Comment 19 for bug 2056461

Interesting finding: with debug=0x0f the bug is not triggered - I have to reduce the debug flags to trigger it. Currently working up from P9_DEBUG_VFS:

With run #34 and debug=0x08 (P9_DEBUG_VFS) I captured logs (attached). Hang occurs in autopkgtest at timestamp 10:08:37.390685 (UTC+1). In the guest kernel log that maps to timestamp 09:08:37.408129.

The first read on fd 0 is:

09:08:37.481590 v9fs_file_read_iter (1049): fid 6 count 1000000 offset 0

followed by subsequent reads:

09:08:37.517808 v9fs_file_read_iter (1049): fid 6 count 1000000 offset 1000000
...
09:08:37.565864 v9fs_file_read_iter (1049): fid 6 count 1000000 offset 2000000
...
09:08:37.609522 v9fs_file_read_iter (1049): fid 6 count 1000000 offset 3000000
...
09:08:37.653503 v9fs_file_read_iter (1049): fid 6 count 1000000 offset 4000000
...
09:08:37.693647 v9fs_file_read_iter (1049): fid 6 count 1000000 offset 5000000
...
09:08:37.716325 v9fs_file_read_iter (1049): fid 6 count 1000000 offset 5275648

At which point it starts 'spinning' waiting for more data.

On the host we see:

~/tmp/9pfs$ ls -latr autopkgtest-qemu.ngbyoymu/shared/job.mon5m14s/
total 8072
-rw-r--r-- 1 root root 0 2024-05-31 10:08 stdout
-rw-r--r-- 1 root root 0 2024-05-31 10:08 stderr
drwxrwxrwt 3 root root 4096 2024-05-31 10:08 ..
-rwxr-xr-x 1 root root 8253440 2024-05-31 10:08 stdin
-rw-r--r-- 1 root root 7 2024-05-31 10:08 stdin_eof
drwxr-xr-x 2 root root 4096 2024-05-31 10:08 .