diff options
| author | Oleg Nesterov <oleg@redhat.com> | 2015-01-15 20:20:28 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2015-01-20 13:53:07 +0100 |
| commit | 7575637ab293861a799f3bbafe0d8c597389f4e9 (patch) | |
| tree | 52cc8c7a21eecaa53bbe3222864bcd3d8e482851 /arch/x86/kernel/i387.c | |
| parent | 33a3ebdc077fd85f1bf4d4586eea579b297461ae (diff) | |
x86, fpu: Fix math_state_restore() race with kernel_fpu_begin()
math_state_restore() can race with kernel_fpu_begin() if irq comes
right after __thread_fpu_begin(), __save_init_fpu() will overwrite
fpu->state we are going to restore.
Add 2 simple helpers, kernel_fpu_disable() and kernel_fpu_enable()
which simply set/clear in_kernel_fpu, and change math_state_restore()
to exclude kernel_fpu_begin() in between.
Alternatively we could use local_irq_save/restore, but probably these
new helpers can have more users.
Perhaps they should disable/enable preemption themselves, in this case
we can remove preempt_disable() in __restore_xstate_sig().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: matt.fleming@intel.com
Cc: bp@suse.de
Cc: pbonzini@redhat.com
Cc: luto@amacapital.net
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Suresh Siddha <sbsiddha@gmail.com>
Link: http://lkml.kernel.org/r/20150115192028.GD27332@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/kernel/i387.c')
| -rw-r--r-- | arch/x86/kernel/i387.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index 12088a3f459f..81049ffab2d6 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -21,6 +21,17 @@ static DEFINE_PER_CPU(bool, in_kernel_fpu); +void kernel_fpu_disable(void) +{ + WARN_ON(this_cpu_read(in_kernel_fpu)); + this_cpu_write(in_kernel_fpu, true); +} + +void kernel_fpu_enable(void) +{ + this_cpu_write(in_kernel_fpu, false); +} + /* * Were we in an interrupt that interrupted kernel mode? * |