On Mon, 2021-05-03 at 20:50 -0600, Jens Axboe wrote: > > I tested the below, which is the two combined, with a case that > deliberately has two types of io threads - one for SQPOLL submission, > and one that was created due to async work being needed. gdb attaches > just fine to the creator, with a slight complaint: > > Attaching to process 370 > [New LWP 371] > [New LWP 372] > Error while reading shared library symbols for > /usr/lib/libpthread.so.0: > Cannot find user-level thread for LWP 372: generic error > 0x00007f1a74675125 in clock_nanosleep@GLIBC_2.2.5 () from > /usr/lib/libc.so.6 > (gdb) info threads > Id Target Id Frame > * 1 LWP 370 "io_uring" 0x00007f1a74675125 in > clock_nanosleep@GLIBC_2.2.5 () > from /usr/lib/libc.so.6 > 2 LWP 371 "iou-sqp-370" 0x00007f1a746a7a9d in syscall () from > /usr/lib/libc.so.6 > 3 LWP 372 "io_uring" 0x00007f1a74675125 in > clock_nanosleep@GLIBC_2.2.5 () > from /usr/lib/libc.so.6 > > (gdb) thread 2 > [Switching to thread 2 (LWP 371)] > #0 0x00007f1a746a7a9d in syscall () from /usr/lib/libc.so.6 > (gdb) bt > #0 0x00007f1a746a7a9d in syscall () from /usr/lib/libc.so.6 > Backtrace stopped: Cannot access memory at address 0x0 > > (gdb) thread 1 > [Switching to thread 1 (LWP 370)] > #0 0x00007f1a74675125 in clock_nanosleep@GLIBC_2.2.5 () from > /usr/lib/libc.so.6 > (gdb) bt > #0 0x00007f1a74675125 in clock_nanosleep@GLIBC_2.2.5 () from > /usr/lib/libc.so.6 > #1 0x00007f1a7467a357 in nanosleep () from /usr/lib/libc.so.6 > #2 0x00007f1a7467a28e in sleep () from /usr/lib/libc.so.6 > #3 0x000055bd41e929ba in main (argc=<optimized out>, argv=<optimized > out>) > at t/io_uring.c:658 > > which looks very reasonable to me - no backtraces for the io threads, > and > no arch complaints. > I have reported an issue that I have with a user process using io_uring where when it core dumps, the dump fails to be generated. https://github.com/axboe/liburing/issues/346 Pavel did comment to my report and he did point out this thread as possibly a related issue. I'm far from being 100% convinced that Stefan patch can help but I am going to give it a try and report back here if it does help. Greetings, Olivier
