Re: Using SQPOLL for-5.11/io_uring kernel NULL pointer dereference

[Josef <josef.grieb@gmail.com>]

> I haven't got the first email, is it "kernel NULL pointer dereference"
> as in the subject or just freeze?

that's weird..probably the size of the attached log file is too big...
here dmesg log file
https://gist.github.com/1Jo1/3d0bcefc18f097265f0dc1ef054a87c0

> - did you locate which test hangs it? If so what it uses? e.g. SQPOLL
> sharing, IOPOLL., etc.

yes, it uses SQPOLL, without sharing, IPOLL is not enabled, and Async
Flag is enabled

> - is it send/recvmsg, send/recv you use? any other?

no the tests which occurs the error use these operations: OP_READ,
OP_WRITE, OP_POLL_ADD, OP_POLL_REMOVE, OP_CLOSE, OP_ACCEPT, OP_TIMEOUT
(OP_READ, OP_WRITE and OP_CLOSE async flag is enabled)

> - does this happen often?

yeah quite often

> - you may try `funcgraph __io_sq_thread -H` or even with `io_sq_thread`
> (funcgraph is from bpftools). Or catch that with some other tools.

I'm not quite familiar with these tools( kernel debugging in general)
I'll take a look tomorrow


ernel NULL pointer dereference"
> as in the subject or just freeze?
>
> also
> - anything in dmesg? (>5 min after freeze)
> - did you locate which test hangs it? If so what it uses? e.g. SQPOLL
> sharing, IOPOLL., etc.
> - is it send/recvmsg, send/recv you use? any other?
> - does this happen often?
> - you may try `funcgraph __io_sq_thread -H` or even with `io_sq_thread`
> (funcgraph is from bpftools). Or catch that with some other tools.
>
> --
> Pavel Begunkov