A problem reported when attaching GDB to programs that use io_uring has led to a flurry of potential
solutions, and one that was merged into Linux 5.12-rc5. The problem
stemmed from a change made in the 5.12
merge window to
how the threads used by io_uring were created, such that they became associated
with the process using io_uring. Those “I/O threads” were treated
specially in the kernel, but that led to the problem with GDB (and likely other ptrace()-using
programs). The solution is to treat them like other threads because it
turned out that trying to make
them special caused more problems than it solved.

Source: LWN.net – [$] GDB and io_uring