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    Subject[PATCH 10/29] x86/fpu: Remove preempt_disable() in fpu__clear()
    Date
    The preempt_disable() section was introduced in commit
    a10b6a16cdad8 ("x86/fpu: Make the fpu state change in fpu__clear() scheduler-atomic")
    and it was said to be temporary.

    fpu__initialize() initializes the FPU struct to its "init" value and
    then sets ->initialized to 1. The last part is the important one.
    The content of the `state' does not matter because it gets set via
    copy_init_fpstate_to_fpregs().
    A preemption here has little meaning because the register will always be
    set to the same content after copy_init_fpstate_to_fpregs(). A softirq
    with a kernel_fpu_begin() could also force to save FPU's register after
    fpu__initialize() without changing the outcome here.

    Remove the preempt_disable() section in fpu__clear(), preemption here
    does not hurt.

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    ---
    arch/x86/kernel/fpu/core.c | 2 --
    1 file changed, 2 deletions(-)

    diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
    index 1d3ae7988f7f2..1940319268aef 100644
    --- a/arch/x86/kernel/fpu/core.c
    +++ b/arch/x86/kernel/fpu/core.c
    @@ -366,11 +366,9 @@ void fpu__clear(struct fpu *fpu)
    * Make sure fpstate is cleared and initialized.
    */
    if (static_cpu_has(X86_FEATURE_FPU)) {
    - preempt_disable();
    fpu__initialize(fpu);
    user_fpu_begin();
    copy_init_fpstate_to_fpregs();
    - preempt_enable();
    }
    }

    --
    2.20.0.rc1
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