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author | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-15 05:47:38 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-12-15 05:47:38 +0300 |
commit | eb0ea74120e0f14a6d6454109153d1b4ccf210fc (patch) | |
tree | fa50e040a5507cfeed1a37514cffc6f020eb3bbb /arch/x86 | |
parent | edd7ab76847442e299af64a761febd180d71f98d (diff) | |
parent | cba08c5dc6dc1a906a0b5ddac9a9ac6c9a64f2e8 (diff) | |
download | linux-eb0ea74120e0f14a6d6454109153d1b4ccf210fc.tar.xz |
Merge tag 'x86-fpu-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 FPU updates from Thomas Gleixner:
- Simplify the FPU protection for !RT kernels
- Add the RT variant of FPU protections
* tag 'x86-fpu-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/fpu: Make kernel FPU protection RT friendly
x86/fpu: Simplify fpregs_[un]lock()
Diffstat (limited to 'arch/x86')
-rw-r--r-- | arch/x86/include/asm/fpu/api.h | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h index dcd9503b1098..a5aba4ab0224 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -29,17 +29,32 @@ 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. + * + * On RT kernels local_bh_disable() is not sufficient because it only + * serializes soft interrupt related sections via a local lock, but stays + * preemptible. Disabling preemption is the right choice here as bottom + * half processing is always in thread context on RT kernels so it + * implicitly prevents bottom half processing as well. + * + * Disabling preemption also serializes against kernel_fpu_begin(). */ static inline void fpregs_lock(void) { - preempt_disable(); - local_bh_disable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_bh_disable(); + else + preempt_disable(); } static inline void fpregs_unlock(void) { - local_bh_enable(); - preempt_enable(); + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) + local_bh_enable(); + else + preempt_enable(); } #ifdef CONFIG_X86_DEBUG_FPU |