From b6aa85558d7e7b18fc3470d2bc1731d2205dd275 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Sat, 23 Sep 2017 15:00:00 +0200 Subject: [PATCH] x86/fpu: Split the state handling in fpu__drop() Prepare fpu__drop() to use fpu->fpregs_active. There are two distinct usecases for fpu__drop() in this context: exit_thread() when called for 'current' in exit(), and when called for another task in fork(). This patch does not change behavior, it only adds a couple of debug checks and structures the code to make the ->fpregs_active change more obviously correct. All the complications will be removed later on. Cc: Andrew Morton Cc: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: Eric Biggers Cc: Fenghua Yu Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Peter Zijlstra Cc: Rik van Riel Cc: Thomas Gleixner Cc: Yu-cheng Yu Link: http://lkml.kernel.org/r/20170923130016.21448-18-mingo@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/kernel/fpu/core.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index b7dc3833d41a..815dfba7781a 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -414,12 +414,19 @@ void fpu__drop(struct fpu *fpu) { preempt_disable(); - if (fpu->fpregs_active) { - /* Ignore delayed exceptions from user space */ - asm volatile("1: fwait\n" - "2:\n" - _ASM_EXTABLE(1b, 2b)); - fpregs_deactivate(fpu); + if (fpu == ¤t->thread.fpu) { + WARN_ON_FPU(fpu->fpstate_active != fpu->fpregs_active); + + if (fpu->fpregs_active) { + /* Ignore delayed exceptions from user space */ + asm volatile("1: fwait\n" + "2:\n" + _ASM_EXTABLE(1b, 2b)); + if (fpu->fpregs_active) + fpregs_deactivate(fpu); + } + } else { + WARN_ON_FPU(fpu->fpregs_active); } fpu->fpstate_active = 0; -- 2.39.5