Jens Axboe <axboe@xxxxxxxxx> writes: > Hi, > > Stefan reports that attaching to a task with io_uring will leave gdb > very confused and just repeatedly attempting to attach to the IO threads, > even though it receives an -EPERM every time. This patchset proposes to > skip PF_IO_WORKER threads as same_thread_group(), except for accounting > purposes which we still desire. > > We also skip listing the IO threads in /proc/<pid>/task/ so that gdb > doesn't think it should stop and attach to them. This makes us consistent > with earlier kernels, where these async threads were not related to the > ring owning task, and hence gdb (and others) ignored them anyway. > > Seems to me that this is the right approach, but open to comments on if > others agree with this. Oleg, I did see your messages as well on SIGSTOP, > and as was discussed with Eric as well, this is something we most > certainly can revisit. I do think that the visibility of these threads > is a separate issue. Even with SIGSTOP implemented (which I did try as > well), we're never going to allow ptrace attach and hence gdb would still > be broken. Hence I'd rather treat them as separate issues to attack. A quick skim shows that these threads are not showing up anywhere in proc which appears to be a problem, as it hides them from top. Sysadmins need the ability to dig into a system and find out where all their cpu usage or io's have gone when there is a problem. I general I think this argues that these threads should show up as threads of the process so I am not even certain this is the right fix to deal with gdb. Eric
