diff options
| -rw-r--r-- | io_uring/poll.c | 29 |
1 files changed, 17 insertions, 12 deletions
diff --git a/io_uring/poll.c b/io_uring/poll.c index 0d9f49c575e0..97c214aa688c 100644 --- a/io_uring/poll.c +++ b/io_uring/poll.c @@ -394,7 +394,8 @@ static int io_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync, return 1; } -static void io_poll_double_prepare(struct io_kiocb *req) +/* fails only when polling is already completing by the first entry */ +static bool io_poll_double_prepare(struct io_kiocb *req) { struct wait_queue_head *head; struct io_poll *poll = io_poll_get_single(req); @@ -403,20 +404,20 @@ static void io_poll_double_prepare(struct io_kiocb *req) rcu_read_lock(); head = smp_load_acquire(&poll->head); /* - * poll arm may not hold ownership and so race with - * io_poll_wake() by modifying req->flags. There is only one - * poll entry queued, serialise with it by taking its head lock. + * poll arm might not hold ownership and so race for req->flags with + * io_poll_wake(). There is only one poll entry queued, serialise with + * it by taking its head lock. As we're still arming the tw hanlder + * is not going to be run, so there are no races with it. */ - if (head) + if (head) { spin_lock_irq(&head->lock); - - req->flags |= REQ_F_DOUBLE_POLL; - if (req->opcode == IORING_OP_POLL_ADD) - req->flags |= REQ_F_ASYNC_DATA; - - if (head) + req->flags |= REQ_F_DOUBLE_POLL; + if (req->opcode == IORING_OP_POLL_ADD) + req->flags |= REQ_F_ASYNC_DATA; spin_unlock_irq(&head->lock); + } rcu_read_unlock(); + return !!head; } static void __io_queue_proc(struct io_poll *poll, struct io_poll_table *pt, @@ -454,7 +455,11 @@ static void __io_queue_proc(struct io_poll *poll, struct io_poll_table *pt, /* mark as double wq entry */ wqe_private |= IO_WQE_F_DOUBLE; io_init_poll_iocb(poll, first->events, first->wait.func); - io_poll_double_prepare(req); + if (!io_poll_double_prepare(req)) { + /* the request is completing, just back off */ + kfree(poll); + return; + } *poll_ptr = poll; } else { /* fine to modify, there is no poll queued to race with us */ |