From b68e846fa236b7b7beeb23a84108fb713272440d Mon Sep 17 00:00:00 2001
From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Fri, 27 Aug 2010 19:39:42 -0700
Subject: [PATCH] kernel - Adjust contention handler

* Simplify handle_cpu_contention_mask() a little.  For vkernels we
  call pthread_yield().

* Just call cpu_pause() in cpu_spinlock_contested().  Don't do anything
  fancier, the routine is called as part of the exponential backoff
  code.
---
 sys/platform/pc32/i386/machdep.c         |  4 +---
 sys/platform/pc64/x86_64/machdep.c       |  7 ++++++-
 sys/platform/vkernel/i386/cpu_regs.c     | 12 +++---------
 sys/platform/vkernel64/x86_64/cpu_regs.c | 11 ++++-------
 4 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/sys/platform/pc32/i386/machdep.c b/sys/platform/pc32/i386/machdep.c
index 3a0c741d30..1ccf9b0779 100644
--- a/sys/platform/pc32/i386/machdep.c
+++ b/sys/platform/pc32/i386/machdep.c
@@ -954,10 +954,8 @@ handle_cpu_contention_mask(void)
 
 	mask = cpu_contention_mask;
 	cpu_ccfence();
-	if (mask && bsfl(mask) != mycpu->gd_cpuid) {
-		cpu_pause();
+	if (mask && bsfl(mask) != mycpu->gd_cpuid)
 		DELAY(2);
-	}
 }
 
 /*
diff --git a/sys/platform/pc64/x86_64/machdep.c b/sys/platform/pc64/x86_64/machdep.c
index 22438fb18e..426462d336 100644
--- a/sys/platform/pc64/x86_64/machdep.c
+++ b/sys/platform/pc64/x86_64/machdep.c
@@ -975,7 +975,12 @@ cpu_idle(void)
 void
 handle_cpu_contention_mask(void)
 {
-	cpu_pause();
+        cpumask_t mask;
+
+        mask = cpu_contention_mask;
+        cpu_ccfence();
+        if (mask && bsfl(mask) != mycpu->gd_cpuid)
+                DELAY(2);
 }
 
 /*
diff --git a/sys/platform/vkernel/i386/cpu_regs.c b/sys/platform/vkernel/i386/cpu_regs.c
index dc98099fe4..442a3d8d36 100644
--- a/sys/platform/vkernel/i386/cpu_regs.c
+++ b/sys/platform/vkernel/i386/cpu_regs.c
@@ -109,6 +109,7 @@
 #include <sys/ptrace.h>
 #include <machine/sigframe.h>
 #include <unistd.h>		/* umtx_* functions */
+#include <pthread.h>		/* pthread_yield */
 
 extern void dblfault_handler (void);
 
@@ -784,11 +785,8 @@ handle_cpu_contention_mask(void)
 
 	mask = cpu_contention_mask;
 	cpu_ccfence();
-	if (mask && bsfl(mask) != mycpu->gd_cpuid) {
-		cpu_pause();
-		usleep(1000);
-	}
-	/* usleep(1000); */
+	if (mask && bsfl(mask) != mycpu->gd_cpuid)
+		pthread_yield();
 }
 
 /*
@@ -802,10 +800,6 @@ void
 cpu_spinlock_contested(void)
 {
 	cpu_pause();
-	/*
-	crit_enter();
-	usleep(1000);
-	crit_exit();*/
 }
 
 #endif
diff --git a/sys/platform/vkernel64/x86_64/cpu_regs.c b/sys/platform/vkernel64/x86_64/cpu_regs.c
index 03e347bab6..fe6a46b562 100644
--- a/sys/platform/vkernel64/x86_64/cpu_regs.c
+++ b/sys/platform/vkernel64/x86_64/cpu_regs.c
@@ -106,6 +106,7 @@
 #include <sys/ptrace.h>
 #include <machine/sigframe.h>
 #include <unistd.h>		/* umtx_* functions */
+#include <pthread.h>		/* pthread_yield() */
 
 extern void dblfault_handler (void);
 
@@ -778,10 +779,8 @@ handle_cpu_contention_mask(void)
 
 	mask = cpu_contention_mask;
 	cpu_ccfence();
-	if (mask && bsfl(mask) != mycpu->gd_cpuid) {
-		cpu_pause();
-		usleep(1000);
-	}
+	if (mask && bsfl(mask) != mycpu->gd_cpuid)
+		pthread_yield();
 }
 
 /*
@@ -794,9 +793,7 @@ handle_cpu_contention_mask(void)
 void
 cpu_spinlock_contested(void)
 {
-	crit_enter();
-	usleep(1000);
-	crit_exit();
+	cpu_pause();
 }
 
 #endif
-- 
2.41.0