Mailing List Archive

# HG changeset patch
# User Keir Fraser <keir.fraser@citrix.com>
# Date 1273573287 -3600
# Node ID 7d4deb86b9661b8585fc2b5c41334f2b34b0922b
# Parent 2077d6ad60780bbe0631c0dee1ef2e2b8eb03867
x86: Detect and handle unexpected platform-timer counter wrap.

Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
---
xen/arch/x86/time.c | 36 +++++++++++++++++++++++++++++-------
1 files changed, 29 insertions(+), 7 deletions(-)

diff -r 2077d6ad6078 -r 7d4deb86b966 xen/arch/x86/time.c
--- a/xen/arch/x86/time.c Tue May 11 11:19:23 2010 +0100
+++ b/xen/arch/x86/time.c Tue May 11 11:21:27 2010 +0100
@@ -571,24 +571,46 @@ static u64 plt_stamp; /* hard
static u64 plt_stamp; /* hardware-width platform counter stamp */
static struct timer plt_overflow_timer;

+static s_time_t __read_platform_stime(u64 platform_time)
+{
+ u64 diff = platform_time - platform_timer_stamp;
+ ASSERT(spin_is_locked(&platform_timer_lock));
+ return (stime_platform_stamp + scale_delta(diff, &plt_scale));
+}
+
static void plt_overflow(void *unused)
{
+ int i;
u64 count;
+ s_time_t now, plt_now, plt_wrap;

spin_lock_irq(&platform_timer_lock);
+
count = plt_src.read_counter();
plt_stamp64 += (count - plt_stamp) & plt_mask;
plt_stamp = count;
+
+ now = NOW();
+ plt_wrap = __read_platform_stime(plt_stamp64);
+ for ( i = 0; i < 10; i++ )
+ {
+ plt_now = plt_wrap;
+ plt_wrap = __read_platform_stime(plt_stamp64 + plt_mask + 1);
+ if ( ABS(plt_wrap - now) > ABS(plt_now - now) )
+ break;
+ plt_stamp64 += plt_mask + 1;
+ }
+ if ( i != 0 )
+ {
+ static bool_t warned_once;
+ if ( !test_and_set_bool(warned_once) )
+ printk("Platform timer appears to have unexpectedly wrapped "
+ "%u%s times.\n", i, (i == 10) ? " or more" : "");
+ }
+
spin_unlock_irq(&platform_timer_lock);

set_timer(&plt_overflow_timer, NOW() + plt_overflow_period);
-}
-
-static s_time_t __read_platform_stime(u64 platform_time)
-{
- u64 diff = platform_time - platform_timer_stamp;
- ASSERT(spin_is_locked(&platform_timer_lock));
- return (stime_platform_stamp + scale_delta(diff, &plt_scale));
}

static s_time_t read_platform_stime(void)

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