It could be possible that the thread misses a signal when it reads the
change_seq again after reload. Also, the counter has no dependent
data, so the memory model for the atomic read can be relaxed.
Signed-off-by: Jarno Rajahalme <jrajaha...@nicira.com>
---
lib/dpif-netdev.c | 27 ++++++++++++++-------------
1 file changed, 14 insertions(+), 13 deletions(-)
diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
index a458f24..7401293 100644
--- a/lib/dpif-netdev.c
+++ b/lib/dpif-netdev.c
@@ -297,6 +297,8 @@ struct pmd_thread {
atomic_uint change_seq;
};
+#define PMD_INITIAL_SEQ 1
+
/* Interface to netdev-based datapath. */
struct dpif_netdev {
struct dpif dpif;
@@ -613,10 +615,10 @@ dp_netdev_reload_pmd_threads(struct dp_netdev *dp)
for (i = 0; i < dp->n_pmd_threads; i++) {
struct pmd_thread *f = &dp->pmd_threads[i];
- int id;
+ int old_seq;
- atomic_add(&f->change_seq, 1, &id);
- }
+ atomic_add_explicit(&f->change_seq, 1, &old_seq, memory_order_relaxed);
+ }
}
static uint32_t
@@ -1701,7 +1703,7 @@ pmd_thread_main(void *f_)
struct dp_netdev *dp = f->dp;
unsigned int lc = 0;
struct rxq_poll *poll_list;
- unsigned int port_seq;
+ unsigned int port_seq = PMD_INITIAL_SEQ;
int poll_cnt;
int i;
@@ -1711,10 +1713,8 @@ pmd_thread_main(void *f_)
pmd_thread_setaffinity_cpu(f->id);
reload:
poll_cnt = pmd_load_queues(f, &poll_list, poll_cnt);
- atomic_read(&f->change_seq, &port_seq);
for (;;) {
- unsigned int c_port_seq;
int i;
for (i = 0; i < poll_cnt; i++) {
@@ -1722,14 +1722,15 @@ reload:
}
if (lc++ > 1024) {
- ovsrcu_quiesce();
+ unsigned int seq;
- /* XXX: need completely userspace based signaling method.
- * to keep this thread entirely in userspace.
- * For now using atomic counter. */
lc = 0;
- atomic_read_explicit(&f->change_seq, &c_port_seq,
memory_order_consume);
- if (c_port_seq != port_seq) {
+
+ ovsrcu_quiesce();
+
+ atomic_read_explicit(&f->change_seq, &seq, memory_order_relaxed);
+ if (seq != port_seq) {
+ port_seq = seq;
break;
}
}
@@ -1806,7 +1807,7 @@ dp_netdev_set_pmd_threads(struct dp_netdev *dp, int n)
f->dp = dp;
f->id = i;
- atomic_store(&f->change_seq, 1);
+ atomic_init(&f->change_seq, PMD_INITIAL_SEQ);
/* Each thread will distribute all devices rx-queues among
* themselves. */
--
1.7.10.4
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