linux-kernel - Re: math_state_restore and kernel_fpu

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Message-ID: <20140121135854.GE21195@quack.suse.cz>
Date:	Tue, 21 Jan 2014 14:58:54 +0100
From:	Jan Kara <jack@...e.cz>
To:	Nate Eldredge <nate@...tsmathematics.com>
Cc:	George Spelvin <linux@...izon.com>, adilger@...ger.ca,
	arjan@...ux.intel.com, jack@...e.cz, linux-kernel@...r.kernel.org,
	maarten-baert@...mail.com, mingo@...e.hu,
	suresh.b.siddha@...el.com, tglx@...utronix.de,
	viro@...iv.linux.org.uk
Subject: Re: math_state_restore and kernel_fpu_end disable interrupts?

On Mon 20-01-14 19:22:51, Nate Eldredge wrote:
> On Sun, 19 Jan 2014, George Spelvin wrote:
> 
> >>It's credited to Suresh Siddha, whom I've cc'ed (along with others who
> >>signed off).  Suresh, if you're still around, could you comment on why
> >>math_state_restore always leaves interrupts disabled, regardless of their
> >>state on entry?  Is there a deep reason or is it a bug?
> >
> >What the comments seemed to be implying was that it was a bug to enter
> >this code with interrupts enabled.  So the problem may be a little bit
> >more systemic; expert counsel is required.
> 
> It would be kind of weird for code that requires disabled interrupts
> on entry to turn around and enable interrupts itself.  I agree that
> it would really help for a guru to take a look...
> 
> On which note, Suresh's email bounced :-(
  Guys, since this is lurking without proper attention for a rather long
time, can you just write a patch which fixes the problem as far as you can
tell, test that the patch indeed fixes your problems and if yes, send it
to Ingo & LKML. If nothing else it should get you more attention.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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