This reverts commit 4db4b1a0d1779dc159f7b87feb97030ec0b12597.

The IO threads allow and handle SIGSTOP now, so don't special case them
anymore in task_set_jobctl_pending().

Signed-off-by: Jens Axboe <axboe@kernel.dk>

This reverts commit 6fb8f43cede0e4bd3ead847de78d531424a96be9.

The IO threads do allow signals now, including SIGSTOP, and we can allow
ptrace attach. Attaching won't reveal anything interesting for the IO
threads, but it will allow eg gdb to attach to a task with io_urings
and IO threads without complaining. And once attached, it will allow
the usual introspection into regular threads.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

This reverts commit 5be28c8f85ce99ed2d329d2ad8bdd18ea19473a5.

IO threads now take signals just fine, so there's no reason to limit them
specifically. Revert the change that prevented that from happening.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Right now we're never calling get_signal() from PF_IO_WORKER threads, but
in preparation for doing so, don't handle a fatal signal for them. The
workers have state they need to cleanup when exiting, so just return
instead of calling do_exit() on their behalf. The threads themselves will
detect a fatal signal and do proper shutdown.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Just like we don't allow normal signals to IO threads, don't deliver a
STOP to a task that has PF_IO_WORKER set. The IO threads don't take
signals in general, and have no means of flushing out a stop either.

Longer term, we may want to look into allowing stop of these threads,
as it relates to eg process freezing. For now, this prevents a spin
issue if a SIGSTOP is delivered to the parent task.

Reported-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

They don't take signals individually, and even if they share signals with
the parent task, don't allow them to be delivered through the worker
thread. Linux does allow this kind of behavior for regular threads, but
it's really a compatability thing that we need not care about for the IO
threads.

Reported-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Pull misc fixes from Christian Brauner:

 - Jann reported sparse complaints because of a missing __user
   annotation in a helper we added way back when we added
   pidfd_send_signal() to avoid compat syscall handling. Fix it.

 - Yanfei replaces a reference in a comment to the _do_fork() helper I
   removed a while ago with a reference to the new kernel_clone()
   replacement

 - Alexander Guril added a simple coding style fix

* tag 'for-linus-2021-01-24' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  kthread: remove comments about old _do_fork() helper
  Kernel: fork.c: Fix coding style: Do not use {} around single-line statements
  signal: Add missing __user annotation to copy_siginfo_from_user_any

copy_siginfo_from_user_any() takes a userspace pointer as second
argument; annotate the parameter type accordingly.

Signed-off-by: Jann Horn <jannh@google.com>
Link: https://lore.kernel.org/r/20201207000252.138564-1-jannh@google.com
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

Song reported a boot regression in a kvm image with 5.11-rc, and bisected
it down to the below patch. Debugging this issue, turns out that the boot
stalled when a task is waiting on a pipe being released. As we no longer
run task_work from get_signal() unless it's queued with TWA_SIGNAL, the
task goes idle without running the task_work. This prevents ->release()
from being called on the pipe, which another boot task is waiting on.

For now, re-instate the unconditional task_work run from get_signal().
For 5.12, we'll collapse TWA_RESUME and TWA_SIGNAL, as it no longer
makes sense to have a distinction between the two. This will turn
task_work notification into a simple boolean, whether to notify or not.

Fixes: 98b89b649fce ("signal: kill JOBCTL_TASK_WORK")
Reported-by: Song Liu <songliubraving@fb.com>
Tested-by: John Stultz <john.stultz@linaro.org>
Tested-by: Douglas Anderson <dianders@chromium.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM/Clang version 11.0.1
Signed-off-by: Jens Axboe <axboe@kernel.dk>