linux-kernel - Re: [RFC v3] debug: prevent entering debug mode on errors

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Date:	Wed, 26 Nov 2014 15:00:10 +0530
From:	Kiran Raparthy <kiran.kumar@...aro.org>
To:	Daniel Thompson <daniel.thompson@...aro.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Colin Cross <ccross@...roid.com>,
	Jason Wessel <jason.wessel@...driver.com>,
	kgdb-bugreport@...ts.sourceforge.net,
	Android Kernel Team <kernel-team@...roid.com>,
	John Stultz <john.stultz@...aro.org>,
	Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [RFC v3] debug: prevent entering debug mode on errors

On 26 November 2014 at 14:56, Daniel Thompson
<daniel.thompson@...aro.org> wrote:
> On 26/11/14 09:14, Kiran Raparthy wrote:
>> From: Colin Cross <ccross@...roid.com>
>>
>> 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 <jason.wessel@...driver.com>
>> Cc: kgdb-bugreport@...ts.sourceforge.net
>> Cc: linux-kernel@...r.kernel.org
>> Cc: Android Kernel Team <kernel-team@...roid.com>
>> Cc: John Stultz <john.stultz@...aro.org>
>> Cc: Sumit Semwal <sumit.semwal@...aro.org>
>> Signed-off-by: Colin Cross <ccross@...roid.com>
>> [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 <kiran.kumar@...aro.org>
>
> When this gets upgrade from RFC to PATCH then feel free to add:
> Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org>
Sure.
Regards,
Kiran
>
>> ---
>>  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();
>>
>
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