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

diff --git a/arch/x86/include/asm/fpu/sched.h b/arch/x86/include/asm/fpu/sched.h
index b2486b2..c2d6cd7 100644 (file)
--- a/arch/x86/include/asm/fpu/sched.h
+++ b/arch/x86/include/asm/fpu/sched.h
@@ -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

diff --git a/arch/x86/kernel/fpu/context.h b/arch/x86/kernel/fpu/context.h
index 958accf..9fcfa5c 100644 (file)
--- a/arch/x86/kernel/fpu/context.h
+++ b/arch/x86/kernel/fpu/context.h
@@ -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)) {

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 9baa89a..2babc53 100644 (file)
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -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);