Re: [PATCH v5 3/3] arm64/fpsimd: Don't disable softirq when touching FPSIMD/SVE state

[Catalin Marinas]

On Mon, Jun 03, 2019 at 05:25:34PM +0100, Catalin Marinas wrote:
> On Tue, May 21, 2019 at 06:21:39PM +0100, Julien Grall wrote:
> > Since a softirq is supposed to check may_use_simd() anyway before
> > attempting to use FPSIMD/SVE, there is limited reason to keep softirq
> > disabled when touching the FPSIMD/SVE context. Instead, we can simply
> > disable preemption and mark the FPSIMD/SVE context as in use by setting
> > CPU's fpsimd_context_busy flag.
> [...]
> > +static void get_cpu_fpsimd_context(void)
> > +{
> > +	preempt_disable();
> > +	__get_cpu_fpsimd_context();
> > +}
> 
> Is there anything that prevents a softirq being invoked between
> preempt_disable() and __get_cpu_fpsimd_context()?

Actually, it shouldn't matter as the softirq finishes using the fpsimd
before the thread is resumed.

-- 
Catalin