diff options
author | Oleg Nesterov <oleg@redhat.com> | 2015-01-15 20:19:43 +0100 |
---|---|---|
committer | Thomas Gleixner <tglx@linutronix.de> | 2015-01-20 13:53:07 +0100 |
commit | 14e153ef75eecae8fd0738ffb42120f4962a00cd (patch) | |
tree | 22fb7872fddb4c639d882ca602f4240c38acfaae /arch/x86/include/asm/i387.h | |
parent | 6ca7a8a15035add0a4f9b2fd658118d41dbeb20c (diff) |
x86, fpu: Introduce per-cpu in_kernel_fpu state
interrupted_kernel_fpu_idle() tries to detect if kernel_fpu_begin()
is safe or not. In particular it should obviously deny the nested
kernel_fpu_begin() and this logic looks very confusing.
If use_eager_fpu() == T we rely on a) __thread_has_fpu() check in
interrupted_kernel_fpu_idle(), and b) on the fact that _begin() does
__thread_clear_has_fpu().
Otherwise we demand that the interrupted task has no FPU if it is in
kernel mode, this works because __kernel_fpu_begin() does clts() and
interrupted_kernel_fpu_idle() checks X86_CR0_TS.
Add the per-cpu "bool in_kernel_fpu" variable, and change this code
to check/set/clear it. This allows to do more cleanups and fixes, see
the next changes.
The patch also moves WARN_ON_ONCE() under preempt_disable() just to
make this_cpu_read() look better, this is not really needed. And in
fact I think we should move it into __kernel_fpu_begin().
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/20150115191943.GB27332@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 | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h index ed8089d69094..5e275d31802e 100644 --- a/arch/x86/include/asm/i387.h +++ b/arch/x86/include/asm/i387.h @@ -40,8 +40,8 @@ extern void __kernel_fpu_end(void); static inline void kernel_fpu_begin(void) { - WARN_ON_ONCE(!irq_fpu_usable()); preempt_disable(); + WARN_ON_ONCE(!irq_fpu_usable()); __kernel_fpu_begin(); } |