Commit 5bbd6e86 authored by Trond Myklebust's avatar Trond Myklebust Committed by Anna Schumaker
Browse files

SUNRPC: Prevent looping due to rpc_signal_task() races 



If rpc_signal_task() is called while a task is in an rpc_call_done()
callback function, and the latter calls rpc_restart_call(), the task can
end up looping due to the RPC_TASK_SIGNALLED flag being set without the
tk_rpc_status being set.
Removing the redundant mechanism for signalling the task fixes the
looping behaviour.

Reported-by: default avatarLi Lingfeng <lilingfeng3@huawei.com>
Fixes: 39494194 ("SUNRPC: Fix races with rpc_killall_tasks()")
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
Reviewed-by: default avatarJeff Layton <jlayton@kernel.org>
Signed-off-by: default avatarAnna Schumaker <anna.schumaker@oracle.com>
parent 88025c67

include/linux/sunrpc/sched.h

+1 −2
Original line number Diff line number Diff line
@@ -158,7 +158,6 @@ enum { 
	RPC_TASK_NEED_XMIT,

	RPC_TASK_NEED_RECV,

	RPC_TASK_MSG_PIN_WAIT,

	RPC_TASK_SIGNALLED,

};



#define rpc_test_and_set_running(t) \
@@ -171,7 +170,7 @@ enum { 


#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)

#define RPC_SIGNALLED(t)	(READ_ONCE(task->tk_rpc_status) == -ERESTARTSYS)



/*

 * Task priorities.

include/trace/events/sunrpc.h

+1 −2
Original line number Diff line number Diff line
@@ -360,8 +360,7 @@ TRACE_EVENT(rpc_request, 
		{ (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_SIGNALLED), "SIGNALLED" })

		{ (1UL << RPC_TASK_MSG_PIN_WAIT), "MSG_PIN_WAIT" })



DECLARE_EVENT_CLASS(rpc_task_running,

net/sunrpc/sched.c

+0 −2
Original line number Diff line number Diff line
@@ -864,8 +864,6 @@ void rpc_signal_task(struct rpc_task *task) 
	if (!rpc_task_set_rpc_status(task, -ERESTARTSYS))

		return;

	trace_rpc_task_signalled(task, task->tk_action);

	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(queue, task);