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/include/asm/i387.h | |
| 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/include/asm/i387.h')
| -rw-r--r-- | arch/x86/include/asm/i387.h | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h index 5e275d31802e..6eb6fcb83f63 100644 --- a/arch/x86/include/asm/i387.h +++ b/arch/x86/include/asm/i387.h @@ -51,6 +51,10 @@ static inline void kernel_fpu_end(void) preempt_enable(); } +/* Must be called with preempt disabled */ +extern void kernel_fpu_disable(void); +extern void kernel_fpu_enable(void); + /* * Some instructions like VIA's padlock instructions generate a spurious * DNA fault but don't modify SSE registers. And these instructions |