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Date: Mon, 16 Feb 2015 19:14:17 +0100
From: Oleg Nesterov <oleg@redhat.com>
To: Rik van Riel <riel@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>, dave.hansen@linux.intel.com,
        sbsiddha@gmail.com, luto@amacapital.net, tglx@linutronix.de,
        mingo@kernel.org, hpa@zytor.com, fenghua.yu@intel.com, x86@kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/8] x86, fpu: unlazy_fpu: don't reset
	thread.fpu_counter
Message-ID: <20150216181417.GA7382@redhat.com>
References: <1423252925-14451-1-git-send-email-riel@redhat.com> <1423252925-14451-2-git-send-email-riel@redhat.com> <20150216170433.GF4458@pd.tnic> <54E22FCD.3030202@redhat.com>
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On 02/16, Rik van Riel wrote:
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> On 02/16/2015 12:04 PM, Borislav Petkov wrote:
>
> > ... and so by looking at the unlazy_fpu() call sites, I think this
> > makes sense.
> >
> > So how's that for a commit message instead:
> >
> > --- x86, fpu, unlazy_fpu: Don't reset thread.fpu_counter
> >
> > The "else" branch clears ->fpu_counter as a remnant of the lazy
> > FPU usage counting:
> >
> > e07e23e1fd30 ("[PATCH] non lazy "sleazy" fpu implementation")
> >
> > However, switch_fpu_prepare() does this now so that else branch is
> > superfluous.
> >
> > If we do use_eager_fpu(), then this has no effect. Otherwise, if
> > we actually wanted to prevent fpu preload after the context switch
> > we would need to reset it unconditionally, even if
> > __thread_has_fpu(). ---
> >
> > ?
>
> Good detective work.
>
> Your changelog makes sense to me.

And to me, thanks.

Should I resend?

Oleg.