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authorOleg Nesterov <oleg@redhat.com>2015-01-15 14:19:43 -0500
committerThomas Gleixner <tglx@linutronix.de>2015-01-20 07:53:07 -0500
commit14e153ef75eecae8fd0738ffb42120f4962a00cd (patch)
tree22fb7872fddb4c639d882ca602f4240c38acfaae /arch/x86/include/asm/i387.h
parent6ca7a8a15035add0a4f9b2fd658118d41dbeb20c (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.h2
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);
40 40
41static inline void kernel_fpu_begin(void) 41static inline void kernel_fpu_begin(void)
42{ 42{
43 WARN_ON_ONCE(!irq_fpu_usable());
44 preempt_disable(); 43 preempt_disable();
44 WARN_ON_ONCE(!irq_fpu_usable());
45 __kernel_fpu_begin(); 45 __kernel_fpu_begin();
46} 46}
47 47