On 5/5/21 5:03 AM, Stefan Metzmacher wrote: > As io_threads are fully set up USER threads it's clearer to > separate the code path from the KTHREAD logic. > > The only remaining difference to user space threads is that > io_threads never return to user space again. > Instead they loop within the given worker function. > > The fact that they never return to user space means they > don't have an user space thread stack. In order to > indicate that to tools like gdb we reset the stack and instruction > pointers to 0. > > This allows gdb attach to user space processes using io-uring, > which like means that they have io_threads, without printing worrying > message like this: > > warning: Selected architecture i386:x86-64 is not compatible with reported target architecture i386 > > warning: Architecture rejected target-supplied description > > The output will be something like this: > > (gdb) info threads > Id Target Id Frame > * 1 LWP 4863 "io_uring-cp-for" syscall () at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38 > 2 LWP 4864 "iou-mgr-4863" 0x0000000000000000 in ?? () > 3 LWP 4865 "iou-wrk-4863" 0x0000000000000000 in ?? () > (gdb) thread 3 > [Switching to thread 3 (LWP 4865)] > #0 0x0000000000000000 in ?? () > (gdb) bt > #0 0x0000000000000000 in ?? () > Backtrace stopped: Cannot access memory at address 0x0 I have queued this one up in the io_uring branch, also happy to drop it if the x86 folks want to take it instead. Let me know! -- Jens Axboe
