linux-kernel - [PATCH AUTOSEL 5.4 061/330] SUNRPC: Capture completion of all RPC tasks

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Message-Id: <20200918020110.2063155-61-sashal@kernel.org>
Date:   Thu, 17 Sep 2020 21:56:41 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Chuck Lever <chuck.lever@...cle.com>,
        Trond Myklebust <trond.myklebust@...merspace.com>,
        Sasha Levin <sashal@...nel.org>, linux-nfs@...r.kernel.org,
        netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.4 061/330] SUNRPC: Capture completion of all RPC tasks

From: Chuck Lever <chuck.lever@...cle.com>

[ Upstream commit a264abad51d8ecb7954a2f6d9f1885b38daffc74 ]

RPC tasks on the backchannel never invoke xprt_complete_rqst(), so
there is no way to report their tk_status at completion. Also, any
RPC task that exits via rpc_exit_task() before it is replied to will
also disappear without a trace.

Introduce a trace point that is symmetrical with rpc_task_begin that
captures the termination status of each RPC task.

Sample trace output for callback requests initiated on the server:
   kworker/u8:12-448   [003]   127.025240: rpc_task_end:         task:50@3 flags=ASYNC|DYNAMIC|SOFT|SOFTCONN|SENT runstate=RUNNING|ACTIVE status=0 action=rpc_exit_task
   kworker/u8:12-448   [002]   127.567310: rpc_task_end:         task:51@3 flags=ASYNC|DYNAMIC|SOFT|SOFTCONN|SENT runstate=RUNNING|ACTIVE status=0 action=rpc_exit_task
   kworker/u8:12-448   [001]   130.506817: rpc_task_end:         task:52@3 flags=ASYNC|DYNAMIC|SOFT|SOFTCONN|SENT runstate=RUNNING|ACTIVE status=0 action=rpc_exit_task

Odd, though, that I never see trace_rpc_task_complete, either in the
forward or backchannel. Should it be removed?

Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@...merspace.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/trace/events/sunrpc.h | 1 +
 net/sunrpc/sched.c            | 1 +
 2 files changed, 2 insertions(+)

diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
index ffa3c51dbb1a0..28df77a948e56 100644
--- a/include/trace/events/sunrpc.h
+++ b/include/trace/events/sunrpc.h
@@ -165,6 +165,7 @@ DECLARE_EVENT_CLASS(rpc_task_running,
 DEFINE_RPC_RUNNING_EVENT(begin);
 DEFINE_RPC_RUNNING_EVENT(run_action);
 DEFINE_RPC_RUNNING_EVENT(complete);
+DEFINE_RPC_RUNNING_EVENT(end);
 
 DECLARE_EVENT_CLASS(rpc_task_queued,
 
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 987c4b1f0b174..9c79548c68474 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -824,6 +824,7 @@ rpc_reset_task_statistics(struct rpc_task *task)
  */
 void rpc_exit_task(struct rpc_task *task)
 {
+	trace_rpc_task_end(task, task->tk_action);
 	task->tk_action = NULL;
 	if (task->tk_ops->rpc_count_stats)
 		task->tk_ops->rpc_count_stats(task, task->tk_calldata);
-- 
2.25.1