linux-kernel - Re: [PATCH v2 4/4] x86/fpu: don't abuse drop_init_fpu() in flush

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Message-ID: <20150314105502.GB3114@pd.tnic>
Date:	Sat, 14 Mar 2015 11:55:02 +0100
From:	Borislav Petkov <bp@...e.de>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Dave Hansen <dave.hansen@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pekka Riikonen <priikone@....fi>,
	Rik van Riel <riel@...hat.com>,
	Suresh Siddha <sbsiddha@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>
Subject: Re: [PATCH v2 4/4] x86/fpu: don't abuse drop_init_fpu() in
 flush_thread()

On Fri, Mar 13, 2015 at 06:30:30PM +0100, Oleg Nesterov wrote:
> flush_thread() -> drop_init_fpu() is suboptimal and confusing. It does
> drop_fpu() or restore_init_xstate() depending on !use_eager_fpu(). But
> flush_thread() too checks eagerfpu right after that, and if it is true
> then restore_init_xstate() just burns CPU for no reason. We are going to
> load init_xstate_buf again after we set used_math/user_has_fpu, until
> then the FPU state can't survive after switch_to().
> 
> Remove it, and change the "if (!use_eager_fpu())" to call drop_fpu().
> While at it, clean up the tsk/current usage.
> 
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Thanks, applied.

Did a trivial cleanup ontop, see reply to this message.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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