[MIPS] Retry {save,restore}_fp_context if failed in atomic context.

The save_fp_context()/restore_fp_context() might sleep on accessing
user stack and therefore might lose FPU ownership in middle of them.

If these function failed due to "in_atomic" test in do_page_fault,
touch the sigcontext area in non-atomic context and retry these
save/restore operation.

This is a replacement of a (broken) fix which was titled "Allow CpU
exception in kernel partially".

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 7 insertions, 2 deletions

diff --git a/include/asm-mips/fpu.h b/include/asm-mips/fpu.h
index 71436f90203f..b414a7d9db43 100644
--- a/include/asm-mips/fpu.h
+++ b/include/asm-mips/fpu.h
@@ -100,14 +100,19 @@ static inline void __own_fpu(void)
         set_thread_flag(TIF_USEDFPU);
 }
 
-static inline void own_fpu(int restore)
+static inline void own_fpu_inatomic(int restore)
 {
-        preempt_disable();
         if (cpu_has_fpu && !__is_fpu_owner()) {
                 __own_fpu();
                 if (restore)
                         _restore_fp(current);
         }
+}
+
+static inline void own_fpu(int restore)
+{
+        preempt_disable();
+        own_fpu_inatomic(restore);
         preempt_enable();
 }