io-wq: ensure we have a stable view of ->cur_work for cancellations
to #26323578 commit 36c2f9223e84c1aa84bfba90cb2e74b517c92a54 upstream. worker->cur_work is currently protected by the lock of the wqe that the worker belongs to. When we send a signal to a worker, we need a stable view of ->cur_work, so we need to hold that lock. But this doesn't work so well, since we have the opposite order potentially on queueing work. If POLL_ADD is used with a signalfd, then io_poll_wake() is called with the signal lock, and that sometimes needs to insert work items. Add a specific worker lock that protects the current work item. Then we can guarantee that the task we're sending a signal is currently processing the exact work we think it is. Reported-by: NPaul E. McKenney <paulmck@kernel.org> Reviewed-by: NPaul E. McKenney <paulmck@kernel.org> Signed-off-by: NJens Axboe <axboe@kernel.dk> Signed-off-by: NJoseph Qi <joseph.qi@linux.alibaba.com> Acked-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
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