From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761517AbbA2DZB (ORCPT ); Wed, 28 Jan 2015 22:25:01 -0500 Received: from mail-wi0-f177.google.com ([209.85.212.177]:47610 "EHLO mail-wi0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761520AbbA2DYz (ORCPT ); Wed, 28 Jan 2015 22:24:55 -0500 Message-ID: <54C8C017.4050202@linaro.org> Date: Wed, 28 Jan 2015 10:55:19 +0000 From: Daniel Thompson User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Kiran Raparthy , linux-kernel@vger.kernel.org CC: kgdb-bugreport@lists.sourceforge.net, Colin Cross , John Stultz , Jason Wessel , Andrew Morton , Android Kernel Team , Sumit Semwal Subject: Re: [Kgdb-bugreport] [RFC v5 - RESEND] debug: prevent entering debug mode on panic/exception. References: <1422441574-24005-1-git-send-email-kiran.kumar@linaro.org> In-Reply-To: <1422441574-24005-1-git-send-email-kiran.kumar@linaro.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 28/01/15 10:39, Kiran Raparthy wrote: > From: Colin Cross > > debug: prevent entering debug mode on panic/exception. > > On non-developer devices, kgdb prevents the device from rebooting > after a panic. > > Incase of panics and exceptions, to allow the device to reboot, prevent entering > debug mode to avoid getting stuck waiting for the user to interact with debugger. > > To avoid entering the debugger on panic/exception without any extra configuration, > panic_timeout is being used which can be set via /proc/sys/kernel/panic at run time > and CONFIG_PANIC_TIMEOUT sets the default value. > > Setting panic_timeout indicates that the user requested machine to perform > unattended reboot after panic. We dont want to get stuck waiting for the user > input incase of panic. Some kind of changelog between the versions would have been nice. I *think* the difference between v4 and v5 was just the addition paragraph above but I had to put in extra work to check that and I'm still not 100% sure that's the only change. Also you could start billing this as a PATCH rather than an RFC. Daniel. > Cc: Jason Wessel > Cc: Andrew Morton > 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 > Modified the commit as per community feedback] > Signed-off-by: Kiran Raparthy > Reviewed-by: Daniel Thompson > --- > 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(); >