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Message-ID: <CAMo8Bf+q0j81VZeUQdvCkXt131uzSBfJ0N7RTe7+NpjRkVpzdA@mail.gmail.com>
Date: Tue, 5 Nov 2019 20:13:22 -0800
From: Max Filippov <jcmvbkbc@...il.com>
To: Dmitry Safonov <dima@...sta.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Dmitry Safonov <0x7f454c46@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Ingo Molnar <mingo@...nel.org>, Jiri Slaby <jslaby@...e.com>,
Petr Mladek <pmladek@...e.com>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Steven Rostedt <rostedt@...dmis.org>,
Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
Chris Zankel <chris@...kel.net>,
"open list:TENSILICA XTENSA PORT (xtensa)"
<linux-xtensa@...ux-xtensa.org>
Subject: Re: [PATCH 43/50] xtensa: Add show_stack_loglvl()
Hi Dmitry,
On Tue, Nov 5, 2019 at 7:08 PM Dmitry Safonov <dima@...sta.com> wrote:
>
> Currently, the log-level of show_stack() depends on a platform
> realization. It creates situations where the headers are printed with
> lower log level or higher than the stacktrace (depending on
> a platform or user).
>
> Furthermore, it forces the logic decision from user to an architecture
> side. In result, some users as sysrq/kdb/etc are doing tricks with
> temporary rising console_loglevel while printing their messages.
> And in result it not only may print unwanted messages from other CPUs,
> but also omit printing at all in the unlucky case where the printk()
> was deferred.
>
> Introducing log-level parameter and KERN_UNSUPPRESSED [1] seems
> an easier approach than introducing more printk buffers.
> Also, it will consolidate printings with headers.
>
> Introduce show_stack_loglvl(), that eventually will substitute
> show_stack().
>
> Cc: Chris Zankel <chris@...kel.net>
> Cc: Max Filippov <jcmvbkbc@...il.com>
> Cc: linux-xtensa@...ux-xtensa.org
> [1]: https://lore.kernel.org/lkml/20190528002412.1625-1-dima@arista.com/T/#u
> Signed-off-by: Dmitry Safonov <dima@...sta.com>
> ---
> arch/xtensa/kernel/traps.c | 16 +++++++++++-----
> 1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
> index cbc0d673f542..ba6c150095c6 100644
> --- a/arch/xtensa/kernel/traps.c
> +++ b/arch/xtensa/kernel/traps.c
> @@ -502,7 +502,8 @@ static void show_trace(struct task_struct *task, unsigned long *sp,
>
> static int kstack_depth_to_print = 24;
>
> -void show_stack(struct task_struct *task, unsigned long *sp)
> +void show_stack_loglvl(struct task_struct *task, unsigned long *sp,
> + const char *loglvl)
> {
> int i = 0;
> unsigned long *stack;
> @@ -511,16 +512,21 @@ void show_stack(struct task_struct *task, unsigned long *sp)
> sp = stack_pointer(task);
> stack = sp;
>
> - pr_info("Stack:\n");
> + printk("%sStack:\n", loglvl);
>
> for (i = 0; i < kstack_depth_to_print; i++) {
> if (kstack_end(sp))
> break;
> - pr_cont(" %08lx", *sp++);
> + printk("%s %08lx", loglvl, *sp++);
> if (i % 8 == 7)
> - pr_cont("\n");
> + printk("%s\n", loglvl);
> }
> - show_trace(task, stack, KERN_INFO);
> + show_trace(task, stack, loglvl);
> +}
> +
> +void show_stack(struct task_struct *task, unsigned long *sp)
> +{
> + show_stack_loglvl(task, sp, KERN_INFO);
> }
>
> DEFINE_SPINLOCK(die_lock);
> --
> 2.23.0
This change doesn't work well with printk timestamps, it changes
the following output on xtensa architecture
[ 3.404675] Stack:
[ 3.404861] a05773e2 00000018 bb03dc34 bb03dc30 a0008640 bb03dc70
ba9ba410 37c3f000
[ 3.405414] 37c3f000 d7c3f000 00000800 bb03dc50 a02b97ed bb03dc90
ba9ba400 ba9ba410
[ 3.405969] a05fc1bc bbff28dc 00000000 bb03dc70 a02b7fb9 bb03dce0
ba9ba410 a0579044
into this:
[ 3.056825] Stack:
[ 3.056963] a04ebb20
[ 3.056995] bb03dc10
[ 3.057138] 00000001
[ 3.057277] bb03dc10
[ 3.057815] a00083ca
[ 3.057965] bb03dc50
[ 3.058107] ba9ba410
[ 3.058247] 37c3f000
[ 3.058387]
[ 3.058584] a05773e2
[ 3.058614] 00000001
[ 3.058755] a05ca0bc
[ 3.058896] bb03dc30
[ 3.059035] a000865c
[ 3.059180] bb03dc70
[ 3.059319] ba9ba410
[ 3.059459] 37c3f000
[ 3.059598]
[ 3.059795] 37c3f000
[ 3.059824] d7c3f000
[ 3.059964] 00000800
[ 3.060103] bb03dc50
[ 3.060241] a02b9809
[ 3.060379] bb03dc90
[ 3.060519] ba9ba400
[ 3.060658] ba9ba410
[ 3.060796]
--
Thanks.
-- Max
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