Mailing List Archive

# HG changeset patch
# User Keir Fraser <keir.fraser@citrix.com>
# Date 1271093313 -3600
# Node ID 9471200daee46c5a6f3b054b0a53f95545386029
# Parent 94cae4dfa25bcf9aaeb93fb374926cb40411ebdf
xentrace: fix lost records resume

Reorder the SCHED_SWITCH trace before the runstate change trace to fix
a problem with the lost records "resume" code.

Namely: The "lost records" trace includes the currently running
process. But during SCHED_SWITCH, it reads the wrong value, confusing
xenalyze. Making sure there are no trace records between runstate
change trace and the actual context switch fixes it.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>
---
xen/common/schedule.c | 14 ++++++++++----
1 files changed, 10 insertions(+), 4 deletions(-)

diff -r 94cae4dfa25b -r 9471200daee4 xen/common/schedule.c
--- a/xen/common/schedule.c Mon Apr 12 17:54:48 2010 +0100
+++ b/xen/common/schedule.c Mon Apr 12 18:28:33 2010 +0100
@@ -877,6 +877,11 @@ static void schedule(void)
next_slice.time);

ASSERT(prev->runstate.state == RUNSTATE_running);
+
+ TRACE_4D(TRC_SCHED_SWITCH,
+ prev->domain->domain_id, prev->vcpu_id,
+ next->domain->domain_id, next->vcpu_id);
+
vcpu_runstate_change(
prev,
(test_bit(_VPF_blocked, &prev->pause_flags) ? RUNSTATE_blocked :
@@ -887,6 +892,11 @@ static void schedule(void)
ASSERT(next->runstate.state != RUNSTATE_running);
vcpu_runstate_change(next, RUNSTATE_running, now);

+ /*
+ * NB. Don't add any trace records from here until the actual context
+ * switch, else lost_records resume will not work properly.
+ */
+
ASSERT(!next->is_running);
next->is_running = 1;

@@ -899,10 +909,6 @@ static void schedule(void)
/* Ensure that the domain has an up-to-date time base. */
update_vcpu_system_time(next);
vcpu_periodic_timer_work(next);
-
- TRACE_4D(TRC_SCHED_SWITCH,
- prev->domain->domain_id, prev->vcpu_id,
- next->domain->domain_id, next->vcpu_id);

context_switch(prev, next);
}

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