Messages in this thread | | | Date | Wed, 17 Apr 2019 23:18:17 +0800 | From | Feng Tang <> | Subject | Re: [PATCH v2] panic: add an option to replay all the printk message in buffer |
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On Wed, Apr 17, 2019 at 02:24:58PM +0200, Petr Mladek wrote: > On Wed 2019-04-17 19:50:10, Sergey Senozhatsky wrote: > > On (04/17/19 18:46), Sergey Senozhatsky wrote: > > > > > > Does not look too complex/ugly. > > > > Looks simpler than adding one more global state to the > > console_unlock() printing loop. > > > > // Not tested at all // > > > > diff --git a/kernel/panic.c b/kernel/panic.c > > index cd73af35ec66..50eacfc9bc7e 100644 > > --- a/kernel/panic.c > > +++ b/kernel/panic.c > > @@ -51,6 +51,7 @@ EXPORT_SYMBOL_GPL(panic_timeout); > > #define PANIC_PRINT_TIMER_INFO 0x00000004 > > #define PANIC_PRINT_LOCK_INFO 0x00000008 > > #define PANIC_PRINT_FTRACE_INFO 0x00000010 > > +#define PANIC_PRINT_ALL_PRINTK_MSG 0x00000020 > > unsigned long panic_print; > > > > ATOMIC_NOTIFIER_HEAD(panic_notifier_list); > > @@ -148,6 +149,9 @@ static void panic_print_sys_info(void) > > > > if (panic_print & PANIC_PRINT_FTRACE_INFO) > > ftrace_dump(DUMP_ALL); > > + > > + if (panic_print & PANIC_PRINT_ALL_PRINTK_MSG) > > + console_flush_on_panic(CONSOLE_FLUSH_ALL); > > The console must be replayed as the first thing in > panic_print_sys_info(). Otherwise, the original messages > are replaced by the other dumps. Especially ftrace_dump() > might be pretty long. > > Also the names of the function and the parameter are misleading. > All messages are already flushed when this is called. > > > } > > > > /** > > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c > > index 17102fd4c136..da60a185dbbb 100644 > > --- a/kernel/printk/printk.c > > +++ b/kernel/printk/printk.c > > @@ -2549,6 +2549,14 @@ void console_flush_on_panic(void) > > */ > > console_trylock(); > > console_may_schedule = 0; > > + if (flush_mode == CONSOLE_FLUSH_ALL) { > > + /* > > + * Can be done under logbuf lock, but it's unlikely that > > + * we will have any race conditions here. > > + */ > > + console_seq = log_first_seq; > > + console_idx = log_first_idx;
This is very similar to my V1 patch :), excepted I used a bool as the parameter.
> > I agree that it is easier. The cost is that the same messages are > printed again without any explanation. > > I still think that it would be convenient to write a header line. > It would help to understand the log for any, even 3rd-party, reader. > Also it would help to find the beginning in a very long log.
My thought is, the replay is only a debug option and disabled by default, so when user specifically enable the bit of PANIC_PRINT_ALL_PRINTK_MSG, the whole replay of printk msg should be expected.
Thanks, Feng
> > If the complexity of console_unlock() is the concern, we could > refactor the code, e.g. put this "reset log" code into a separate > function. > > Best Regards, > Petr
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