Re: [PATCH 1/2] x86/dumpstack: on oops do not rewind stack for kthread

From	Thomas Gleixner <tglx@linutronix.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/2] x86/dumpstack: on oops do not rewind stack for kthread
Date	2016-10-21 10:10 +0200
Message-ID	<suD3Q-2RW-25@gated-at.bofh.it> (permalink)
References	<sjS6e-2q3-7@gated-at.bofh.it> <suuDg-5F6-13@gated-at.bofh.it> <suB22-1nm-11@gated-at.bofh.it>
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On Fri, 21 Oct 2016, Peter Zijlstra wrote:
> We need to preserve the entire struct kthread on the stack, kthread just
> abuses that pointer to stash an on-stack kthread descriptor. See
> kthread():
> 
>   current->vfork_done = &self.exited;
> 
> Its a horrible horrible thing kthread does. I suppose there might have
> been some intent by keeping that exited completion last in the
> structure, but *shudder*.
> 
> But yes, leaving enough stack to not clobber that might keep this horror
> show working.
> 
> ISTR talk about alternative schemes for this a long time ago, but I
> cannot recall :-(

The simplest solution would be to stick struct kthread into task_struct,
but that's bloat.

But we can allocate it seperately along with kthread_create_info. That's
pretty straight forward.

Thanks,

	tglx

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Re: [PATCH 1/2] x86/dumpstack: on oops do not rewind stack for kthread Andy Lutomirski <luto@amacapital.net> - 2016-10-21 01:10 +0200
  Re: [PATCH 1/2] x86/dumpstack: on oops do not rewind stack for  kthread Peter Zijlstra <peterz@infradead.org> - 2016-10-21 08:00 +0200
    Re: [PATCH 1/2] x86/dumpstack: on oops do not rewind stack for  kthread Thomas Gleixner <tglx@linutronix.de> - 2016-10-21 10:10 +0200

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