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	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)
		{
		if (cpu_feature_enabled(X86_FEATURE_FPU) &&
		!(current->flags & PF_KTHREAD)) {
		!(current->flags & (PF_KTHREAD \| PF_IO_WORKER))) {
		save_fpregs_to_fpstate(old_fpu);
		/*
		* The save operation preserved register state, so the

arch/x86/kernel/fpu/context.h

+1 −1

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

		if (!fpregs_state_valid(fpu, cpu)) {

arch/x86/kernel/fpu/core.c

+1 −1

Original line number	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);

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