Fix preemption and SMP problems in the FP emulator code.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 17 insertions, 2 deletions

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 15fed0202154..b3ecd02757cb 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -551,6 +551,14 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)
 
                 preempt_disable();
 
+#ifdef CONFIG_PREEMPT
+                if (!is_fpu_owner()) {
+                        /* We might lose fpu before disabling preempt... */
+                        own_fpu();
+                        BUG_ON(!used_math());
+                        restore_fp(current);
+                }
+#endif
                 /*
                  * Unimplemented operation exception.  If we've got the full
                  * software emulator on-board, let's use it...
@@ -562,11 +570,18 @@ asmlinkage void do_fpe(struct pt_regs *regs, unsigned long fcr31)
                  * a bit extreme for what should be an infrequent event.
                  */
                 save_fp(current);
+                /* Ensure 'resume' not overwrite saved fp context again. */
+                lose_fpu();
+
+                preempt_enable();
 
                 /* Run the emulator */
                 sig = fpu_emulator_cop1Handler (0, regs,
                         &current->thread.fpu.soft);
 
+                preempt_disable();
+
+                own_fpu();      /* Using the FPU again.  */
                 /*
                  * We can't allow the emulated instruction to leave any of
                  * the cause bit set in $fcr31.
@@ -712,6 +727,8 @@ asmlinkage void do_cpu(struct pt_regs *regs)
                         set_used_math();
                 }
 
+                preempt_enable();
+
                 if (!cpu_has_fpu) {
                         int sig = fpu_emulator_cop1Handler(0, regs,
                                                 &current->thread.fpu.soft);
@@ -719,8 +736,6 @@ asmlinkage void do_cpu(struct pt_regs *regs)
                                 force_sig(sig, current);
                 }
 
-                preempt_enable();
-
                 return;
 
         case 2: