On 28/01/15 10:39, Kiran Raparthy wrote:
> From: Colin Cross <ccr...@android.com>
>
> 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 <jason.wes...@windriver.com>
> Cc: Andrew Morton <a...@linux-foundation.org>
> Cc: kgdb-bugrep...@lists.sourceforge.net
> Cc: linux-kernel@vger.kernel.org
> Cc: Android Kernel Team <kernel-t...@android.com>
> Cc: John Stultz <john.stu...@linaro.org>
> Cc: Sumit Semwal <sumit.sem...@linaro.org>
> Signed-off-by: Colin Cross <ccr...@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
> Modified the commit as per community feedback]
> Signed-off-by: Kiran Raparthy <kiran.ku...@linaro.org>
> Reviewed-by: Daniel Thompson <daniel.thomp...@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();
>
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