Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753860AbaLHFR5 (ORCPT ); Mon, 8 Dec 2014 00:17:57 -0500 Received: from mail-qg0-f43.google.com ([209.85.192.43]:62568 "EHLO mail-qg0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750776AbaLHFR4 (ORCPT ); Mon, 8 Dec 2014 00:17:56 -0500 MIME-Version: 1.0 In-Reply-To: References: <1416993266-16514-1-git-send-email-kiran.kumar@linaro.org> <5476F3C5.8020709@linaro.org> Date: Mon, 8 Dec 2014 10:47:54 +0530 Message-ID: Subject: Re: [RFC v3] debug: prevent entering debug mode on errors From: Kiran Raparthy To: Daniel Thompson Cc: Colin Cross , lkml , Jason Wessel , kgdb-bugreport@lists.sourceforge.net, Android Kernel Team , John Stultz , Sumit Semwal Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jason, On 1 December 2014 at 11:32, Kiran Raparthy wrote: > Hi Jason, > > On 27 November 2014 at 15:19, Daniel Thompson > wrote: >> On 26/11/14 17:45, Colin Cross wrote: >>> On Wed, Nov 26, 2014 at 1:14 AM, Kiran Raparthy wrote: >>>> From: Colin Cross >>>> >>>> debug: prevent entering debug mode on errors >>>> >>>> On non-developer devices kgdb prevents CONFIG_PANIC_TIMEOUT from rebooting the >>>> device after a panic. >>>> >>>> In case of panics and exceptions, to honor CONFIG_PANIC_TIMEOUT, prevent >>>> entering debug mode to avoid getting stuck waiting for the user to interact >>>> with debugger. >>>> >>>> Cc: Jason Wessel >>>> Cc: kgdb-bugreport@lists.sourceforge.net >>>> Cc: linux-kernel@vger.kernel.org >>>> Cc: Android Kernel Team >>>> Cc: John Stultz >>>> Cc: Sumit Semwal >>>> Signed-off-by: Colin Cross >>>> [Kiran: Added context to commit message. >>>> panic_timeout is used instead of break_on_panic and >>>> break_on_exception to honor CONFIG_PANIC_TIMEOUT] >>>> Signed-off-by: Kiran Raparthy >>>> --- >>>> kernel/debug/debug_core.c | 17 +++++++++++++++++ >>>> 1 file changed, 17 insertions(+) >>>> >>>> diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c >>>> index 1adf62b..0012a1f 100644 >>>> --- a/kernel/debug/debug_core.c >>>> +++ b/kernel/debug/debug_core.c >>>> @@ -689,6 +689,14 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) >>>> >>>> if (arch_kgdb_ops.enable_nmi) >>>> arch_kgdb_ops.enable_nmi(0); >>>> + /* >>>> + * Avoid entering the debugger if we were triggered due to an oops >>>> + * but panic_timeout indicates the system should automatically >>>> + * reboot on panic. We don't want to get stuck waiting for input >>>> + * on such systems, especially if its "just" an oops. >>>> + */ >>>> + if (signo != SIGTRAP && panic_timeout) >>>> + return 1; >>>> >>>> memset(ks, 0, sizeof(struct kgdb_state)); >>>> ks->cpu = raw_smp_processor_id(); >>>> @@ -821,6 +829,15 @@ static int kgdb_panic_event(struct notifier_block *self, >>>> unsigned long val, >>>> void *data) >>>> { >>>> + /* >>>> + * Avoid entering the debugger if we were triggered due to a panic >>>> + * We don't want to get stuck waiting for input from user in such case. >>>> + * panic_timeout indicates the system should automatically >>>> + * reboot on panic. >>>> + */ >>>> + if (panic_timeout) >>>> + return NOTIFY_DONE; >>>> + >>>> if (dbg_kdb_mode) >>>> kdb_printf("PANIC: %s\n", (char *)data); >>>> kgdb_breakpoint(); >>> >>> The original patch was more useful as it allowed re-enabling break on >>> panic on specific devices where you were trying to debug a >>> reproducible issue. What about using a module_param similar to >>> kgdbreboot, but setting the default based on CONFIG_PANIC_TIMEOUT to >>> avoid extra configuration? >> >> This change was due to my review so perhaps I'd better answer this... >> >> panic_timeout is the value of the panic sysctl. In addition to the >> normal sysctl tooling (which I don't think is available on most android >> systems), its value can be set using panic=0 on the kernel command line >> or via /proc/sys/kernel/panic at runtime. >> >> CONFIG_PANIC_TIMEOUT merely sets the default value of the sysctl. I >> guess perhaps the patch description could be improved to make this clearer. >> >> Therefore, the only loss of function I expected versus the original is >> that it would be hard to get as far as a reproducible panic if the >> system also has a ton of reproducible oopses that we don't want to fix. >> Is such a use-case important? > > Could you please let me know if this patch is good to move from RFC to PATCH? Just a gentle reminder. Regards, Kiran > Regards, > Kiran -- 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/