linux-kernel - Re: [PATCH] Documentation/livepatch: remove the limitation for schedule() patching

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Message-ID: <alpine.LSU.2.20.1701101131510.28763@pobox.suse.cz>
Date:   Tue, 10 Jan 2017 11:32:12 +0100 (CET)
From:   Miroslav Benes <mbenes@...e.cz>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
cc:     jeyu@...hat.com, jikos@...nel.org, pmladek@...e.com,
        corbet@....net, live-patching@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Documentation/livepatch: remove the limitation for
 schedule() patching

On Mon, 9 Jan 2017, Josh Poimboeuf wrote:

> On Mon, Jan 09, 2017 at 01:50:19PM +0100, Miroslav Benes wrote:
> > There is still one thing which I don't understand. Why __schedule() 
> > (patched or the original) is not on the stack. The actual "sleep" 
> > should happen in __switch_to_asm() which is C function now. And there is a 
> > call to __switch_to_asm() in __schedule(). __schedule() thus should be on 
> > the stack, shouldn't it? What am I missing? __switch_to_asm() pushes %rbp 
> > on the stack...
> 
> Ah, this is an unwinder bug.  get_frame_pointer() needs to be fixed so
> that for an inactive task it returns a pointer to inactive_task_frame.bp
> rather than the value of inactive_task_frame.bp itself.  Will fix it.

And it works with the fix. Thanks.

Miroslav