commit cd21dfcfbb5c43de54f6be795dde07397da2bc2f
author Ralf Baechle <ralf@linux-mips.org> Thu Apr 28 13:39:10 2005 +0000
committer Ralf Baechle <ralf@linux-mips.org> Sat Oct 29 19:31:12 2005 +0100
tree ed3a6c46fd6aabac95c99b1e816493fcb5f788f8
parent 63b2d2f4d2073ac3452ce977d27cc81eabaa61a3

Fix preemption and SMP problems in the FP emulator code.

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

arch/mips/kernel/traps.c

diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 15fed02..b3ecd02 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -551,6 +551,14 @@
 
 		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 @@
 		 * 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 @@
 			set_used_math();
 		}
 
+		preempt_enable();
+
 		if (!cpu_has_fpu) {
 			int sig = fpu_emulator_cop1Handler(0, regs,
 						&current->thread.fpu.soft);
@@ -719,8 +736,6 @@
 				force_sig(sig, current);
 		}
 
-		preempt_enable();
-
 		return;
 
 	case 2: