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SubjectRe: [PATCH 1/2] printk: Add an option to flush all messages on panic
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On 4/1/2019 4:18 PM, Feng Tang wrote:
> Current console_flush_on_panic() will only dump the new messages
> in buffer, and users may need an opportunity to check all the
> messages on panic which could help debugging, as user may haven't
> seen the log before panic due to loglevel settings.
>
> Add a flag for console_flush_on_panic() to chose whether to
> dump all messages.
>
> Signed-off-by: Feng Tang <feng.tang@intel.com>


Looks good to me.


But, Will it not be good if put it under a config and not change the
prototype, as it is a debug feature?

Thanks,
Mukesh

> ---
> arch/powerpc/kernel/traps.c | 2 +-
> include/linux/console.h | 2 +-
> kernel/panic.c | 2 +-
> kernel/printk/printk.c | 9 ++++++++-
> 4 files changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index 1fd45a8..58d9580 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -179,7 +179,7 @@ extern void panic_flush_kmsg_end(void)
> kmsg_dump(KMSG_DUMP_PANIC);
> bust_spinlocks(0);
> debug_locks_off();
> - console_flush_on_panic();
> + console_flush_on_panic(false);
> }
>
> static unsigned long oops_begin(struct pt_regs *regs)
> diff --git a/include/linux/console.h b/include/linux/console.h
> index ec9bdb3..825ecf5 100644
> --- a/include/linux/console.h
> +++ b/include/linux/console.h
> @@ -175,7 +175,7 @@ extern int console_trylock(void);
> extern void console_unlock(void);
> extern void console_conditional_schedule(void);
> extern void console_unblank(void);
> -extern void console_flush_on_panic(void);
> +extern void console_flush_on_panic(bool flush_all);
> extern struct tty_driver *console_device(int *);
> extern void console_stop(struct console *);
> extern void console_start(struct console *);
> diff --git a/kernel/panic.c b/kernel/panic.c
> index 0ae0d73..fb77e01 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -277,7 +277,7 @@ void panic(const char *fmt, ...)
> * panic() is not being callled from OOPS.
> */
> debug_locks_off();
> - console_flush_on_panic();
> + console_flush_on_panic(false);
>
> panic_print_sys_info();
>
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 02ca827..8ff099b 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2525,10 +2525,11 @@ void console_unblank(void)
>
> /**
> * console_flush_on_panic - flush console content on panic
> + * @flush_all: whether to print all messages in buffer
> *
> * Immediately output all pending messages no matter what.
> */
> -void console_flush_on_panic(void)
> +void console_flush_on_panic(bool flush_all)
> {
> /*
> * If someone else is holding the console lock, trylock will fail
> @@ -2539,6 +2540,12 @@ void console_flush_on_panic(void)
> */
> console_trylock();
> console_may_schedule = 0;
> +
> + /* User may want to see all the printk messages on panic */
> + if (flush_all) {
> + console_seq = log_first_seq;
> + console_idx = log_first_idx;
> + }
> console_unlock();
> }
>

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