Hi Jason, On 27 November 2014 at 15:19, Daniel Thompson <[email protected]> wrote: > On 26/11/14 17:45, Colin Cross wrote: >> On Wed, Nov 26, 2014 at 1:14 AM, Kiran Raparthy <[email protected]> >> wrote: >>> From: Colin Cross <[email protected]> >>> >>> 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 <[email protected]> >>> Cc: [email protected] >>> Cc: [email protected] >>> Cc: Android Kernel Team <[email protected]> >>> Cc: John Stultz <[email protected]> >>> Cc: Sumit Semwal <[email protected]> >>> Signed-off-by: Colin Cross <[email protected]> >>> [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 <[email protected]> >>> --- >>> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
