pmap: Fix busy loop waiting for pmap users

We need to avoid the kernel optimizing away the read from
pmap->cpus_using. Use a standard relaxing instruction for that.

5 files changed, 12 insertions, 12 deletions

diff --git a/i386/i386/lock.h b/i386/i386/lock.h
index 1450fe03..4b445ae4 100644
--- a/i386/i386/lock.h
+++ b/i386/i386/lock.h
@@ -62,7 +62,7 @@
     ({ \
 	while(_simple_lock_xchg_(l, 1)) \
 	    while (*(volatile int *)&(l)->lock_data) \
-		__asm ("pause"); \
+		cpu_pause(); \
 	0; \
     })
 
diff --git a/i386/i386/mp_desc.c b/i386/i386/mp_desc.c
index e6fcbf62..4b5a78ea 100644
--- a/i386/i386/mp_desc.c
+++ b/i386/i386/mp_desc.c
@@ -269,7 +269,7 @@ cpu_ap_main()
     int cpu = apic_get_cpu_kernel_id(apic_id);
 
     do {
-        asm volatile ("pause" : : : "memory");
+	cpu_pause();
     } while (bspdone != cpu);
 
     __sync_synchronize();
@@ -319,7 +319,7 @@ start_other_cpus(void)
 
 		bspdone++;
 		do {
-			asm volatile ("pause" : : : "memory");
+			cpu_pause();
 		} while (machine_slot[cpu].running == FALSE);
 
 		__sync_synchronize();
diff --git a/i386/i386/smp.c b/i386/i386/smp.c
index 7441ffbb..c0149a3b 100644
--- a/i386/i386/smp.c
+++ b/i386/i386/smp.c
@@ -29,8 +29,6 @@
 
 #include <kern/smp.h>
 
-#define pause_memory	asm volatile ("pause" : : : "memory")
-
 /*
  * smp_data_init: initialize smp_data structure
  * Must be called after smp_init(), once all APIC structures
@@ -56,13 +54,13 @@ void smp_pmap_update(unsigned apic_id)
     apic_send_ipi(NO_SHORTHAND, FIXED, PHYSICAL, ASSERT, EDGE, CALL_SINGLE_FUNCTION_BASE, apic_id);
 
     do {
-        pause_memory;
+        cpu_pause();
     } while(lapic->icr_low.delivery_status == SEND_PENDING);
 
     apic_send_ipi(NO_SHORTHAND, FIXED, PHYSICAL, DE_ASSERT, EDGE, CALL_SINGLE_FUNCTION_BASE, apic_id);
 
     do {
-        pause_memory;
+        cpu_pause();
     } while(lapic->icr_low.delivery_status == SEND_PENDING);
 
     cpu_intr_restore(flags);
@@ -81,7 +79,7 @@ void smp_startup_cpu(unsigned apic_id, unsigned vector)
 
     /* Wait for delivery */
     do {
-        pause_memory;
+        cpu_pause();
     } while(lapic->icr_low.delivery_status == SEND_PENDING);
 
     /* Deassert INIT IPI */
@@ -89,7 +87,7 @@ void smp_startup_cpu(unsigned apic_id, unsigned vector)
 
     /* Wait for delivery */
     do {
-        pause_memory;
+        cpu_pause();
     } while(lapic->icr_low.delivery_status == SEND_PENDING);
 
     /* Wait 10 msec */
@@ -106,7 +104,7 @@ void smp_startup_cpu(unsigned apic_id, unsigned vector)
 
     /* Wait for delivery */
     do {
-        pause_memory;
+        cpu_pause();
     } while(lapic->icr_low.delivery_status == SEND_PENDING);
 
     /* Second StartUp IPI */
@@ -117,7 +115,7 @@ void smp_startup_cpu(unsigned apic_id, unsigned vector)
 
     /* Wait for delivery */
     do {
-        pause_memory;
+        cpu_pause();
     } while(lapic->icr_low.delivery_status == SEND_PENDING);
 
     printf("done\n");
diff --git a/i386/i386/smp.h b/i386/i386/smp.h
index 79337022..1faa39cd 100644
--- a/i386/i386/smp.h
+++ b/i386/i386/smp.h
@@ -25,4 +25,6 @@ int smp_init(void);
 void smp_pmap_update(unsigned apic_id);
 void smp_startup_cpu(unsigned apic_id, unsigned vector);
 
+#define cpu_pause() asm volatile ("pause" : : : "memory")
+
 #endif
diff --git a/i386/intel/pmap.c b/i386/intel/pmap.c
index 129e600b..0387fa8d 100644
--- a/i386/intel/pmap.c
+++ b/i386/intel/pmap.c
@@ -300,7 +300,7 @@ lock_data_t	pmap_system_lock;
 	    /* using the pmap */ \
 	    signal_cpus(users, (pmap), (s), (e)); \
 	    while ((pmap)->cpus_using & cpus_active & ~cpu_mask) \
-		continue; \
+		cpu_pause(); \
 	} \
  \
 	/* invalidate our own TLB if pmap is in use */ \