[ovs-dev] [PATCH V2 3/5] timeval: Wake up all threads when time is warped.

Alex Wang alexw at nicira.com
Wed Oct 2 14:31:49 UTC 2013


This commit makes the main thread wake up all other threads when time is
warped.

Signed-off-by: Alex Wang <alexw at nicira.com>

---

v1 -> v2:
- change the code to make main thread wake up all other threads when time
  is warped.
- change the commit log.

---
 lib/poll-loop.c |    5 +++++
 lib/timeval.c   |   21 +++++++++++++++++++++
 lib/timeval.h   |    2 ++
 3 files changed, 28 insertions(+)

diff --git a/lib/poll-loop.c b/lib/poll-loop.c
index 4eb1187..97e4a2a 100644
--- a/lib/poll-loop.c
+++ b/lib/poll-loop.c
@@ -226,6 +226,11 @@ poll_block(void)
         COVERAGE_INC(poll_zero_timeout);
     }
 
+    /* For threads other than main thread, wait for timewarp. */
+    if (ovsthread_id_self()) {
+        timewarp_wait();
+    }
+
     retval = time_poll(loop->pollfds, loop->n_waiters,
                        loop->timeout_when, &elapsed);
     if (retval < 0) {
diff --git a/lib/timeval.c b/lib/timeval.c
index 223ed30..9c3646d 100644
--- a/lib/timeval.c
+++ b/lib/timeval.c
@@ -33,6 +33,7 @@
 #include "hmap.h"
 #include "ovs-thread.h"
 #include "signals.h"
+#include "seq.h"
 #include "unixctl.h"
 #include "util.h"
 #include "vlog.h"
@@ -57,6 +58,12 @@ static struct clock wall_clock;      /* CLOCK_REALTIME. */
 /* The monotonic time at which the time module was initialized. */
 static long long int boot_time;
 
+/* Reference to the seq struct.  Threads other than main thread can
+ * wait on timewarp_seq and be waken up when time is warped. */
+static struct seq *timewarp_seq;
+/* Last value of 'timewarp_seq' for each thread. */
+DEFINE_STATIC_PER_THREAD_DATA(uint64_t, last_seq, 0);
+
 /* Monotonic time in milliseconds at which to die with SIGALRM (if not
  * LLONG_MAX). */
 static long long int deadline = LLONG_MAX;
@@ -79,6 +86,7 @@ init_clock(struct clock *c, clockid_t id)
     ovs_mutex_init(&c->mutex);
     atomic_init(&c->slow_path, false);
     xclock_gettime(c->id, &c->cache);
+    timewarp_seq = seq_create();
 }
 
 static void
@@ -312,6 +320,17 @@ xclock_gettime(clock_t id, struct timespec *ts)
     }
 }
 
+/* Makes threads wait on timewarp_seq and
+ * be waken up when time is warped. */
+void
+timewarp_wait(void)
+{
+    uint64_t *last_seq = last_seq_get();
+
+    *last_seq = seq_read(timewarp_seq);
+    seq_wait(timewarp_seq, *last_seq);
+}
+
 static long long int
 timeval_diff_msec(const struct timeval *a, const struct timeval *b)
 {
@@ -509,6 +528,8 @@ timeval_warp_cb(struct unixctl_conn *conn,
     ovs_mutex_lock(&monotonic_clock.mutex);
     atomic_store(&monotonic_clock.slow_path, true);
     timespec_add(&monotonic_clock.warp, &monotonic_clock.warp, &ts);
+    /* Changes 'timewarp_seq' to wake up all waiting thread. */
+    seq_change(timewarp_seq);
     ovs_mutex_unlock(&monotonic_clock.mutex);
 
     unixctl_command_reply(conn, "warped");
diff --git a/lib/timeval.h b/lib/timeval.h
index 99b3af0..1bbfd5c 100644
--- a/lib/timeval.h
+++ b/lib/timeval.h
@@ -69,6 +69,8 @@ int get_cpu_usage(void);
 
 long long int time_boot_msec(void);
 
+void timewarp_wait(void);
+
 #ifdef  __cplusplus
 }
 #endif
-- 
1.7.9.5




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