Jens Axboe <axboe@xxxxxxxxx> 于2025年4月23日周三 23:55写道：
>
> Something like this, perhaps - it'll ensure that io-wq workers get a
> chance to flush out pending work, which should prevent the looping. I've
> attached a basic test case. It'll issue a write that will fault, and
> then try and cancel that as a way to trigger the TIF_NOTIFY_SIGNAL based
> looping.
>
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index d80f94346199..e18926dbf20a 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -32,6 +32,7 @@
> #include <linux/swapops.h>
> #include <linux/miscdevice.h>
> #include <linux/uio.h>
> +#include <linux/io_uring.h>
>
> static int sysctl_unprivileged_userfaultfd __read_mostly;
>
> @@ -376,6 +377,8 @@ vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
> */
> if (current->flags & (PF_EXITING|PF_DUMPCORE))
> goto out;
> + else if (current->flags & PF_IO_WORKER)
> + io_worker_fault();
>
> assert_fault_locked(vmf);
>
> diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
> index 85fe4e6b275c..d93dd7402a28 100644
> --- a/include/linux/io_uring.h
> +++ b/include/linux/io_uring.h
> @@ -28,6 +28,7 @@ static inline void io_uring_free(struct task_struct *tsk)
> if (tsk->io_uring)
> __io_uring_free(tsk);
> }
> +void io_worker_fault(void);
> #else
> static inline void io_uring_task_cancel(void)
> {
> @@ -46,6 +47,9 @@ static inline bool io_is_uring_fops(struct file *file)
> {
> return false;
> }
> +static inline void io_worker_fault(void)
> +{
> +}
> #endif
>
> #endif
> diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
> index d52069b1177b..f74bea028ec7 100644
> --- a/io_uring/io-wq.c
> +++ b/io_uring/io-wq.c
> @@ -1438,3 +1438,13 @@ static __init int io_wq_init(void)
> return 0;
> }
> subsys_initcall(io_wq_init);
> +
> +void io_worker_fault(void)
> +{
> + if (test_thread_flag(TIF_NOTIFY_SIGNAL))
> + clear_notify_signal();
> + if (test_thread_flag(TIF_NOTIFY_RESUME))
> + resume_user_mode_work(NULL);
> + if (task_work_pending(current))
> + task_work_run();
> +}
>
> --
> Jens Axboe
I understand some of what you said. I was indeed lost in appearances.
It's very late here now, and I'll take a deeper look tomorrow.
Thank you very much.
