linux-kernel - [tip: x86/fpu] x86/fpu: Simplify fpregs

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Date:   Wed, 11 Nov 2020 13:36:24 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/fpu] x86/fpu: Simplify fpregs_[un]lock()

The following commit has been merged into the x86/fpu branch of tip:

Commit-ID:     5f0c71278d6848b4809f83af90f28196e1505ab1
Gitweb:        https://git.kernel.org/tip/5f0c71278d6848b4809f83af90f28196e1505ab1
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Tue, 27 Oct 2020 11:09:50 +01:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Wed, 11 Nov 2020 14:35:16 +01:00

x86/fpu: Simplify fpregs_[un]lock()

There is no point in disabling preemption and then disabling bottom
halfs.

Just disabling bottom halfs is sufficient as it implicitly disables
preemption on !RT kernels.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Link: https://lore.kernel.org/r/20201027101349.455380473@linutronix.de

---
 arch/x86/include/asm/fpu/api.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h
index dcd9503..2c5bef7 100644
--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -29,17 +29,18 @@ extern void fpregs_mark_activate(void);
  * A context switch will (and softirq might) save CPU's FPU registers to
  * fpu->state and set TIF_NEED_FPU_LOAD leaving CPU's FPU registers in
  * a random state.
+ *
+ * local_bh_disable() protects against both preemption and soft interrupts
+ * on !RT kernels.
  */
 static inline void fpregs_lock(void)
 {
-	preempt_disable();
 	local_bh_disable();
 }
 
 static inline void fpregs_unlock(void)
 {
 	local_bh_enable();
-	preempt_enable();
 }
 
 #ifdef CONFIG_X86_DEBUG_FPU