Re: Stalls when starting a VSOCK listening socket: soft lockups, RCU stalls, timeout

Thomas Gleixner
2026-03-05T19:25:30Z

On Thu, Mar 05 2026 at 18:33, Jiri Slaby wrote:
> On 05. 03. 26, 17:16, Thomas Gleixner wrote:
>
> ====== PID 7680 (spinning in mm_get_cid()) ======
> 4 tasks with
> mm = 0xffff8cc406824680
> mm_cid.pcpu = 0x66222619df00,
>
>
> crash> task -x -R mm_cid ffff8cc4038525c0 ffff8cc40ad40000
> ffff8cc40683cb80 ffff8cc418424b80
> PID: 7680 TASK: ffff8cc4038525c0 CPU: 1 COMMAND: "asm"
> mm_cid = {
> active = 0x1,
> cid = 0x80000000
> },

So CID 3 has gone AWOL...

> PID: 7681 TASK: ffff8cc40ad40000 CPU: 3 COMMAND: "asm"
> mm_cid = {
> active = 0x1,
> cid = 0x40000000
> },
>
> PID: 7682 TASK: ffff8cc40683cb80 CPU: 0 COMMAND: "asm"
> mm_cid = {
> active = 0x1,
> cid = 0x40000002
> },
>
> PID: 7684 TASK: ffff8cc418424b80 CPU: 2 COMMAND: "asm"
> mm_cid = {
> active = 0x1,
> cid = 0x40000001
> },
>
> crash> struct mm_cid_pcpu -x 0xfffff2e9bfc09f00
> struct mm_cid_pcpu {
> cid = 0x40000002
> }
> crash> struct mm_cid_pcpu -x 0xfffff2e9bfc89f00
> struct mm_cid_pcpu {
> cid = 0x0
> }
> crash> struct mm_cid_pcpu -x 0xfffff2e9bfd09f00
> struct mm_cid_pcpu {
> cid = 0x40000001
> }
> crash> struct mm_cid_pcpu -x 0xfffff2e9bfd89f00
> struct mm_cid_pcpu {
> cid = 0x40000000
> }

... as 0, 1, 2 are owned by CPUs 3, 2, 0.

The other process is not relevant. That's just fallout and has a
different CID space, which is consistent.

Is there simple way to reproduce?

Thanks,

tglx