From:   Trond Myklebust <trondmy@gmail.com>
To:     linux-nfs@vger.kernel.org
Subject: [PATCH v2 01/28] SUNRPC: Fix up task signalling
Date:   Fri, 29 Mar 2019 17:59:21 -0400
Message-Id: <20190329215948.107328-2-trond.myklebust@hammerspace.com>
In-Reply-To: <20190329215948.107328-1-trond.myklebust@hammerspace.com>
References: <20190329215948.107328-1-trond.myklebust@hammerspace.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-nfs-owner@vger.kernel.org
Precedence: bulk

The RPC_TASK_KILLED flag should really not be set from another context
because it can clobber data in the struct task when task->tk_flags is
changed non-atomically.
Let's therefore swap out RPC_TASK_KILLED with an atomic flag, and add
a function to set that flag and safely wake up the task.

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/lockd/clntproc.c           |  4 ++--
 fs/nfsd/nfs4callback.c        |  4 ++--
 include/linux/sunrpc/sched.h  |  6 ++++--
 include/trace/events/sunrpc.h |  6 +++---
 net/sunrpc/clnt.c             | 14 ++------------
 net/sunrpc/sched.c            | 28 +++++++++++++++++++++++-----
 net/sunrpc/xprt.c             |  4 ++++
 7 files changed, 40 insertions(+), 26 deletions(-)

diff --git a/fs/lockd/clntproc.c b/fs/lockd/clntproc.c
index e8a004097d18..d9c32d1a20c0 100644
--- a/fs/lockd/clntproc.c
+++ b/fs/lockd/clntproc.c
@@ -715,7 +715,7 @@ static void nlmclnt_unlock_callback(struct rpc_task *task, void *data)
 	struct nlm_rqst	*req = data;
 	u32 status = ntohl(req->a_res.status);
 
-	if (RPC_ASSASSINATED(task))
+	if (RPC_SIGNALLED(task))
 		goto die;
 
 	if (task->tk_status < 0) {
@@ -783,7 +783,7 @@ static void nlmclnt_cancel_callback(struct rpc_task *task, void *data)
 	struct nlm_rqst	*req = data;
 	u32 status = ntohl(req->a_res.status);
 
-	if (RPC_ASSASSINATED(task))
+	if (RPC_SIGNALLED(task))
 		goto die;
 
 	if (task->tk_status < 0) {
diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
index d219159b98af..f7494be8dbe2 100644
--- a/fs/nfsd/nfs4callback.c
+++ b/fs/nfsd/nfs4callback.c
@@ -1032,7 +1032,7 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback
 		 * the submission code will error out, so we don't need to
 		 * handle that case here.
 		 */
-		if (task->tk_flags & RPC_TASK_KILLED)
+		if (RPC_SIGNALLED(task))
 			goto need_restart;
 
 		return true;
@@ -1081,7 +1081,7 @@ static bool nfsd4_cb_sequence_done(struct rpc_task *task, struct nfsd4_callback
 	dprintk("%s: freed slot, new seqid=%d\n", __func__,
 		clp->cl_cb_session->se_cb_seq_nr);
 
-	if (task->tk_flags & RPC_TASK_KILLED)
+	if (RPC_SIGNALLED(task))
 		goto need_restart;
 out:
 	return ret;
diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
index ec861cd0cfe8..852ca0f2c56c 100644
--- a/include/linux/sunrpc/sched.h
+++ b/include/linux/sunrpc/sched.h
@@ -125,7 +125,6 @@ struct rpc_task_setup {
 #define RPC_CALL_MAJORSEEN	0x0020		/* major timeout seen */
 #define RPC_TASK_ROOTCREDS	0x0040		/* force root creds */
 #define RPC_TASK_DYNAMIC	0x0080		/* task was kmalloc'ed */
-#define RPC_TASK_KILLED		0x0100		/* task was killed */
 #define RPC_TASK_SOFT		0x0200		/* Use soft timeouts */
 #define RPC_TASK_SOFTCONN	0x0400		/* Fail if can't connect */
 #define RPC_TASK_SENT		0x0800		/* message was sent */
@@ -135,7 +134,6 @@ struct rpc_task_setup {
 
 #define RPC_IS_ASYNC(t)		((t)->tk_flags & RPC_TASK_ASYNC)
 #define RPC_IS_SWAPPER(t)	((t)->tk_flags & RPC_TASK_SWAPPER)
-#define RPC_ASSASSINATED(t)	((t)->tk_flags & RPC_TASK_KILLED)
 #define RPC_IS_SOFT(t)		((t)->tk_flags & (RPC_TASK_SOFT|RPC_TASK_TIMEOUT))
 #define RPC_IS_SOFTCONN(t)	((t)->tk_flags & RPC_TASK_SOFTCONN)
 #define RPC_WAS_SENT(t)		((t)->tk_flags & RPC_TASK_SENT)
@@ -146,6 +144,7 @@ struct rpc_task_setup {
 #define RPC_TASK_NEED_XMIT	3
 #define RPC_TASK_NEED_RECV	4
 #define RPC_TASK_MSG_PIN_WAIT	5
+#define RPC_TASK_SIGNALLED	6
 
 #define RPC_IS_RUNNING(t)	test_bit(RPC_TASK_RUNNING, &(t)->tk_runstate)
 #define rpc_set_running(t)	set_bit(RPC_TASK_RUNNING, &(t)->tk_runstate)
@@ -169,6 +168,8 @@ struct rpc_task_setup {
 
 #define RPC_IS_ACTIVATED(t)	test_bit(RPC_TASK_ACTIVE, &(t)->tk_runstate)
 
+#define RPC_SIGNALLED(t)	test_bit(RPC_TASK_SIGNALLED, &(t)->tk_runstate)
+
 /*
  * Task priorities.
  * Note: if you change these, you must also change
@@ -217,6 +218,7 @@ struct rpc_task *rpc_run_task(const struct rpc_task_setup *);
 struct rpc_task *rpc_run_bc_task(struct rpc_rqst *req);
 void		rpc_put_task(struct rpc_task *);
 void		rpc_put_task_async(struct rpc_task *);
+void		rpc_signal_task(struct rpc_task *);
 void		rpc_exit_task(struct rpc_task *);
 void		rpc_exit(struct rpc_task *, int);
 void		rpc_release_calldata(const struct rpc_call_ops *, void *);
diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
index 7e899e635d33..5e3b77d9daa7 100644
--- a/include/trace/events/sunrpc.h
+++ b/include/trace/events/sunrpc.h
@@ -82,7 +82,6 @@ TRACE_DEFINE_ENUM(RPC_TASK_SWAPPER);
 TRACE_DEFINE_ENUM(RPC_CALL_MAJORSEEN);
 TRACE_DEFINE_ENUM(RPC_TASK_ROOTCREDS);
 TRACE_DEFINE_ENUM(RPC_TASK_DYNAMIC);
-TRACE_DEFINE_ENUM(RPC_TASK_KILLED);
 TRACE_DEFINE_ENUM(RPC_TASK_SOFT);
 TRACE_DEFINE_ENUM(RPC_TASK_SOFTCONN);
 TRACE_DEFINE_ENUM(RPC_TASK_SENT);
@@ -97,7 +96,6 @@ TRACE_DEFINE_ENUM(RPC_TASK_NO_RETRANS_TIMEOUT);
 		{ RPC_CALL_MAJORSEEN, "MAJORSEEN" },			\
 		{ RPC_TASK_ROOTCREDS, "ROOTCREDS" },			\
 		{ RPC_TASK_DYNAMIC, "DYNAMIC" },			\
-		{ RPC_TASK_KILLED, "KILLED" },				\
 		{ RPC_TASK_SOFT, "SOFT" },				\
 		{ RPC_TASK_SOFTCONN, "SOFTCONN" },			\
 		{ RPC_TASK_SENT, "SENT" },				\
@@ -111,6 +109,7 @@ TRACE_DEFINE_ENUM(RPC_TASK_ACTIVE);
 TRACE_DEFINE_ENUM(RPC_TASK_NEED_XMIT);
 TRACE_DEFINE_ENUM(RPC_TASK_NEED_RECV);
 TRACE_DEFINE_ENUM(RPC_TASK_MSG_PIN_WAIT);
+TRACE_DEFINE_ENUM(RPC_TASK_SIGNALLED);
 
 #define rpc_show_runstate(flags)					\
 	__print_flags(flags, "|",					\
@@ -119,7 +118,8 @@ TRACE_DEFINE_ENUM(RPC_TASK_MSG_PIN_WAIT);
 		{ (1UL << RPC_TASK_ACTIVE), "ACTIVE" },			\
 		{ (1UL << RPC_TASK_NEED_XMIT), "NEED_XMIT" },		\
 		{ (1UL << RPC_TASK_NEED_RECV), "NEED_RECV" },		\
-		{ (1UL << RPC_TASK_MSG_PIN_WAIT), "MSG_PIN_WAIT" })
+		{ (1UL << RPC_TASK_MSG_PIN_WAIT), "MSG_PIN_WAIT" },	\
+		{ (1UL << RPC_TASK_SIGNALLED), "SIGNALLED" })
 
 DECLARE_EVENT_CLASS(rpc_task_running,
 
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index 187d10443a15..30f5995c6a68 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -827,14 +827,8 @@ void rpc_killall_tasks(struct rpc_clnt *clnt)
 	 * Spin lock all_tasks to prevent changes...
 	 */
 	spin_lock(&clnt->cl_lock);
-	list_for_each_entry(rovr, &clnt->cl_tasks, tk_task) {
-		if (!RPC_IS_ACTIVATED(rovr))
-			continue;
-		if (!(rovr->tk_flags & RPC_TASK_KILLED)) {
-			rovr->tk_flags |= RPC_TASK_KILLED;
-			rpc_exit(rovr, -EIO);
-		}
-	}
+	list_for_each_entry(rovr, &clnt->cl_tasks, tk_task)
+		rpc_signal_task(rovr);
 	spin_unlock(&clnt->cl_lock);
 }
 EXPORT_SYMBOL_GPL(rpc_killall_tasks);
@@ -1477,8 +1471,6 @@ EXPORT_SYMBOL_GPL(rpc_force_rebind);
 int
 rpc_restart_call_prepare(struct rpc_task *task)
 {
-	if (RPC_ASSASSINATED(task))
-		return 0;
 	task->tk_action = call_start;
 	task->tk_status = 0;
 	if (task->tk_ops->rpc_call_prepare != NULL)
@@ -1494,8 +1486,6 @@ EXPORT_SYMBOL_GPL(rpc_restart_call_prepare);
 int
 rpc_restart_call(struct rpc_task *task)
 {
-	if (RPC_ASSASSINATED(task))
-		return 0;
 	task->tk_action = call_start;
 	task->tk_status = 0;
 	return 1;
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index 28956c70100a..3d6cb91ba598 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -759,8 +759,7 @@ static void
 rpc_reset_task_statistics(struct rpc_task *task)
 {
 	task->tk_timeouts = 0;
-	task->tk_flags &= ~(RPC_CALL_MAJORSEEN|RPC_TASK_KILLED|RPC_TASK_SENT);
-
+	task->tk_flags &= ~(RPC_CALL_MAJORSEEN|RPC_TASK_SENT);
 	rpc_init_task_statistics(task);
 }
 
@@ -773,7 +772,6 @@ void rpc_exit_task(struct rpc_task *task)
 	if (task->tk_ops->rpc_call_done != NULL) {
 		task->tk_ops->rpc_call_done(task, task->tk_calldata);
 		if (task->tk_action != NULL) {
-			WARN_ON(RPC_ASSASSINATED(task));
 			/* Always release the RPC slot and buffer memory */
 			xprt_release(task);
 			rpc_reset_task_statistics(task);
@@ -781,6 +779,19 @@ void rpc_exit_task(struct rpc_task *task)
 	}
 }
 
+void rpc_signal_task(struct rpc_task *task)
+{
+	struct rpc_wait_queue *queue;
+
+	if (!RPC_IS_ACTIVATED(task))
+		return;
+	set_bit(RPC_TASK_SIGNALLED, &task->tk_runstate);
+	smp_mb__after_atomic();
+	queue = READ_ONCE(task->tk_waitqueue);
+	if (queue)
+		rpc_wake_up_queued_task_set_status(queue, task, -ERESTARTSYS);
+}
+
 void rpc_exit(struct rpc_task *task, int status)
 {
 	task->tk_status = status;
@@ -836,6 +847,13 @@ static void __rpc_execute(struct rpc_task *task)
 		 */
 		if (!RPC_IS_QUEUED(task))
 			continue;
+
+		/*
+		 * Signalled tasks should exit rather than sleep.
+		 */
+		if (RPC_SIGNALLED(task))
+			rpc_exit(task, -ERESTARTSYS);
+
 		/*
 		 * The queue->lock protects against races with
 		 * rpc_make_runnable().
@@ -861,7 +879,7 @@ static void __rpc_execute(struct rpc_task *task)
 		status = out_of_line_wait_on_bit(&task->tk_runstate,
 				RPC_TASK_QUEUED, rpc_wait_bit_killable,
 				TASK_KILLABLE);
-		if (status == -ERESTARTSYS) {
+		if (status < 0) {
 			/*
 			 * When a sync task receives a signal, it exits with
 			 * -ERESTARTSYS. In order to catch any callbacks that
@@ -869,7 +887,7 @@ static void __rpc_execute(struct rpc_task *task)
 			 * break the loop here, but go around once more.
 			 */
 			dprintk("RPC: %5u got signal\n", task->tk_pid);
-			task->tk_flags |= RPC_TASK_KILLED;
+			set_bit(RPC_TASK_SIGNALLED, &task->tk_runstate);
 			rpc_exit(task, -ERESTARTSYS);
 		}
 		dprintk("RPC: %5u sync task resuming\n", task->tk_pid);
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index d7117d241460..3a4156cb0134 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1337,6 +1337,10 @@ xprt_request_transmit(struct rpc_rqst *req, struct rpc_task *snd_task)
 			if (status < 0)
 				goto out_dequeue;
 		}
+		if (RPC_SIGNALLED(task)) {
+			status = -ERESTARTSYS;
+			goto out_dequeue;
+		}
 	}
 
 	/*
-- 
2.20.1