[PATCH 11/17] staging: lustre: ptlrpc: use workqueue for pinger

From: NeilBrown
Date: Thu Mar 01 2018 - 18:33:43 EST


lustre has a "Pinger" kthread which periodically pings peers
to ensure all hosts are functioning.

This can more easily be done using a work queue.

As maintaining contact with other peers is import for
keeping the filesystem running, and as the filesystem might
be involved in freeing memory, it is safest to have a
separate WQ_MEM_RECLAIM workqueue.

The SVC_EVENT functionality to wake up the thread can be
replaced with mod_delayed_work().

Also use round_jiffies_up_relative() rather than setting a
minimum of 1 second delay. The PING_INTERVAL is measured in
seconds so this meets the need is allow the workqueue to
keep wakeups synchronized.

Signed-off-by: NeilBrown <neilb@xxxxxxxx>
---
drivers/staging/lustre/lustre/ptlrpc/pinger.c | 81 +++++++------------------
1 file changed, 24 insertions(+), 57 deletions(-)

diff --git a/drivers/staging/lustre/lustre/ptlrpc/pinger.c b/drivers/staging/lustre/lustre/ptlrpc/pinger.c
index b5f3cfee8e75..0775b7a048bb 100644
--- a/drivers/staging/lustre/lustre/ptlrpc/pinger.c
+++ b/drivers/staging/lustre/lustre/ptlrpc/pinger.c
@@ -217,21 +217,18 @@ static void ptlrpc_pinger_process_import(struct obd_import *imp,
}
}

-static int ptlrpc_pinger_main(void *arg)
-{
- struct ptlrpc_thread *thread = arg;
-
- /* Record that the thread is running */
- thread_set_flags(thread, SVC_RUNNING);
- wake_up(&thread->t_ctl_waitq);
+static struct workqueue_struct *pinger_wq;
+static void ptlrpc_pinger_main(struct work_struct *ws);
+static DECLARE_DELAYED_WORK(ping_work, ptlrpc_pinger_main);

- /* And now, loop forever, pinging as needed. */
- while (1) {
- unsigned long this_ping = cfs_time_current();
- long time_to_next_wake;
- struct timeout_item *item;
- struct obd_import *imp;
+static void ptlrpc_pinger_main(struct work_struct *ws)
+{
+ unsigned long this_ping = cfs_time_current();
+ long time_to_next_wake;
+ struct timeout_item *item;
+ struct obd_import *imp;

+ do {
mutex_lock(&pinger_mutex);
list_for_each_entry(item, &timeout_list, ti_chain) {
item->ti_cb(item, item->ti_cb_data);
@@ -260,50 +257,24 @@ static int ptlrpc_pinger_main(void *arg)
time_to_next_wake,
cfs_time_add(this_ping,
PING_INTERVAL * HZ));
- if (time_to_next_wake > 0) {
- wait_event_idle_timeout(thread->t_ctl_waitq,
- thread_is_stopping(thread) ||
- thread_is_event(thread),
- max_t(long, time_to_next_wake, HZ));
- if (thread_test_and_clear_flags(thread, SVC_STOPPING))
- break;
- /* woken after adding import to reset timer */
- thread_test_and_clear_flags(thread, SVC_EVENT);
- }
- }
+ } while (time_to_next_wake <= 0);

- thread_set_flags(thread, SVC_STOPPED);
- wake_up(&thread->t_ctl_waitq);
-
- CDEBUG(D_NET, "pinger thread exiting, process %d\n", current_pid());
- return 0;
+ queue_delayed_work(pinger_wq, &ping_work,
+ round_jiffies_up_relative(time_to_next_wake));
}

-static struct ptlrpc_thread pinger_thread;
-
int ptlrpc_start_pinger(void)
{
- struct task_struct *task;
- int rc;
-
- if (!thread_is_init(&pinger_thread) &&
- !thread_is_stopped(&pinger_thread))
+ if (pinger_wq)
return -EALREADY;

- init_waitqueue_head(&pinger_thread.t_ctl_waitq);
-
- strcpy(pinger_thread.t_name, "ll_ping");
-
- task = kthread_run(ptlrpc_pinger_main, &pinger_thread,
- pinger_thread.t_name);
- if (IS_ERR(task)) {
- rc = PTR_ERR(task);
- CERROR("cannot start pinger thread: rc = %d\n", rc);
- return rc;
+ pinger_wq = alloc_workqueue("ptlrpc_pinger", WQ_MEM_RECLAIM, 1);
+ if (!pinger_wq) {
+ CERROR("cannot start pinger workqueue\n");
+ return -ENOMEM;
}
- wait_event_idle(pinger_thread.t_ctl_waitq,
- thread_is_running(&pinger_thread));

+ queue_delayed_work(pinger_wq, &ping_work, 0);
return 0;
}

@@ -313,16 +284,13 @@ int ptlrpc_stop_pinger(void)
{
int rc = 0;

- if (thread_is_init(&pinger_thread) ||
- thread_is_stopped(&pinger_thread))
+ if (!pinger_wq)
return -EALREADY;

ptlrpc_pinger_remove_timeouts();
- thread_set_flags(&pinger_thread, SVC_STOPPING);
- wake_up(&pinger_thread.t_ctl_waitq);
-
- wait_event_idle(pinger_thread.t_ctl_waitq,
- thread_is_stopped(&pinger_thread));
+ cancel_delayed_work_sync(&ping_work);
+ destroy_workqueue(pinger_wq);
+ pinger_wq = NULL;

return rc;
}
@@ -505,6 +473,5 @@ static int ptlrpc_pinger_remove_timeouts(void)

void ptlrpc_pinger_wake_up(void)
{
- thread_add_flags(&pinger_thread, SVC_EVENT);
- wake_up(&pinger_thread.t_ctl_waitq);
+ mod_delayed_work(pinger_wq, &ping_work, 0);
}