bitkeeper revision 1.1159.1.213 (416517f3vAbY9ISDviAe0Gjenl6dKw)

Take better care of over time consistency in XenLinux.
Avoid spinning on serial line with interrupts disabled in Xen.

linux-2.4.27-xen-sparse/arch/xen/kernel/time.c

@@ -224,7 +224,7 @@ static void __get_time_values_from_xen(void)
 }
 
 #define TIME_VALUES_UP_TO_DATE \
-    (shadow_time_version == HYPERVISOR_shared_info->time_version2)
+ ({ rmb(); (shadow_time_version == HYPERVISOR_shared_info->time_version2); })
 
 
 /*
@@ -393,11 +393,14 @@ static inline void do_timer_interrupt(int irq, void *dev_id,
     unsigned long ticks = 0;
     long sec_diff;
 
+ retry:
     __get_time_values_from_xen();
 
     if ( (delta = (s64)(shadow_system_time + __get_time_delta_usecs() * 1000 -
 						processed_system_time)) < 0 )
     {
+		if (!TIME_VALUES_UP_TO_DATE)
+			goto retry;
         printk("Timer ISR: Time went backwards: %lld\n", delta);
         return;
     }

linux-2.6.8.1-xen-sparse/arch/xen/i386/kernel/time.c

@@ -172,7 +172,7 @@ static void __get_time_values_from_xen(void)
 }
 
 #define TIME_VALUES_UP_TO_DATE \
-	(shadow_time_version == HYPERVISOR_shared_info->time_version2)
+ ({ rmb(); (shadow_time_version == HYPERVISOR_shared_info->time_version2); })
 
 /*
  * This version of gettimeofday has microsecond resolution
@@ -367,12 +367,15 @@ static inline void do_timer_interrupt(int irq, void *dev_id,
 	s64 delta, nsec;
 	long sec_diff, wtm_nsec;
 
+ retry:
 	__get_time_values_from_xen();
 
 	delta = (s64)(shadow_system_time +
 		      (cur_timer->get_offset() * NSEC_PER_USEC) -
 		      processed_system_time);
 	if (delta < 0) {
+		if (!TIME_VALUES_UP_TO_DATE)
+			goto retry;
 		printk("Timer ISR: Time went backwards: %lld\n", delta);
 		return;
 	}

xen/drivers/char/serial.c

@@ -132,6 +132,9 @@ static void serial_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 
 static inline void __serial_putc(uart_t *uart, int handle, unsigned char c)
 {
+    unsigned long flags;
+    int space;
+
     if ( (c == '\n') && (handle & SERHND_COOKED) )
         __serial_putc(uart, handle, '\r');
 
@@ -140,10 +143,13 @@ static inline void __serial_putc(uart_t *uart, int handle, unsigned char c)
     else if ( handle & SERHND_LO )
         c &= 0x7f;
 
-    while ( !(inb(uart->io_base + LSR) & LSR_THRE) )
-        barrier();
-
-    outb(c, uart->io_base + THR);
+    do { 
+        spin_lock_irqsave(&uart->lock, flags);
+        if ( (space = (inb(uart->io_base + LSR) & LSR_THRE)) )
+            outb(c, uart->io_base + THR);
+        spin_unlock_irqrestore(&uart->lock, flags);
+    }
+    while ( !space );
 }
 
 #define PARSE_ERR(_f, _a...)                 \
@@ -376,32 +382,22 @@ void serial_set_rx_handler(int handle, serial_rx_fn fn)
 void serial_putc(int handle, unsigned char c)
 {
     uart_t *uart = &com[handle & SERHND_IDX];
-    unsigned long flags;
 
     if ( handle == -1 )
         return;
 
-    spin_lock_irqsave(&uart->lock, flags);
-
     __serial_putc(uart, handle, c);
-
-    spin_unlock_irqrestore(&uart->lock, flags);
 }
 
 void serial_puts(int handle, const unsigned char *s)
 {
     uart_t *uart = &com[handle & SERHND_IDX];
-    unsigned long flags;
 
     if ( handle == -1 )
         return;
 
-    spin_lock_irqsave(&uart->lock, flags);
-
     while ( *s != '\0' )
         __serial_putc(uart, handle, *s++);
-
-    spin_unlock_irqrestore(&uart->lock, flags);
 }
 
 /* Returns TRUE if given character (*pc) matches the serial handle. */