linux-kernel - Re: [PATCH x86/mm] x86_64 save_i387

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Date:	Sat, 12 Jan 2008 07:59:21 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Valdis.Kletnieks@...edu
Cc:	Roland McGrath <roland@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH x86/mm] x86_64 save_i387_ia32 snafu


* Valdis.Kletnieks@...edu <Valdis.Kletnieks@...edu> wrote:

> On Fri, 11 Jan 2008 13:31:47 PST, Roland McGrath said:
> > > thanks, applied. Does this explain the crash/hang problems with 32-bit 
> > > apps on 64-bit kernels? What was the exact failure mode?
> > 
> > It does.  Any 32-bit process trying to run a signal handler when it had
> > used the FPU, would clobber "current" with FP bits.  The observed failure
> > mode was shortly after this in the signal handler setup code, when it
> > crashed due to current->mm being zero (current->pid also being zero, and
> > the whole first 512 bytes of the task_struct being garbage).
> 
> For what it's worth, this patch fixes a problem I had in 24-rc6-mm1 
> with kernel panics when certain X programs exited (Eterm being the 
> biggest cause), that I had bisected to "somewhere in 
> git-x86.patch"....

ok, good. Yesterday's x86.git update has this fix included so the next 
-mm iteration should have the fix as well.

	Ingo
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