Re: [PATCH 1/3] do_fpe() cleanup

[Atsushi Nemoto <anemo@xxxxxxxxxxxxx>]

On Sat, 25 Nov 2006 00:03:44 +0900 (JST), Atsushi Nemoto <anemo@xxxxxxxxxxxxx> wrote:
> If we had already lost FPU before disabling preempt, we do not have to
> own it at all.  And we do not prevent preemption when managing saved
> FCR31 if we did not have FPU ownership.
> 
> Signed-off-by: Atsushi Nemoto <anemo@xxxxxxxxxxxxx>
> ---
>  traps.c |   22 ++++++++--------------
>  1 files changed, 8 insertions(+), 14 deletions(-)

Ping.  This patch is dependent from other fp_context patches and
should be safe and harmless.  Are there any problems?


diff --git a/arch/mips/kernel/traps.c b/arch/mips/kernel/traps.c
index 9fda1b8..b18aeb6 100644
--- a/arch/mips/kernel/traps.c
+++ b/arch/mips/kernel/traps.c
@@ -614,16 +614,6 @@ asmlinkage void do_fpe(struct pt_regs *r
 	if (fcr31 & FPU_CSR_UNI_X) {
 		int sig;
 
-		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...
@@ -634,7 +624,11 @@ #endif
 		 * register operands before invoking the emulator, which seems
 		 * a bit extreme for what should be an infrequent event.
 		 */
-		save_fp(current);
+		preempt_disable();
+
+		/* We might have lost fpu before disabling preempt... */
+		if (is_fpu_owner())
+			save_fp(current);
 		/* Ensure 'resume' not overwrite saved fp context again. */
 		lose_fpu();
 
@@ -643,15 +637,15 @@ #endif
 		/* Run the emulator */
 		sig = fpu_emulator_cop1Handler (regs, &current->thread.fpu, 1);
 
-		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.
 		 */
 		current->thread.fpu.fcr31 &= ~FPU_CSR_ALL_X;
 
+		preempt_disable();
+
+		own_fpu();	/* Using the FPU again.  */
 		/* Restore the hardware register state */
 		restore_fp(current);