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| 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/kernel/i387.c | |
| parent | 6ca7a8a15035add0a4f9b2fd658118d41dbeb20c (diff) | |
| download | linux-14e153ef75eecae8fd0738ffb42120f4962a00cd.tar.bz2 | |
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/kernel/i387.c')
| -rw-r--r-- | arch/x86/kernel/i387.c | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/kernel/i387.c b/arch/x86/kernel/i387.c index a9a4229f6161..a81572338243 100644 --- a/arch/x86/kernel/i387.c +++ b/arch/x86/kernel/i387.c @@ -19,6 +19,8 @@ #include <asm/fpu-internal.h> #include <asm/user.h> +static DEFINE_PER_CPU(bool, in_kernel_fpu); + /* * Were we in an interrupt that interrupted kernel mode? * @@ -33,6 +35,9 @@ */ static inline bool interrupted_kernel_fpu_idle(void) { + if (this_cpu_read(in_kernel_fpu)) + return false; + if (use_eager_fpu()) return __thread_has_fpu(current); @@ -73,6 +78,8 @@ void __kernel_fpu_begin(void) { struct task_struct *me = current; + this_cpu_write(in_kernel_fpu, true); + if (__thread_has_fpu(me)) { __thread_clear_has_fpu(me); __save_init_fpu(me); @@ -99,6 +106,8 @@ void __kernel_fpu_end(void) } else { stts(); } + + this_cpu_write(in_kernel_fpu, false); } EXPORT_SYMBOL(__kernel_fpu_end); |