Olivier Langlois <olivier@xxxxxxxxxxxxxx> writes: > On Mon, 2022-08-22 at 17:16 -0400, Olivier Langlois wrote: >> >> What is stopping the task calling do_coredump() to be interrupted and >> call task_work_add() from the interrupt context? >> >> This is precisely what I was experiencing last summer when I did work >> on this issue. >> >> My understanding of how async I/O works with io_uring is that the >> task >> is added to a wait queue without being put to sleep and when the >> io_uring callback is called from the interrupt context, >> task_work_add() >> is called so that the next time io_uring syscall is invoked, pending >> work is processed to complete the I/O. >> >> So if: >> >> 1. io_uring request is initiated AND the task is in a wait queue >> 2. do_coredump() is called before the I/O is completed >> >> IMHO, this is how you end up having task_work_add() called while the >> coredump is generated. >> > I forgot to add that I have experienced the issue with TCP/IP I/O. > > I suspect that with a TCP socket, the race condition window is much > larger than if it was disk I/O and this might make it easier to > reproduce the issue this way... I was under the apparently mistaken impression that the io_uring task_work_add only comes from the io_uring userspace helper threads. Those are definitely suppressed by my change. Do you have any idea in the code where io_uring code is being called in an interrupt context? I would really like to trace that code path so I have a better grasp on what is happening. If task_work_add is being called from interrupt context then something additional from what I have proposed certainly needs to be done. Eric
