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: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Fenghua Yu <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Yu-cheng Yu <[email protected]> Signed-off-by: Ingo Molnar <[email protected]> --- 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; -- 2.11.0
