From f9c7f26879234395c43d103c191e2dc80ef468dd Mon Sep 17 00:00:00 2001 From: Zhang Xiaoxu Date: Sat, 26 Jun 2021 15:50:42 +0800 Subject: [PATCH] SUNRPC: Should wake up the privileged task firstly. commit 5483b904bf336948826594610af4c9bbb0d9e3aa upstream. When find a task from wait queue to wake up, a non-privileged task may be found out, rather than the privileged. This maybe lead a deadlock same as commit dfe1fe75e00e ("NFSv4: Fix deadlock between nfs4_evict_inode() and nfs4_opendata_get_inode()"): Privileged delegreturn task is queued to privileged list because all the slots are assigned. If there has no enough slot to wake up the non-privileged batch tasks(session less than 8 slot), then the privileged delegreturn task maybe lost waked up because the found out task can't get slot since the session is on draining. So we should treate the privileged task as the emergency task, and execute it as for as we can. Reported-by: Hulk Robot Fixes: 5fcdfacc01f3 ("NFSv4: Return delegations synchronously in evict_inode") Cc: stable@vger.kernel.org Signed-off-by: Zhang Xiaoxu Signed-off-by: Trond Myklebust Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/sched.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index b8be7660b29a..8fc4a6b3422f 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -613,6 +613,15 @@ static struct rpc_task *__rpc_find_next_queued_priority(struct rpc_wait_queue *q struct list_head *q; struct rpc_task *task; + /* + * Service the privileged queue. + */ + q = &queue->tasks[RPC_NR_PRIORITY - 1]; + if (queue->maxpriority > RPC_PRIORITY_PRIVILEGED && !list_empty(q)) { + task = list_first_entry(q, struct rpc_task, u.tk_wait.list); + goto out; + } + /* * Service a batch of tasks from a single owner. */