arm: fix a preempt_count() corruption for CONFIG_PREEMPT=n

Hi All,

After a hard days' work, I've managed to track down a ghost causing sporadic kernel warnings and system crashes. The patch applies for the HEAD of linux-stable. I don't know how to create and submit patches correctly, and hope that somebody will pick it up...

Regards,
Patrik

From: Patrik Kluba <[email protected]>
Date: Fri, 14 Dec 2012 14:36:27 +0100
Subject: [PATCH] arm: fix a preempt_count() corruption for CONFIG_PREEMPT=n

All the preempt-disabling assembly code is under CONFIG_PREEMPT, while VFP_bounce calls preempt_enable() uncoditionally, leading to a preempt_count() corruption (gets set to 0xffffffff). Fix the imbalance by adding #ifdef CONFIG_PREEMPT before preempt_enable().

---
 arch/arm/vfp/vfpmodule.c |    3 +++
 1 file changed, 3 insertions(+)

index 3b44e0d..2184f7e 100644
@@ -428,7 +428,10 @@ void VFP_bounce(u32 trigger, u32 fpexc, struct pt_regs *regs)
 	if (exceptions)
 		vfp_raise_exceptions(exceptions, trigger, orig_fpscr, regs);
  exit:
+#ifdef CONFIG_PREEMPT
 	preempt_enable();
+#endif
+	return;
 }
 
 static void vfp_enable(void *unused)

1.7.10.4