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From: Ingo Molnar <mingo@kernel.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	"H. Peter Anvin" <hpa@zytor.com>, Dave Jones <davej@redhat.com>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: scheduling while atomic & hang.
Date: Sat, 6 Jul 2013 10:07:44 +0200	[thread overview]
Message-ID: <20130706080744.GA1342@gmail.com> (raw)
In-Reply-To: <20130706080225.GA439@somewhere>


* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> On Fri, Jul 05, 2013 at 12:27:51PM -0700, Linus Torvalds wrote:
> > On Thu, Jul 4, 2013 at 11:51 PM, Ingo Molnar <mingo@kernel.org> wrote:
> > >
> > > It would be nice to have a full-kernel-stack backtrace printout as an
> > > option, which prints entries 'above' the current RSP.
> > 
> > One problem with that is that it is likely to be mostly overwritten by 
> > the debug code that is about to print this all out - and any non-debug 
> > code may well be really old, just with a sufficiently deep stack trace 
> > to show up. Not to mention missing any irq-stack changes etc anyway.
> > 
> > So it can easily be *very* misleading - I'm not sure how useful it 
> > would be as an idea.
> > 
> >                 Linus
> 
> So if the unwider doesn't run with the same stak than the target, it 
> migh work. This can work with BUG for example But I believe that WARN 
> doesn't do a trap in x86.

Instead of switching stacks it might be better to create an early snapshot 
of the stack into a temporary area before calling anything, and to print 
that. This is debug code, so overhead is not a big issue.

But yeah, Linus is right, it gets hairy, can be misleading and has limited 
utility :-/

Thanks,

	Ingo

  reply	other threads:[~2013-07-06  8:07 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-04  1:55 scheduling while atomic & hang Dave Jones
2013-07-04  2:49 ` Linus Torvalds
2013-07-04  4:43   ` H. Peter Anvin
2013-07-04  7:49   ` Dave Jones
2013-07-04 17:22     ` Linus Torvalds
2013-07-10 20:54     ` J. Bruce Fields
2013-07-04 18:08   ` H. Peter Anvin
2013-07-05  6:51     ` Ingo Molnar
2013-07-05  7:19       ` Frederic Weisbecker
2013-07-05 10:05         ` Ingo Molnar
2013-07-05 19:27       ` Linus Torvalds
2013-07-06  8:02         ` Frederic Weisbecker
2013-07-06  8:07           ` Ingo Molnar [this message]
2013-07-05 14:38   ` Yet more softlockups Dave Jones
2013-07-05 15:15     ` Thomas Gleixner
2013-07-05 16:00       ` Dave Jones
2013-07-05 16:02         ` Thomas Gleixner
2013-07-05 16:41           ` H. Peter Anvin
2013-07-05 18:20             ` Seiji Aguchi
2013-07-05 22:21               ` Thomas Gleixner
2013-07-06  7:24         ` Ingo Molnar
2013-07-07  0:24           ` Dave Jones
2013-07-10 15:13           ` Dave Jones
2013-07-10 15:20             ` Markus Trippelsdorf
2013-07-10 15:40               ` Dave Jones
2013-07-12 10:31                 ` Ingo Molnar
2013-07-12 15:38                   ` Dave Hansen
2013-07-12 15:45                     ` Dave Jones
2013-07-12 15:55                       ` Dave Hansen
2013-07-12 17:00                         ` Dave Jones
2013-07-12 17:12                       ` David Ahern
2013-07-12 17:18                         ` Dave Jones
2013-07-12 17:40                           ` David Ahern
2013-07-12 17:50                             ` Dave Jones
2013-07-12 18:07                               ` David Ahern
2013-07-12 18:22                                 ` Dave Hansen
2013-07-12 20:13                                 ` Dave Hansen
2013-07-13  1:40                       ` Vince Weaver
2013-07-10 15:39             ` Vince Weaver
2013-07-10 15:45               ` Dave Jones
2013-07-10 21:54               ` Dave Jones

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