We have two checks of task->flags & PF_EXITING left:
1) In io_req_task_submit(), which is called in task_work and hence always
in the context of the original task. That means that
req->task == current, and hence checking ->flags is totally fine.
2) In io_poll_rewait(), where we need to stop re-arming poll to prevent
it interfering with cancelation. This is only run from task_work as
well, and hence for this case too req->task == current.
Add a comment to both spots detailing that.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Move earlier the check for whether __io_queue_proc() tries to poll
already polled waitqueue, and do the same for the second poll entry, if
any. Shouldn't really matter, but at least it would have a more
predictable behaviour.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/8cb428cfe8ade0fd055859fabb878db8777d4c2f.1629228203.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We have io_req_complete_post() to post a CQE and put the request. It
takes care of all synchronisation and is more concise and efficent, so
replace all hancoded occurrences of
"lock; post CQE; unlock; + put_req()" with io_req_complete_post().
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/2c83463458a613f9d870e5147eb134da2aa70779.1629228203.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linked timeout handling during issuing is heavy, it adds extra
instructions and forces to save the next linked timeout before
io_issue_sqe().
Follwing the same reasoning as in refcounting patches, a request can't
be freed by the time it returns from io_issue_sqe(), so now we don't
need to do io_prep_linked_timeout() in advance, and it can be delayed to
colder paths optimising the generic path.
Also, it should also save quite a lot for requests with linked timeouts
and completed inline on timeout spinlocking + hrtimer_start() +
hrtimer_try_to_cancel() and so on.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/19bfc9a0d26c5c5f1e359f7650afe807ca8ef879.1628981736.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Tracking linked timeouts as infligh was needed to make sure that io-wq
is not destroyed by io_uring_cancel_generic() racing with
io_async_cancel_one() accessing it. Now, cancellations issued by linked
timeouts are done in the task context, so it's already synchronised.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/e1b05cf47cb69df2305efdbee8cf7ba36f46c1a3.1628981736.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
io_req_free_batch() has a __must_hold annotation referencing a
request being passed in, but we're passing in the context.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We can merge two spin_unlock() operations to one since we removed some
code not long ago.
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
When doing cancellation, we use a parameter to indicate where it's from
do_exit or exec. So a boolean value is good enough for this, remove the
struct files* as it is not necessary.
Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
[axboe: fixup io_uring_files_cancel for !CONFIG_IO_URING]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
As submission references are gone, there is only one initial reference
left. Instead of actually doing atomic refcounting, add a flag
indicating whether we're going to take more refs or doing any other sync
magic. The flag should be set before the request may get used in
parallel.
Together with the previous patch it saves 2 refcount atomics per request
for IOPOLL and IRQ completions, and 1 atomic per req for inline
completions, with some exceptions. In particular, currently, there are
three cases, when the refcounting have to be enabled:
- Polling, including apoll. Because double poll entries takes a ref.
Might get relaxed in the near future.
- Link timeouts, enabled for both, the timeout and the request it's
bound to, because they work in-parallel and we need to synchronise
to cancel one of them on completion.
- When a request gets in io-wq, because it doesn't hold uring_lock and
we need guarantees of submission references.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/8b204b6c5f6643062270a1913d6d3a7f8f795fd9.1628705069.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Requests are by default given with two references, submission and
completion. Completion references are straightforward, they represent
request ownership and are put when a request is completed or so.
Submission references are a bit more trickier. They're needed when
io_issue_sqe() followed deep into the submission stack (e.g. in fs,
block, drivers, etc.), request may have given away for concurrent
execution or already completed, and the code unwinding back to
io_issue_sqe() may be accessing some pieces of our requests, e.g.
file or iov.
Now, we prevent such async/in-depth completions by pushing requests
through task_work. Punting to io-wq is also done through task_works,
apart from a couple of cases with a pretty well known context. So,
there're two cases:
1) io_issue_sqe() from the task context and protected by ->uring_lock.
Either requests return back to io_uring or handed to task_work, which
won't be executed because we're currently controlling that task. So,
we can be sure that requests are staying alive all the time and we don't
need submission references to pin them.
2) io_issue_sqe() from io-wq, which doesn't hold the mutex. The role of
submission reference is played by io-wq reference, which is put by
io_wq_submit_work(). Hence, it should be fine.
Considering that, we can carefully kill the submission reference.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/6b68f1c763229a590f2a27148aee77767a8d7750.1628705069.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We have no hard/soft IRQ users of this lock left, remove any IRQ
disabling/saving and restoring when grabbing this lock.
This is straight forward with no users entering with IRQs disabled
anymore, the only thing to look out for is the waitqueue poll head
lock which nests inside the completion lock. That needs IRQs disabled,
and hence we have to do that now instead of relying on the outer lock
doing so.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This is in preparation to making the completion lock work outside of
hard/soft IRQ context.
Add a timeout_lock to handle the ordering of timeout completions or
cancelations with the timeouts actually triggering.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
For requests with non-fixed files, instead of grabbing just one
reference, we get by the number of left requests, so the following
requests using the same file can take it without atomics.
However, it's not all win. If there is one request in the middle
not using files or having a fixed file, we'll need to put back the left
references. Even worse if an application submits requests dealing with
different files, it will do a put for each new request, so doubling the
number of atomics needed. Also, even if not used, it's still takes some
cycles in the submission path.
If a file used many times, it rather makes sense to pre-register it, if
not, we may fall in the described pitfall. So, this optimisation is a
matter of use case. Go with the simpliest code-wise way, remove it.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
After recent fixes, tctx_task_work() always does proper spinlocking
before looking into ->task_list, so now we don't need atomics for
->task_state, replace it with non-atomic task_running using the critical
section.
Tide it up, combine two separate block with spinlocking, and always try
to splice in there, so we do less locking when new requests are arriving
during the function execution.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
[axboe: fix missing ->task_running reset on task_work_add() failure]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We cache all the reference to task + tctx, so if io_put_task() is
called by the corresponding task itself, we can save on atomics and
return the refs right back into the cache.
It's beneficial for all inline completions, and also iopolling, when
polling and submissions are done by the same task, including
SQPOLL|IOPOLL.
Note: io_uring_cancel_generic() can return refs to the cache as well,
so those should be flushed in the loop for tctx_inflight() to work
right.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/6fe9646b3cb70e46aca1f58426776e368c8926b3.1628471125.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
If io_ring_exit_work() can't get it done in 5 minutes, something is
going very wrong, don't keep spinning at HZ / 20 rate, it doesn't help
and it may take much of CPU time if there is a lot of workers stuck as
such.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/9e2d1ca81d569f6bc628af1a42ff6663bff7ce9c.1628471125.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Turns out we always init struct io_wait_queue in io_cqring_wait(), even
if it's not used after, i.e. there are already enough of CQEs. And often
it's exactly what happens, for instance, requests may have been
completed inline, or in case of io_uring_enter(submit=N, wait=1).
It shows up in my profiler, so optimise it by delaying the struct init.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/6f1b81c60b947d165583dc333947869c3d85d037.1628471125.git.asml.silence@gmail.com
[axboe: fixed up for new cqring wait]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
IOPOLL users should care more about getting completions for requests
they submitted, but not in "device did/completed something". Currently,
io_do_iopoll() may return a positive number, which will instruct
io_iopoll_check() to break the loop and end the syscall, even if there
is not enough CQEs or none at all.
Don't return positive numbers, so io_iopoll_check() exits only when it
gets an actual error, need reschedule or got enough CQEs.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/641a88f751623b6758303b3171f0a4141f06726e.1628471125.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
We prefer nornal task_works even if it would fail requests inside. Kill
a PF_EXITING check in io_req_task_work_add(), task_work_add() handles
well dying tasks, i.e. return error when can't enqueue due to late
stages of do_exit().
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/fc14297e8441cd8f5d1743a2488cf0df09bf48ac.1628471125.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
