Module Name: src
Committed By: bouyer
Date: Sat Oct 22 22:42:21 UTC 2011
Modified Files:
src/sys/arch/xen/xen [cherry-xenmp]: clock.c
Log Message:
More improvements:
- Precise what tmutex protects
- springle some KASSERT(mutex_owned(&tmutex))
- the system time uses the CPU timecounter to get some precision;
don't mix local CPU timecounter with VCPU0's time, it won't work well.
Always use curcpu()'s time.
To generate a diff of this commit:
cvs rdiff -u -r1.54.6.6 -r1.54.6.7 src/sys/arch/xen/xen/clock.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/arch/xen/xen/clock.c
diff -u src/sys/arch/xen/xen/clock.c:1.54.6.6 src/sys/arch/xen/xen/clock.c:1.54.6.7
--- src/sys/arch/xen/xen/clock.c:1.54.6.6 Sat Oct 22 21:16:59 2011
+++ src/sys/arch/xen/xen/clock.c Sat Oct 22 22:42:20 2011
@@ -1,4 +1,4 @@
-/* $NetBSD: clock.c,v 1.54.6.6 2011/10/22 21:16:59 bouyer Exp $ */
+/* $NetBSD: clock.c,v 1.54.6.7 2011/10/22 22:42:20 bouyer Exp $ */
/*
*
@@ -29,7 +29,7 @@
#include "opt_xen.h"
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: clock.c,v 1.54.6.6 2011/10/22 21:16:59 bouyer Exp $");
+__KERNEL_RCSID(0, "$NetBSD: clock.c,v 1.54.6.7 2011/10/22 22:42:20 bouyer Exp $");
#include <sys/param.h>
#include <sys/cpu.h>
@@ -79,11 +79,12 @@ struct shadow {
struct timespec ts;
};
+/* Protects volatile variables ci_shadow & xen_clock_bias */
+static kmutex_t tmutex;
+
/* Per CPU shadow time values */
static volatile struct shadow ci_shadow[MAXCPUS];
-static kmutex_t tmutex; /* Protects volatile variables, below */
-
/* The time when the last hardclock(9) call should have taken place,
* per cpu.
*/
@@ -116,6 +117,7 @@ get_time_values_from_xen(struct cpu_info
volatile struct vcpu_time_info *t = &ci->ci_vcpu->time;
uint32_t tversion;
+ KASSERT(mutex_owned(&tmutex));
do {
shadow->time_version = t->version;
xen_rmb();
@@ -142,9 +144,11 @@ static inline int
time_values_up_to_date(struct cpu_info *ci)
{
int rv;
+ volatile struct shadow *shadow = &ci_shadow[ci->ci_cpuid];
+
KASSERT(ci != NULL);
+ KASSERT(mutex_owned(&tmutex));
- volatile struct shadow *shadow = &ci_shadow[ci->ci_cpuid];
xen_rmb();
rv = shadow->time_version == ci->ci_vcpu->time.version;
@@ -187,6 +191,7 @@ get_tsc_offset_ns(struct cpu_info *ci)
uint64_t tsc_delta, offset;
volatile struct shadow *shadow = &ci_shadow[ci->ci_cpuid];
+ KASSERT(mutex_owned(&tmutex));
tsc_delta = cpu_counter() - shadow->tsc_stamp;
offset = scale_delta(tsc_delta, shadow->freq_mul,
shadow->freq_shift);
@@ -212,53 +217,36 @@ get_vcpu_time(struct cpu_info *ci)
uint64_t offset, stime;
volatile struct shadow *shadow = &ci_shadow[ci->ci_cpuid];
- for (;;) {
+ KASSERT(mutex_owned(&tmutex));
+ do {
+ get_time_values_from_xen(ci);
offset = get_tsc_offset_ns(ci);
stime = shadow->system_time + offset;
/* if the timestamp went stale before we used it, refresh */
- if (time_values_up_to_date(ci)) {
- /*
- * Work around an intermittent Xen2 bug where, for
- * a period of 1<<32 ns, currently running domains
- * don't get their timer events as usual (and also
- * aren't preempted in favor of other runnable
- * domains). Setting the timer into the past in
- * this way causes it to fire immediately.
- */
- break;
- }
- get_time_values_from_xen(ci);
- }
+ } while (!time_values_up_to_date(ci));
return stime;
}
-/*
- * SMP note: system time always derives from Boot Processor.
- * Must be called at splhigh. See comment above on get_vcpu_time()
- */
-static uint64_t
-get_system_time(void)
-{
- return get_vcpu_time(&cpu_info_primary);
-
-}
-
static void
xen_wall_time(struct timespec *wt)
{
uint64_t nsec;
- struct cpu_info *ci = &cpu_info_primary;
+ struct cpu_info *ci = curcpu();
volatile struct shadow *shadow = &ci_shadow[ci->ci_cpuid];
mutex_enter(&tmutex);
- get_time_values_from_xen(ci);
- *wt = shadow->ts;
- nsec = wt->tv_nsec;
+ do {
+ /*
+ * Under Xen3, shadow->ts is the wall time less system time
+ * get_vcpu_time() will update shadow
+ */
+ nsec = get_vcpu_time(curcpu());
+ *wt = shadow->ts;
+ nsec += wt->tv_nsec;
- /* Under Xen3, this is the wall time less system time */
- nsec += get_system_time();
+ } while (!time_values_up_to_date(ci));
mutex_exit(&tmutex);
wt->tv_sec += nsec / 1000000000L;
wt->tv_nsec = nsec % 1000000000L;
@@ -300,7 +288,7 @@ xen_rtc_set(todr_chip_handle_t todr, str
op.u.settime.secs = tvp->tv_sec;
op.u.settime.nsecs = tvp->tv_usec * 1000;
mutex_enter(&tmutex);
- op.u.settime.system_time = get_system_time();
+ op.u.settime.system_time = get_vcpu_time(curcpu());
mutex_exit(&tmutex);
#if __XEN_INTERFACE_VERSION__ < 0x00030204
return HYPERVISOR_dom0_op(&op);
@@ -363,6 +351,7 @@ xen_delay(unsigned int n)
when = shadow->system_time + n * 1000;
while (shadow->system_time < when) {
mutex_exit(&tmutex);
+ HYPERVISOR_yield();
mutex_enter(&tmutex);
get_time_values_from_xen(ci);
}
@@ -459,10 +448,14 @@ xen_initclocks(void)
evtch = bind_virq_to_evtch(VIRQ_TIMER);
aprint_verbose("Xen clock: using event channel %d\n", evtch);
+ if (!tcdone) { /* Do this only once */
+ mutex_init(&tmutex, MUTEX_DEFAULT, IPL_CLOCK);
+ }
+ mutex_enter(&tmutex);
get_time_values_from_xen(ci);
vcpu_system_time[ci->ci_cpuid] = shadow->system_time;
+ mutex_exit(&tmutex);
if (!tcdone) { /* Do this only once */
- mutex_init(&tmutex, MUTEX_DEFAULT, IPL_CLOCK);
tc_init(&xen_timecounter);
}
/* The splhigh requirements start here. */
