diff options
Diffstat (limited to 'arch/x86/include/asm/fpu/api.h')
| -rw-r--r-- | arch/x86/include/asm/fpu/api.h | 17 |
1 files changed, 7 insertions, 10 deletions
diff --git a/arch/x86/include/asm/fpu/api.h b/arch/x86/include/asm/fpu/api.h index f86ad3335529..f42de5f05e7e 100644 --- a/arch/x86/include/asm/fpu/api.h +++ b/arch/x86/include/asm/fpu/api.h @@ -16,10 +16,9 @@ /* * Use kernel_fpu_begin/end() if you intend to use FPU in kernel context. It - * disables preemption so be careful if you intend to use it for long periods - * of time. - * If you intend to use the FPU in irq/softirq you need to check first with - * irq_fpu_usable() if it is possible. + * disables preemption and softirq processing, so be careful if you intend to + * use it for long periods of time. Kernel-mode FPU cannot be used in all + * contexts -- see irq_fpu_usable() for details. */ /* Kernel FPU states to initialize in kernel_fpu_begin_mask() */ @@ -50,10 +49,10 @@ static inline void kernel_fpu_begin(void) } /* - * Use fpregs_lock() while editing CPU's FPU registers or fpu->fpstate. - * A context switch will (and softirq might) save CPU's FPU registers to - * fpu->fpstate.regs and set TIF_NEED_FPU_LOAD leaving CPU's FPU registers in - * a random state. + * Use fpregs_lock() while editing CPU's FPU registers or fpu->fpstate, or while + * using the FPU in kernel mode. A context switch will (and softirq might) save + * CPU's FPU registers to fpu->fpstate.regs 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. @@ -63,8 +62,6 @@ static inline void kernel_fpu_begin(void) * 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) { |