug situations when the kernel stuck > in uninterruptable sections, e.g. the kernel infinitely loops or > deadlocked in an interrupt or with interrupts disabled. > > By default KGDB FIQ is disabled in runtime, but can be enabled with > kgdb_fiq.enable=1 kernel command line option. > > Signed-off-by: Anton Vorontsov > Signed-off-by: John Stultz > Signed-off-by: Daniel Thompson > Cc: Russell King > Cc: Ben Dooks > Cc: Dave Martin > --- > arch/arm/Kconfig | 2 + > arch/arm/Kconfig.debug | 18 ++++++ > arch/arm/include/asm/kgdb.h | 7 +++ > arch/arm/kernel/Makefile | 1 + > arch/arm/kernel/kgdb_fiq.c | 124 +++++++++++++++++++++++++++++++++++++++ > arch/arm/kernel/kgdb_fiq_entry.S | 87 +++++++++++++++++++++++++++ > 6 files changed, 239 insertions(+) > create mode 100644 arch/arm/kernel/kgdb_fiq.c > create mode 100644 arch/arm/kernel/kgdb_fiq_entry.S [...] > +static long kgdb_fiq_setup_stack(void *info) > +{ > + struct pt_regs regs; > + > + regs.ARM_sp = __get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER) + > + THREAD_START_SP; > + WARN_ON(!regs.ARM_sp); Isn't this rather fatal if you can't allocate any stack? Why not using BUG_ON(), or better yet propagate a proper error code back? > + > + set_fiq_regs(®s); > + return 0; > +} > + > +/** > + * kgdb_fiq_enable_nmi - Manage NMI-triggered entry to KGDB > + * @on: Flag to either enable or disable an NMI > + * > + * This function manages NMIs that usually cause KGDB to enter. That is, not > + * all NMIs should be enabled or disabled, but only those that issue > + * kgdb_handle_exception(). > + * > + * The call counts disable requests, and thus allows to nest disables. But > + * trying to enable already enabled NMI is an error. > + */ > +static void kgdb_fiq_enable_nmi(bool on) > +{ > + static atomic_t cnt; > + int ret; > + > + ret = atomic_add_return(on ? 1 : -1, &cnt); > + if (ret > 1 && on) { > + /* > + * There should be only one instance that calls this function > + * in "enable, disable" order. All other users must call > + * disable first, then enable. If not, something is wrong. > + */ > + WARN_ON(1); > + return; > + } Minor style suggestion: /* * There should be only one instance that calls this function * in "enable, disable" order. All other users must call * disable first, then enable. If not, something is wrong. */ if (WARN_ON(ret > 1 && on)) return; Other than that... Acked-by: Nicolas Pitre Nicolas