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From:   Alexander Potapenko <glider@google.com>
Date:   Wed, 5 May 2021 12:58:17 +0200
Message-ID: <CAG_fn=UTGBzwNWG92yUk4v-2=kFayYuUO+XfaJ5J4RnOESx-NA@mail.gmail.com>
Subject: Re: [PATCH 1/2] printk: introduce dump_stack_lvl()
To:     Marco Elver <elver@google.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Petr Mladek <pmladek@suse.com>, Ingo Molnar <mingo@kernel.org>,
        bo.he@intel.com, yanmin_zhang@linux.intel.com,
        psodagud@quicinc.com, Dmitry Vyukov <dvyukov@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>, he@google.com
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On Wed, May 5, 2021 at 12:37 PM Marco Elver <elver@google.com> wrote:
>
> On Wed, 5 May 2021 at 11:22, Alexander Potapenko <glider@google.com> wrote:
> > dump_stack() is used for many different cases, which may require a log
> > level consistent with other kernel messages surrounding the dump_stack()
> > call.
> > Without that, certain systems that are configured to ignore the default
> > level messages will miss stack traces in critical error reports.
> >
> > This patch introduces dump_stack_lvl() that behaves similarly to
> > dump_stack(), but accepts a custom log level.
> > The old dump_stack() becomes equal to dump_stack_lvl(KERN_DEFAULT).
> >
> > A somewhat similar patch has been proposed in 2012:
> > https://lore.kernel.org/lkml/1332493269.2359.9.camel@hebo/
> > , but wasn't merged.
> >
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Petr Mladek <pmladek@suse.com>
> > Cc: Ingo Molnar <mingo@kernel.org>
> > Cc: he, bo <bo.he@intel.com>
> > Cc: Yanmin Zhang <yanmin_zhang@linux.intel.com>
> > Cc: Prasad Sodagudi <psodagud@quicinc.com>
> > Cc: Dmitry Vyukov <dvyukov@google.com>
> > Cc: Marco Elver <elver@google.com>
> > Cc: linux-kernel@vger.kernel.org
> > Signed-off-by: Alexander Potapenko <glider@google.com>
> > ---
> >  include/linux/printk.h |  1 +
> >  lib/dump_stack.c       | 19 ++++++++++++-------
> >  2 files changed, 13 insertions(+), 7 deletions(-)
> >
> > diff --git a/include/linux/printk.h b/include/linux/printk.h
> > index fe7eb2351610..abe274305d79 100644
> > --- a/include/linux/printk.h
> > +++ b/include/linux/printk.h
> > @@ -206,6 +206,7 @@ void __init setup_log_buf(int early);
> >  __printf(1, 2) void dump_stack_set_arch_desc(const char *fmt, ...);
> >  void dump_stack_print_info(const char *log_lvl);
> >  void show_regs_print_info(const char *log_lvl);
> > +extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold;
> >  extern asmlinkage void dump_stack(void) __cold;
> >  extern void printk_safe_flush(void);
> >  extern void printk_safe_flush_on_panic(void);
> > diff --git a/lib/dump_stack.c b/lib/dump_stack.c
> > index f5a33b6f773f..3d2c324a4929 100644
> > --- a/lib/dump_stack.c
> > +++ b/lib/dump_stack.c
> > @@ -73,10 +73,10 @@ void show_regs_print_info(const char *log_lvl)
> >         dump_stack_print_info(log_lvl);
> >  }
> >
> > -static void __dump_stack(void)
> > +static void __dump_stack(const char *log_lvl)
> >  {
> > -       dump_stack_print_info(KERN_DEFAULT);
> > -       show_stack(NULL, NULL, KERN_DEFAULT);
> > +       dump_stack_print_info(log_lvl);
> > +       show_stack(NULL, NULL, log_lvl);
> >  }
> >
> >  /**
> > @@ -87,7 +87,7 @@ static void __dump_stack(void)
> >  #ifdef CONFIG_SMP
> >  static atomic_t dump_lock = ATOMIC_INIT(-1);
> >
> > -asmlinkage __visible void dump_stack(void)
> > +asmlinkage __visible void dump_stack_lvl(const char *log_lvl)
> >  {
> >         unsigned long flags;
> >         int was_locked;
> > @@ -117,7 +117,7 @@ asmlinkage __visible void dump_stack(void)
> >                 goto retry;
> >         }
> >
> > -       __dump_stack();
> > +       __dump_stack(log_lvl);
> >
> >         if (!was_locked)
> >                 atomic_set(&dump_lock, -1);
> > @@ -125,9 +125,14 @@ asmlinkage __visible void dump_stack(void)
> >         local_irq_restore(flags);
> >  }
> >  #else
> > -asmlinkage __visible void dump_stack(void)
> > +asmlinkage __visible void dump_stack_lvl(const char *log_lvl)
> >  {
> > -       __dump_stack();
> > +       __dump_stack(log_lvl);
> >  }
> >  #endif
>
> +EXPORT_SYMBOL(dump_stack_lvl);
>
> is missing here?

You are right, will fix in v2.