On Sat, 2025-02-01 at 15:00 -0500, trondmy@xxxxxxxxxx wrote:
> From: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
>
> 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: Li Lingfeng <lilingfeng3@xxxxxxxxxx>
> Fixes: 39494194f93b ("SUNRPC: Fix races with rpc_killall_tasks()")
> Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> ---
> include/linux/sunrpc/sched.h | 3 +--
> include/trace/events/sunrpc.h | 3 +--
> net/sunrpc/sched.c | 2 --
> 3 files changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/include/linux/sunrpc/sched.h b/include/linux/sunrpc/sched.h
> index fec1e8a1570c..eac57914dcf3 100644
> --- a/include/linux/sunrpc/sched.h
> +++ b/include/linux/sunrpc/sched.h
> @@ -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.
> diff --git a/include/trace/events/sunrpc.h b/include/trace/events/sunrpc.h
> index b13dc275ef4a..851841336ee6 100644
> --- a/include/trace/events/sunrpc.h
> +++ b/include/trace/events/sunrpc.h
> @@ -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,
>
> diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
> index cef623ea1506..9b45fbdc90ca 100644
> --- a/net/sunrpc/sched.c
> +++ b/net/sunrpc/sched.c
> @@ -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);
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
