From: Petr Mladek <pmladek@suse.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Feng Tang <feng.tang@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org, Kees Cook <keescook@chromium.org>,
Borislav Petkov <bp@suse.de>,
ying.huang@intel.com
Subject: Re: [PATCH v2] panic: add an option to replay all the printk message in buffer
Date: Wed, 17 Apr 2019 14:24:58 +0200 [thread overview]
Message-ID: <20190417122458.mhl3orevzha7sp6h@pathway.suse.cz> (raw)
In-Reply-To: <20190417105010.GA8492@jagdpanzerIV>
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;
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.
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
next prev parent reply other threads:[~2019-04-17 12:25 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-10 15:37 [PATCH v2] panic: add an option to replay all the printk message in buffer Feng Tang
2019-04-17 4:19 ` Andrew Morton
2019-04-17 6:48 ` Feng Tang
2019-04-17 9:18 ` Petr Mladek
2019-04-17 9:46 ` Sergey Senozhatsky
2019-04-17 10:50 ` Sergey Senozhatsky
2019-04-17 12:24 ` Petr Mladek [this message]
2019-04-17 15:18 ` Feng Tang
2019-04-18 0:00 ` Sergey Senozhatsky
2019-04-18 7:45 ` Petr Mladek
2019-04-18 9:00 ` Feng Tang
2019-04-18 11:01 ` Petr Mladek
2019-04-19 2:08 ` Feng Tang
2019-04-18 10:50 ` Sergey Senozhatsky
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