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io_uring: don't gate task_work run on TIF_NOTIFY_SIGNAL
This isn't a reliable mechanism to tell if we have task_work pending, we really should be looking at whether we have any items queued. This is problematic if forward progress is gated on running said task_work. One such example is reading from a pipe, where the write side has been closed right before the read is started. The fput() of the file queues TWA_RESUME task_work, and we need that task_work to be run before ->release() is called for the pipe. If ->release() isn't called, then the read will sit forever waiting on data that will never arise. Fix this by io_run_task_work() so it checks if we have task_work pending rather than rely on TIF_NOTIFY_SIGNAL for that. The latter obviously doesn't work for task_work that is queued without TWA_SIGNAL. Reported-by: Christiano Haesbaert <haesbaert@haesbaert.org> Cc: stable@vger.kernel.org Link: https://github.com/axboe/liburing/issues/665 Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -231,11 +231,11 @@ static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)
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static inline int io_run_task_work(void)
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{
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if (test_thread_flag(TIF_NOTIFY_SIGNAL)) {
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if (task_work_pending(current)) {
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if (test_thread_flag(TIF_NOTIFY_SIGNAL))
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clear_notify_signal();
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__set_current_state(TASK_RUNNING);
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clear_notify_signal();
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if (task_work_pending(current))
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task_work_run();
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task_work_run();
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return 1;
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}
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