[RFC v3] debug: prevent entering debug mode on errors

[RFC v3] debug: prevent entering debug mode on errors

[Kiran Raparthy]

From: Colin Cross <ccross@android.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@windriver.com>
Cc: kgdb-bugreport@lists.sourceforge.net
Cc: linux-kernel@vger.kernel.org
Cc: Android Kernel Team <kernel-team@android.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Signed-off-by: Colin Cross <ccross@android.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@linaro.org>
---
 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();
-- 
1.8.2.1

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

[Daniel Thompson]

On 26/11/14 09:14, Kiran Raparthy wrote:
> From: Colin Cross <ccross@android.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@windriver.com>
> Cc: kgdb-bugreport@lists.sourceforge.net
> Cc: linux-kernel@vger.kernel.org
> Cc: Android Kernel Team <kernel-team@android.com>
> Cc: John Stultz <john.stultz@linaro.org>
> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> Signed-off-by: Colin Cross <ccross@android.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@linaro.org>

When this gets upgrade from RFC to PATCH then feel free to add:
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>

> ---
>  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();
> 

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

[Kiran Raparthy]

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

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

[Colin Cross]

On Wed, Nov 26, 2014 at 1:14 AM, Kiran Raparthy <kiran.kumar@linaro.org> wrote:
> From: Colin Cross <ccross@android.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@windriver.com>
> Cc: kgdb-bugreport@lists.sourceforge.net
> Cc: linux-kernel@vger.kernel.org
> Cc: Android Kernel Team <kernel-team@android.com>
> Cc: John Stultz <john.stultz@linaro.org>
> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> Signed-off-by: Colin Cross <ccross@android.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@linaro.org>
> ---
>  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();
> --
> 1.8.2.1
>
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.

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?

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

[Daniel Thompson]

On 26/11/14 17:45, Colin Cross wrote:
> On Wed, Nov 26, 2014 at 1:14 AM, Kiran Raparthy <kiran.kumar@linaro.org> wrote:
>> From: Colin Cross <ccross@android.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@windriver.com>
>> Cc: kgdb-bugreport@lists.sourceforge.net
>> Cc: linux-kernel@vger.kernel.org
>> Cc: Android Kernel Team <kernel-team@android.com>
>> Cc: John Stultz <john.stultz@linaro.org>
>> Cc: Sumit Semwal <sumit.semwal@linaro.org>
>> Signed-off-by: Colin Cross <ccross@android.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@linaro.org>
>> ---
>>  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?

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

[Kiran Raparthy]

Hi Jason,

On 27 November 2014 at 15:19, Daniel Thompson
<daniel.thompson@linaro.org> wrote:
> On 26/11/14 17:45, Colin Cross wrote:
>> On Wed, Nov 26, 2014 at 1:14 AM, Kiran Raparthy <kiran.kumar@linaro.org> wrote:
>>> From: Colin Cross <ccross@android.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@windriver.com>
>>> Cc: kgdb-bugreport@lists.sourceforge.net
>>> Cc: linux-kernel@vger.kernel.org
>>> Cc: Android Kernel Team <kernel-team@android.com>
>>> Cc: John Stultz <john.stultz@linaro.org>
>>> Cc: Sumit Semwal <sumit.semwal@linaro.org>
>>> Signed-off-by: Colin Cross <ccross@android.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@linaro.org>
>>> ---
>>>  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?
Regards,
Kiran

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

[Kiran Raparthy]

Hi Jason,

On 1 December 2014 at 11:32, Kiran Raparthy <kiran.kumar@linaro.org> wrote:
> Hi Jason,
>
> On 27 November 2014 at 15:19, Daniel Thompson
> <daniel.thompson@linaro.org> wrote:
>> On 26/11/14 17:45, Colin Cross wrote:
>>> On Wed, Nov 26, 2014 at 1:14 AM, Kiran Raparthy <kiran.kumar@linaro.org> wrote:
>>>> From: Colin Cross <ccross@android.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@windriver.com>
>>>> Cc: kgdb-bugreport@lists.sourceforge.net
>>>> Cc: linux-kernel@vger.kernel.org
>>>> Cc: Android Kernel Team <kernel-team@android.com>
>>>> Cc: John Stultz <john.stultz@linaro.org>
>>>> Cc: Sumit Semwal <sumit.semwal@linaro.org>
>>>> Signed-off-by: Colin Cross <ccross@android.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@linaro.org>
>>>> ---
>>>>  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

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

[Colin Cross]

On Thu, Nov 27, 2014 at 1:49 AM, Daniel Thompson
<daniel.thompson@linaro.org> wrote:
> On 26/11/14 17:45, Colin Cross wrote:
>> 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?

OK, works for me.