linux-kernel - Re: [PATCH 05/50] arm: Add loglvl to unwind

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Message-ID: <cd6c5df5-effd-a1f9-8a25-9f5aac3a92f9@arista.com>
Date:   Wed, 6 Nov 2019 16:32:07 +0000
From:   Dmitry Safonov <dima@...sta.com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     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>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH 05/50] arm: Add loglvl to unwind_backtrace()

On 11/6/19 9:12 AM, Russell King - ARM Linux admin wrote:
> On Wed, Nov 06, 2019 at 03:04:56AM +0000, Dmitry Safonov wrote:
>> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
>> index 7c3f32b26585..69e35462c9e9 100644
>> --- a/arch/arm/kernel/traps.c
>> +++ b/arch/arm/kernel/traps.c
>> @@ -202,7 +202,7 @@ static void dump_instr(const char *lvl, struct pt_regs *regs)
>>  #ifdef CONFIG_ARM_UNWIND
>>  static inline void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
>>  {
>> -	unwind_backtrace(regs, tsk);
>> +	unwind_backtrace(regs, tsk, KERN_DEBUG);
> 
> Why demote this to debug level?  This is used as part of the kernel
> panic message, surely we don't want this at debug level?  What about
> the non-unwind version?

Right, I wanted to keep the old loglevel in this patch - KERN_DEFAULT.
But got confused with log level in unwind_backtrace().
Will fix.

[..]
>> diff --git a/arch/arm/kernel/unwind.c b/arch/arm/kernel/unwind.c
>> index 0a65005e10f0..caaae1b6f721 100644
>> --- a/arch/arm/kernel/unwind.c
>> +++ b/arch/arm/kernel/unwind.c
>> @@ -455,11 +455,12 @@ int unwind_frame(struct stackframe *frame)
>>  	return URC_OK;
>>  }
>>  
>> -void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk)
>> +void unwind_backtrace(struct pt_regs *regs, struct task_struct *tsk,
>> +		      const char *loglvl)
>>  {
>>  	struct stackframe frame;
>>  
>> -	pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
>> +	printk("%s%s(regs = %p tsk = %p)\n", loglvl, __func__, regs, tsk);
> 
> Clearly, this isn't supposed to be part of the normal backtrace output...

Yes, sorry it's debug for a backtrace - will return pr_debug() for the
message.

Thanks,
          Dmitry