Hi Linus,
As mentioned last week, I'm sending the series on converting the io-wq
workers to be forked off the tasks in question instead of being kernel
threads that assume various bits of the original task identity. This is
on top of the for-5.12/io_uring branch I sent out yesterday, which I
think you've merged but just haven't pushed out yet.
This kills > 400 lines of code from io_uring/io-wq, and it's the worst
part of the code. We've had several bugs in this area, and the worry is
always that we could be missing some pieces for file types doing unusual
things (recent /dev/tty example comes to mind, userfaultfd reads
installing file descriptors is another fun one... - both of which need
special handling, and I bet it's not the last weird oddity we'll find).
With these identical workers, we can have full confidence that we're
never missing anything. That, in itself, is a huge win. Outside of that,
it's also more efficient since we're not wasting space and code on
tracking state, or switching between different states.
I'm sure we're going to find little things to patch up after this
series, but testing has been pretty thorough, from the usual regression
suite to production. Any issue that may crop up should be manageable.
There's also a nice series of further reductions we can do on top of
this, but I wanted to get the meat of it out sooner rather than later.
The general worry here isn't that it's fundamentally broken. Most of the
little issues we've found over the last week have been related to just
changes in how thread startup/exit is done, since that's the main
difference between using kthreads and these kinds of threads. In fact,
if all goes according to plan, I want to get this into the 5.10 and 5.11
stable branches as well.
That said, the changes outside of io_uring/io-wq are:
- arch setup, simple one-liner to each arch copy_thread()
implementation.
- Removal of net and proc restrictions for io_uring, they are no longer
needed or useful.
I'm leaving this to you if you're OK pulling it for this release, I'm
obviously in favor of doing so since I'm sending it to you. It'll help
me sleep better at night, and provide a *much* saner base for async
offload going forward. A bit of potential pain in the rc cycle is
totally worth it imho.
The following changes since commit b6c23dd5a483174f386e4c2e1711d9532e090c00:
io_uring: run task_work on io_uring_register() (2021-02-21 17:18:56 -0700)
are available in the Git repository at:
git://git.kernel.dk/linux-block.git tags/io_uring-worker.v3-2021-02-25
for you to fetch changes up to d6ce7f6761bf6d669d9c74ec5d3bd1bfe92380c5:
io-wq: remove now unused IO_WQ_BIT_ERROR (2021-02-25 10:19:43 -0700)
----------------------------------------------------------------
io_uring-worker.v3-2021-02-25
----------------------------------------------------------------
Jens Axboe (31):
Merge branch 'for-5.12/io_uring' into io_uring-worker.v3
io_uring: remove the need for relying on an io-wq fallback worker
io-wq: don't create any IO workers upfront
io_uring: disable io-wq attaching
io-wq: get rid of wq->use_refs
io_uring: tie async worker side to the task context
io-wq: don't pass 'wqe' needlessly around
arch: setup PF_IO_WORKER threads like PF_KTHREAD
kernel: treat PF_IO_WORKER like PF_KTHREAD for ptrace/signals
io-wq: fork worker threads from original task
io-wq: worker idling always returns false
io_uring: remove any grabbing of context
io_uring: remove io_identity
io-wq: only remove worker from free_list, if it was there
io-wq: make io_wq_fork_thread() available to other users
io_uring: move SQPOLL thread io-wq forked worker
Revert "proc: don't allow async path resolution of /proc/thread-self components"
Revert "proc: don't allow async path resolution of /proc/self components"
net: remove cmsg restriction from io_uring based send/recvmsg calls
io_uring: flag new native workers with IORING_FEAT_NATIVE_WORKERS
io-wq: remove nr_process accounting
io_uring: cleanup ->user usage
arch: ensure parisc/powerpc handle PF_IO_WORKER in copy_thread()
io_uring: ensure io-wq context is always destroyed for tasks
io-wq: fix races around manager/worker creation and task exit
io-wq: fix race around io_worker grabbing
io-wq: make buffered file write hashed work map per-ctx
io_uring: ensure SQPOLL startup is triggered before error shutdown
io-wq: improve manager/worker handling over exec
io_uring: fix SQPOLL thread handling over exec
io-wq: remove now unused IO_WQ_BIT_ERROR
arch/alpha/kernel/process.c | 2 +-
arch/arc/kernel/process.c | 2 +-
arch/arm/kernel/process.c | 2 +-
arch/arm64/kernel/process.c | 2 +-
arch/csky/kernel/process.c | 2 +-
arch/h8300/kernel/process.c | 2 +-
arch/hexagon/kernel/process.c | 2 +-
arch/ia64/kernel/process.c | 2 +-
arch/m68k/kernel/process.c | 2 +-
arch/microblaze/kernel/process.c | 2 +-
arch/mips/kernel/process.c | 2 +-
arch/nds32/kernel/process.c | 2 +-
arch/nios2/kernel/process.c | 2 +-
arch/openrisc/kernel/process.c | 2 +-
arch/parisc/kernel/process.c | 2 +-
arch/powerpc/kernel/process.c | 2 +-
arch/riscv/kernel/process.c | 2 +-
arch/s390/kernel/process.c | 2 +-
arch/sh/kernel/process_32.c | 2 +-
arch/sparc/kernel/process_32.c | 2 +-
arch/sparc/kernel/process_64.c | 2 +-
arch/um/kernel/process.c | 2 +-
arch/x86/kernel/process.c | 2 +-
arch/xtensa/kernel/process.c | 2 +-
fs/io-wq.c | 621 ++++++++---------
fs/io-wq.h | 35 +-
fs/io_uring.c | 1088 +++++++++++-------------------
fs/proc/self.c | 7 -
fs/proc/thread_self.c | 7 -
include/linux/io_uring.h | 22 +-
include/linux/net.h | 3 -
include/linux/sched.h | 3 +
include/uapi/linux/io_uring.h | 1 +
kernel/ptrace.c | 2 +-
kernel/signal.c | 4 +-
net/ipv4/af_inet.c | 1 -
net/ipv6/af_inet6.c | 1 -
net/socket.c | 10 -
38 files changed, 716 insertions(+), 1137 deletions(-)
--
Jens Axboe
