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ovs/tests/test-rcu.c

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ovs-thread: Do not always end quiescent state in ovs_thread_create(). A new thread must be started in a non quiescent state. There is a call to ovsrcu_quiesce_end() in ovsthread_wrapper(), to enforce this. ovs_thread_create(), instead, is executed in the parent thread. It must call ovsrcu_quiesce_end() on its first invocation, to put the main thread in a non quiescent state. On every other invocation, it doesn't make sense to alter the calling thread state, so this commits wraps the call to ovsrcu_quiesce_end() in an ovsthread_once construct. This fixes a bug in ovs-rcu where the first call in the process to ovsrcu_quiesce_start() will not be honored, because the calling thread will need to create the 'urcu' thread (and creating a thread will wrongly end its quiescent state). ovsrcu_quiesce_start() ovs_rcu_quiesced() if (ovsthread_once_start(&once)) { ovs_thread_create("urcu") /*This will end the quiescent state*/ } This bug affects in particular ovs-vswitchd with DPDK. In the DPDK case the first threads created are "vhost_thread" and "dpdk_watchdog". If dpdk_watchdog is the first to call ovsrcu_quiesce_start() (via xsleep()), the call is not honored and the RCU grace period lasts at least for DPDK_PORT_WATCHDOG_INTERVAL (5s on current master). If vhost_thread, on the other hand, is the first to call ovsrcu_quiesce_start(), the call is not honored and the RCU grace period lasts undefinitely, because no more calls to ovsrcu_quiesce_start() are issued from vhost_thread. For some reason (it's a race condition after all), on current master, dpdk_watchdog will always be the first to call ovsrcu_quiesce_start(), but with the upcoming DPDK database configuration changes, sometimes vhost_thread will issue the first call to ovsrcu_quiesce_start(). Sample ovs-vswitchd.log: 2016-03-23T22:34:28.532Z|00004|ovs_rcu(urcu3)|WARN|blocked 8000 ms waiting for vhost_thread2 to quiesce 2016-03-23T22:34:30.501Z|00118|ovs_rcu|WARN|blocked 8000 ms waiting for vhost_thread2 to quiesce 2016-03-23T22:34:36.532Z|00005|ovs_rcu(urcu3)|WARN|blocked 16000 ms waiting for vhost_thread2 to quiesce 2016-03-23T22:34:38.501Z|00119|ovs_rcu|WARN|blocked 16000 ms waiting for vhost_thread2 to quiesce The commit also adds a test for the ovs-rcu module to make sure that: * A new thread is started in a non quiescent state. * The first call to ovsrcu_quiesce_start() is honored. * When a process becomes multithreaded the main thread is put in an active state Signed-off-by: Daniele Di Proietto <diproiettod@vmware.com> Acked-by: Ben Pfaff <blp@ovn.org>
2016-03-23 16:37:47 -07:00
/*
* Copyright (c) 2016 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#undef NDEBUG
#include "fatal-signal.h"
#include "ovs-rcu.h"
#include "ovs-thread.h"
#include "ovstest.h"
#include "util.h"
static void *
quiescer_main(void *aux OVS_UNUSED)
{
/* A new thread must be not be quiescent */
ovs_assert(!ovsrcu_is_quiescent());
ovsrcu_quiesce_start();
/* After the above call it must be quiescent */
ovs_assert(ovsrcu_is_quiescent());
return NULL;
}
static void
test_rcu_quiesce(void)
ovs-thread: Do not always end quiescent state in ovs_thread_create(). A new thread must be started in a non quiescent state. There is a call to ovsrcu_quiesce_end() in ovsthread_wrapper(), to enforce this. ovs_thread_create(), instead, is executed in the parent thread. It must call ovsrcu_quiesce_end() on its first invocation, to put the main thread in a non quiescent state. On every other invocation, it doesn't make sense to alter the calling thread state, so this commits wraps the call to ovsrcu_quiesce_end() in an ovsthread_once construct. This fixes a bug in ovs-rcu where the first call in the process to ovsrcu_quiesce_start() will not be honored, because the calling thread will need to create the 'urcu' thread (and creating a thread will wrongly end its quiescent state). ovsrcu_quiesce_start() ovs_rcu_quiesced() if (ovsthread_once_start(&once)) { ovs_thread_create("urcu") /*This will end the quiescent state*/ } This bug affects in particular ovs-vswitchd with DPDK. In the DPDK case the first threads created are "vhost_thread" and "dpdk_watchdog". If dpdk_watchdog is the first to call ovsrcu_quiesce_start() (via xsleep()), the call is not honored and the RCU grace period lasts at least for DPDK_PORT_WATCHDOG_INTERVAL (5s on current master). If vhost_thread, on the other hand, is the first to call ovsrcu_quiesce_start(), the call is not honored and the RCU grace period lasts undefinitely, because no more calls to ovsrcu_quiesce_start() are issued from vhost_thread. For some reason (it's a race condition after all), on current master, dpdk_watchdog will always be the first to call ovsrcu_quiesce_start(), but with the upcoming DPDK database configuration changes, sometimes vhost_thread will issue the first call to ovsrcu_quiesce_start(). Sample ovs-vswitchd.log: 2016-03-23T22:34:28.532Z|00004|ovs_rcu(urcu3)|WARN|blocked 8000 ms waiting for vhost_thread2 to quiesce 2016-03-23T22:34:30.501Z|00118|ovs_rcu|WARN|blocked 8000 ms waiting for vhost_thread2 to quiesce 2016-03-23T22:34:36.532Z|00005|ovs_rcu(urcu3)|WARN|blocked 16000 ms waiting for vhost_thread2 to quiesce 2016-03-23T22:34:38.501Z|00119|ovs_rcu|WARN|blocked 16000 ms waiting for vhost_thread2 to quiesce The commit also adds a test for the ovs-rcu module to make sure that: * A new thread is started in a non quiescent state. * The first call to ovsrcu_quiesce_start() is honored. * When a process becomes multithreaded the main thread is put in an active state Signed-off-by: Daniele Di Proietto <diproiettod@vmware.com> Acked-by: Ben Pfaff <blp@ovn.org>
2016-03-23 16:37:47 -07:00
{
pthread_t quiescer;
quiescer = ovs_thread_create("quiescer", quiescer_main, NULL);
/* This is the main thread of the process. After spawning its first
* thread it must not be quiescent. */
ovs_assert(!ovsrcu_is_quiescent());
xpthread_join(quiescer, NULL);
}
static void
add_count(void *_count)
{
unsigned *count = (unsigned *)_count;
(*count) ++;
}
static void
test_rcu_barrier(void)
{
unsigned count = 0;
for (int i = 0; i < 10; i ++) {
ovsrcu_postpone(add_count, &count);
}
ovsrcu_barrier();
ovs_assert(count == 10);
}
static void
test_rcu(int argc OVS_UNUSED, char *argv[] OVS_UNUSED) {
test_rcu_quiesce();
test_rcu_barrier();
}
OVSTEST_REGISTER("test-rcu", test_rcu);