[PATCH 18/19] staging: lustre: replace l_wait_event_exclusive_head() with wait_event_idle_exclusive

NeilBrown
2018-01-08T03:31:26Z

This l_wait_event_exclusive_head() will wait indefinitely
if the timeout is zero. If it does wait with a timeout
and times out, the timeout for next time is set to zero.

The can be mapped to a call to either
wait_event_idle_exclusive()
or
wait_event_idle_exclusive_timeout()
depending in the timeout setting.

The current code arrange for LIFO queuing of waiters,
but include/event.h doesn't support that yet.
Until it does, fall back on FIFO with
wait_event_idle_exclusive{,_timeout}().

Signed-off-by: NeilBrown <neilb@suse.com>
---
drivers/staging/lustre/lustre/ptlrpc/service.c | 43 ++++++++++++++----------
1 file changed, 25 insertions(+), 18 deletions(-)

diff --git a/drivers/staging/lustre/lustre/ptlrpc/service.c b/drivers/staging/lustre/lustre/ptlrpc/service.c
index 6e3403417434..29fdb54f16ca 100644
--- a/drivers/staging/lustre/lustre/ptlrpc/service.c
+++ b/drivers/staging/lustre/lustre/ptlrpc/service.c
@@ -1897,15 +1897,6 @@ ptlrpc_check_rqbd_pool(struct ptlrpc_service_part *svcpt)
}
}

-static int
-ptlrpc_retry_rqbds(void *arg)
-{
- struct ptlrpc_service_part *svcpt = arg;
-
- svcpt->scp_rqbd_timeout = 0;
- return -ETIMEDOUT;
-}
-
static inline int
ptlrpc_threads_enough(struct ptlrpc_service_part *svcpt)
{
@@ -1968,13 +1959,17 @@ ptlrpc_server_request_incoming(struct ptlrpc_service_part *svcpt)
return !list_empty(&svcpt->scp_req_incoming);
}

+/* We perfer lifo queuing, but kernel doesn't provide that yet. */
+#ifndef wait_event_idle_exclusive_lifo
+#define wait_event_idle_exclusive_lifo wait_event_idle_exclusive
+#define wait_event_idle_exclusive_lifo_timeout wait_event_idle_exclusive_timeout
+#endif
+
static __attribute__((__noinline__)) int
ptlrpc_wait_event(struct ptlrpc_service_part *svcpt,
struct ptlrpc_thread *thread)
{
/* Don't exit while there are replies to be handled */
- struct l_wait_info lwi = LWI_TIMEOUT(svcpt->scp_rqbd_timeout,
- ptlrpc_retry_rqbds, svcpt);

/* XXX: Add this back when libcfs watchdog is merged upstream
lc_watchdog_disable(thread->t_watchdog);
@@ -1982,13 +1977,25 @@ ptlrpc_wait_event(struct ptlrpc_service_part *svcpt,

cond_resched();

- l_wait_event_exclusive_head(svcpt->scp_waitq,
- ptlrpc_thread_stopping(thread) ||
- ptlrpc_server_request_incoming(svcpt) ||
- ptlrpc_server_request_pending(svcpt,
- false) ||
- ptlrpc_rqbd_pending(svcpt) ||
- ptlrpc_at_check(svcpt), &lwi);
+ if (svcpt->scp_rqbd_timeout == 0)
+ wait_event_idle_exclusive_lifo(
+ svcpt->scp_waitq,
+ ptlrpc_thread_stopping(thread) ||
+ ptlrpc_server_request_incoming(svcpt) ||
+ ptlrpc_server_request_pending(svcpt,
+ false) ||
+ ptlrpc_rqbd_pending(svcpt) ||
+ ptlrpc_at_check(svcpt));
+ else if (0 == wait_event_idle_exclusive_lifo_timeout(
+ svcpt->scp_waitq,
+ ptlrpc_thread_stopping(thread) ||
+ ptlrpc_server_request_incoming(svcpt) ||
+ ptlrpc_server_request_pending(svcpt,
+ false) ||
+ ptlrpc_rqbd_pending(svcpt) ||
+ ptlrpc_at_check(svcpt),
+ svcpt->scp_rqbd_timeout))
+ svcpt->scp_rqbd_timeout = 0;

if (ptlrpc_thread_stopping(thread))
return -EINTR;