x86-kprobes-Fix-missed-preemptions.patch

From fdf53c05e5e9f7a48bd637fde223565ae472f5fa Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Fri, 3 Jul 2009 08:29:25 -0500
Subject: [PATCH] x86: kprobes: Fix missed preemptions

commit fc1193fdc2f917421949f07022bc92392ce86a7e in tip.

preempt_enable_no_resched() is only correct when we call schedule
right away. The use in kprobes is just increasing latencies for no
reason.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c
index b43bbae..d973852 100644
--- a/arch/x86/kernel/kprobes.c
+++ b/arch/x86/kernel/kprobes.c
@@ -468,7 +468,7 @@ static void __kprobes setup_singlestep(struct kprobe *p, struct pt_regs *regs,
 		 * stepping.
 		 */
 		regs->ip = (unsigned long)p->ainsn.insn;
-		preempt_enable_no_resched();
+		preempt_enable();
 		return;
 	}
 #endif
@@ -587,7 +587,7 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
 		}
 	} /* else: not a kprobe fault; let the kernel handle it */
 
-	preempt_enable_no_resched();
+	preempt_enable();
 	return 0;
 }
 
@@ -893,7 +893,7 @@ static int __kprobes post_kprobe_handler(struct pt_regs *regs)
 	}
 	reset_current_kprobe();
 out:
-	preempt_enable_no_resched();
+	preempt_enable();
 
 	/*
 	 * if somebody else is singlestepping across a probe point, flags
@@ -927,7 +927,7 @@ int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr)
 			restore_previous_kprobe(kcb);
 		else
 			reset_current_kprobe();
-		preempt_enable_no_resched();
+		preempt_enable();
 		break;
 	case KPROBE_HIT_ACTIVE:
 	case KPROBE_HIT_SSDONE:
@@ -1074,7 +1074,7 @@ int __kprobes longjmp_break_handler(struct kprobe *p, struct pt_regs *regs)
 		memcpy((kprobe_opcode_t *)(kcb->jprobe_saved_sp),
 		       kcb->jprobes_stack,
 		       MIN_STACK_SIZE(kcb->jprobe_saved_sp));
-		preempt_enable_no_resched();
+		preempt_enable();
 		return 1;
 	}
 	return 0;
-- 
1.7.1.1