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[03/27] x86/fpu: Remove preempt_disable() in fpu__clear()

Message ID 20190403164156.19645-4-bigeasy@linutronix.de (mailing list archive)
State New, archived
Headers show
Series [01/27] x86/fpu: Remove fpu->initialized usage in __fpu__restore_sig() | expand

Commit Message

Sebastian Andrzej Siewior April 3, 2019, 4:41 p.m. UTC 
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 registers 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 registers 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>
Reviewed-by: Borislav Petkov <bp@suse.de>
---
 arch/x86/kernel/fpu/core.c | 2 --
 1 file changed, 2 deletions(-)
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Patch

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();
 	}
 }