linux-kernel - Re: [PATCH] print kdump kernel loaded status in stack dump

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Date:   Fri, 19 Jan 2018 17:28:35 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Dave Young <dyoung@...hat.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Andi Kleen <ak@...ux.intel.com>, pmladek@...e.com,
        sergey.senozhatsky@...il.com, rostedt@...dmis.org,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        kexec@...ts.infradead.org
Subject: Re: [PATCH] print kdump kernel loaded status in stack dump

On (01/19/18 16:16), Dave Young wrote:
> On 01/19/18 at 02:45pm, Sergey Senozhatsky wrote:
> > On (01/18/18 10:02), Andi Kleen wrote:
> > > Dave Young <dyoung@...hat.com> writes:
> > > >  		printk("%sHardware name: %s\n",
> > > >  		       log_lvl, dump_stack_arch_desc_str);
> > > > +	if (kexec_crash_loaded())
> > > > +		printk("%skdump kernel loaded\n", log_lvl);
> > > 
> > > Oops/warnings are getting longer and longer, often scrolling away
> > > from the screen, and if the kernel crashes backscroll does not work
> > > anymore, so precious information is lost.
> > 
> > true. I even ended up having a console_reflush_on_panic() function. it
> > simply re-prints with a delay [so I can at least read the oops] logbuf
> > entries every once in a while, staring with the first oops_in_progress
> > record.
> > 
> 
> If too many messages printed on screen, then the next flush will 
> still scroll up. 

right. but it re-prints Oops with a new console_unlock_delay() delay
which gives me enough time to either read it as many times as I want,
or take a picture, etc. it's not as fast as the normal oops print out.

[I'm not entirely sure I see why do we have printk_delay() in
   vprintk_emit()... I mean I probably can see some reasoning behind
   it, but at the same it makes sense to slow down console_unlock()
   as well]

	-ss