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References: <alpine.LFD.2.02.1202191412060.3898@i5.linux-foundation.org>
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From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Sun, 19 Feb 2012 17:11:12 -0800
Message-ID: <CA+55aFwc6u6Mr9iCMKM+MexfKso4tN7D2VdWpJpuT2saj0Pgfw@mail.gmail.com>
Subject: Re: [PATCH 0/2] More i387 state save/restore work
To: Michael Neuling <mikey@neuling.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        benh@kernel.crashing.org, anton@samba.org
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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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