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lib/dpif-netdev: Clean-up pmd thread signaling.

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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 <jrajahalme@nicira.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
This commit is contained in:
Jarno Rajahalme
2014-08-15 15:09:38 -07:00
parent a6f4ad08d3
commit 84067a4c1a
1 changed files with 14 additions and 13 deletions
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27
lib/dpif-netdev.c
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@@ -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) {
unsigned int seq;
lc = 0;
ovsrcu_quiesce();
/* 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) {
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. */