linux-kernel - Re: [PATCH 0/2] More i387 state save/restore work

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Message-ID: <CA+55aFwc6u6Mr9iCMKM+MexfKso4tN7D2VdWpJpuT2saj0Pgfw@mail.gmail.com>
Date:	Sun, 19 Feb 2012 17:11:12 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Michael Neuling <mikey@...ling.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	benh@...nel.crashing.org, anton@...ba.org
Subject: Re: [PATCH 0/2] More i387 state save/restore work

Oh, and final comment - looking at the thing you pointed at, it looks
much more adventurous than my x86 FP state thing.

I always save things unconditionally, so that I don't have to do the
IPI or just in general care about the "oops, now I want things in
memory, not in some random CPU FP state". So mine is just a "writeback
cache", and only optimizes the reading things back: there is never any
dirty state in the CPU except when the process is actively using it.

That obviously does mean that I only optimize away the restore side,
not the save side. But it's *way* simpler, and considering that I just
spent almost a week trying to figure out FP state save bugs, simple is
good.

                  Linus
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