Messages in this thread | | | Date | Thu, 15 Jan 2015 21:22:11 -0500 | From | Rik van Riel <> | Subject | Re: [PATCH 1/3] x86, fpu: introduce per-cpu "bool in_kernel_fpu" |
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On 01/15/2015 02:19 PM, Oleg Nesterov wrote: > interrupted_kernel_fpu_idle() tries to detect if > kernel_fpu_begin() is safe or not. In particular it should > obviously deny the nested kernel_fpu_begin() and this logic looks > very confusing. > > If use_eager_fpu() == T we rely on a) __thread_has_fpu() check in > interrupted_kernel_fpu_idle(), and b) on the fact that _begin() > does __thread_clear_has_fpu(). > > Otherwise we demand that the interrupted task has no FPU if it is > in kernel mode, this works because __kernel_fpu_begin() does clts() > and interrupted_kernel_fpu_idle() checks X86_CR0_TS. > > Add the per-cpu "bool in_kernel_fpu" variable, and change this > code to check/set/clear it. This allows to do more cleanups and > fixes, see the next changes. > > The patch also moves WARN_ON_ONCE() under preempt_disable() just > to make this_cpu_read() look better, this is not really needed. And > in fact I think we should move it into __kernel_fpu_begin(). > > Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
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