Commit cb3ea4b7 authored Jan 24, 2023 by Jens Axboe Committed by Ingo Molnar Jan 25, 2023

x86/fpu: Don't set TIF_NEED_FPU_LOAD for PF_IO_WORKER threads



We don't set it on PF_KTHREAD threads as they never return to userspace,
and PF_IO_WORKER threads are identical in that regard. As they keep
running in the kernel until they die, skip setting the FPU flag on them.

More of a cosmetic thing that was found while debugging and
issue and pondering why the FPU flag is set on these threads.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/560c844c-f128-555b-40c6-31baff27537f@kernel.dk

parent aa81cb9d

arch/x86/include/asm/fpu/sched.h

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -39,7 +39,7 @@ extern void fpu_flush_thread(void);
	static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu)		static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu)
	{		{
	if (cpu_feature_enabled(X86_FEATURE_FPU) &&		if (cpu_feature_enabled(X86_FEATURE_FPU) &&
	!(current->flags & PF_KTHREAD)) {		!(current->flags & (PF_KTHREAD \| PF_IO_WORKER))) {
	save_fpregs_to_fpstate(old_fpu);		save_fpregs_to_fpstate(old_fpu);
	/*		/*
	* The save operation preserved register state, so the		* The save operation preserved register state, so the

arch/x86/kernel/fpu/context.h

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -57,7 +57,7 @@ static inline void fpregs_restore_userregs(void)
	struct fpu *fpu = &current->thread.fpu;		struct fpu *fpu = &current->thread.fpu;
	int cpu = smp_processor_id();		int cpu = smp_processor_id();

	if (WARN_ON_ONCE(current->flags & PF_KTHREAD))		if (WARN_ON_ONCE(current->flags & (PF_KTHREAD \| PF_IO_WORKER)))
	return;		return;

	if (!fpregs_state_valid(fpu, cpu)) {		if (!fpregs_state_valid(fpu, cpu)) {

arch/x86/kernel/fpu/core.c

+1 −1

Original line number	Original line	Diff line number	Diff line
	@@ -426,7 +426,7 @@ void kernel_fpu_begin_mask(unsigned int kfpu_mask)

	this_cpu_write(in_kernel_fpu, true);		this_cpu_write(in_kernel_fpu, true);

	if (!(current->flags & PF_KTHREAD) &&		if (!(current->flags & (PF_KTHREAD \| PF_IO_WORKER)) &&
	!test_thread_flag(TIF_NEED_FPU_LOAD)) {		!test_thread_flag(TIF_NEED_FPU_LOAD)) {
	set_thread_flag(TIF_NEED_FPU_LOAD);		set_thread_flag(TIF_NEED_FPU_LOAD);
	save_fpregs_to_fpstate(&current->thread.fpu);		save_fpregs_to_fpstate(&current->thread.fpu);