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| author | Jens Axboe <axboe@kernel.dk> | 2024-09-18 19:58:19 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2024-09-19 19:56:55 +0200 |
| commit | 04beb6e0e08c30c6f845f50afb7d7953603d7a6f (patch) | |
| tree | cbeada242f3abebae44b5db0d3d3890a888d7542 /io_uring | |
| parent | io_uring/sqpoll: do the napi busy poll outside the submission block (diff) | |
| download | linux-04beb6e0e08c30c6f845f50afb7d7953603d7a6f.tar.xz linux-04beb6e0e08c30c6f845f50afb7d7953603d7a6f.zip | |
io_uring: check for presence of task_work rather than TIF_NOTIFY_SIGNAL
If some part of the kernel adds task_work that needs executing, in terms
of signaling it'll generally use TWA_SIGNAL or TWA_RESUME. Those two
directly translate to TIF_NOTIFY_SIGNAL or TIF_NOTIFY_RESUME, and can
be used for a variety of use case outside of task_work.
However, io_cqring_wait_schedule() only tests explicitly for
TIF_NOTIFY_SIGNAL. This means it can miss if task_work got added for
the task, but used a different kind of signaling mechanism (or none at
all). Normally this doesn't matter as any task_work will be run once
the task exits to userspace, except if:
1) The ring is setup with DEFER_TASKRUN
2) The local work item may generate normal task_work
For condition 2, this can happen when closing a file and it's the final
put of that file, for example. This can cause stalls where a task is
waiting to make progress inside io_cqring_wait(), but there's nothing else
that will wake it up. Hence change the "should we schedule or loop around"
check to check for the presence of task_work explicitly, rather than just
TIF_NOTIFY_SIGNAL as the mechanism. While in there, also change the
ordering of what type of task_work first in terms of ordering, to both
make it consistent with other task_work runs in io_uring, but also to
better handle the case of defer task_work generating normal task_work,
like in the above example.
Reported-by: Jan Hendrik Farr <kernel@jfarr.cc>
Link: https://github.com/axboe/liburing/issues/1235
Cc: stable@vger.kernel.org
Fixes: 846072f16eed ("io_uring: mimimise io_cqring_wait_schedule")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'io_uring')
| -rw-r--r-- | io_uring/io_uring.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 1aca501efaf6..11c455b638a2 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2461,7 +2461,7 @@ static inline int io_cqring_wait_schedule(struct io_ring_ctx *ctx, return 1; if (unlikely(!llist_empty(&ctx->work_llist))) return 1; - if (unlikely(test_thread_flag(TIF_NOTIFY_SIGNAL))) + if (unlikely(task_work_pending(current))) return 1; if (unlikely(task_sigpending(current))) return -EINTR; @@ -2568,9 +2568,9 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events, u32 flags, * If we got woken because of task_work being processed, run it * now rather than let the caller do another wait loop. */ - io_run_task_work(); if (!llist_empty(&ctx->work_llist)) io_run_local_work(ctx, nr_wait); + io_run_task_work(); /* * Non-local task_work will be run on exit to userspace, but |