linux-kernel - Re: [PATCH 2/2] MIPS: Force CPUs to lose FP context during mode switches

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Message-ID: <alpine.DEB.2.00.1604221700250.21846@tp.orcam.me.uk>
Date:	Fri, 22 Apr 2016 17:06:05 +0100
From:	"Maciej W. Rozycki" <macro@...tec.com>
To:	Paul Burton <paul.burton@...tec.com>
CC:	<linux-mips@...ux-mips.org>, Ralf Baechle <ralf@...ux-mips.org>,
	"stable # v4 . 0+" <stable@...r.kernel.org>,
	Adam Buchbinder <adam.buchbinder@...il.com>,
	<linux-kernel@...r.kernel.org>,
	James Hogan <james.hogan@...tec.com>
Subject: Re: [PATCH 2/2] MIPS: Force CPUs to lose FP context during mode
 switches

On Thu, 21 Apr 2016, Paul Burton wrote:

> Fix this by broadcasting an IPI if other CPUs may have live FP context
> for an affected thread, with a handler causing those CPUs to relinquish
> their FPU ownership. Threads will then be allowed to continue running
> but will stall on the wait_on_atomic_t in enable_restore_fp_context if
> they attempt to use FP again whilst the mode switch is still in
> progress. The end result is less fragile poking at scheduler context
> switch counts & a more expedient completion of the mode switch.

Reviewed-by: Maciej W. Rozycki <macro@...tec.com>

 Thanks, Paul, for your work on this problem!  I'll rebase my outstanding 
NaN interlinking stuff (https://patchwork.linux-mips.org/patch/11491/) on 
top of your patches -- they address the concern expressed there.

  Maciej