Commit b6aa8555 authored by Ingo Molnar's avatar Ingo Molnar

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 <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Link: http://lkml.kernel.org/r/20170923130016.21448-18-mingo@kernel.orgSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent a10b6a16
......@@ -414,13 +414,20 @@ void fpu__drop(struct fpu *fpu)
{
preempt_disable();
if (fpu == &current->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;
......
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