On 3/29/24 13:31, Jens Axboe wrote:
On 3/29/24 6:51 AM, Pavel Begunkov wrote:
On 3/28/24 18:52, Jens Axboe wrote:
All our task_work handling is targeted at the state in the io_kiocb
itself, which is what it is being used for. However, MSG_RING rolls its
own task_work handling, ignoring how that is usually done.
In preparation for switching MSG_RING to be able to use the normal
task_work handling, add io_req_task_work_add_remote() which allows the
caller to pass in the target io_ring_ctx and task.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
io_uring/io_uring.c | 27 +++++++++++++++++++--------
io_uring/io_uring.h | 2 ++
2 files changed, 21 insertions(+), 8 deletions(-)
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 9978dbe00027..609ff9ea5930 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -1241,9 +1241,10 @@ void tctx_task_work(struct callback_head *cb)
WARN_ON_ONCE(ret);
}
-static inline void io_req_local_work_add(struct io_kiocb *req, unsigned tw_flags)
+static inline void io_req_local_work_add(struct io_kiocb *req,
+ struct io_ring_ctx *ctx,
+ unsigned tw_flags)
{
- struct io_ring_ctx *ctx = req->ctx;
unsigned nr_wait, nr_tw, nr_tw_prev;
unsigned long flags;
@@ -1291,9 +1292,10 @@ static inline void io_req_local_work_add(struct io_kiocb *req, unsigned tw_flags
wake_up_state(ctx->submitter_task, TASK_INTERRUPTIBLE);
}
-static void io_req_normal_work_add(struct io_kiocb *req)
+static void io_req_normal_work_add(struct io_kiocb *req,
+ struct task_struct *task)
{
- struct io_uring_task *tctx = req->task->io_uring;
+ struct io_uring_task *tctx = task->io_uring;
struct io_ring_ctx *ctx = req->ctx;
unsigned long flags;
bool was_empty;
@@ -1319,7 +1321,7 @@ static void io_req_normal_work_add(struct io_kiocb *req)
return;
}
- if (likely(!task_work_add(req->task, &tctx->task_work, ctx->notify_method)))
+ if (likely(!task_work_add(task, &tctx->task_work, ctx->notify_method)))
return;
io_fallback_tw(tctx, false);
@@ -1328,9 +1330,18 @@ static void io_req_normal_work_add(struct io_kiocb *req)
void __io_req_task_work_add(struct io_kiocb *req, unsigned flags)
{
if (req->ctx->flags & IORING_SETUP_DEFER_TASKRUN)
- io_req_local_work_add(req, flags);
+ io_req_local_work_add(req, req->ctx, flags);
+ else
+ io_req_normal_work_add(req, req->task);
+}
+
+void io_req_task_work_add_remote(struct io_kiocb *req, struct task_struct *task,
+ struct io_ring_ctx *ctx, unsigned flags)
Urgh, even the declration screams that there is something wrong
considering it _either_ targets @ctx or @task.
Just pass @ctx, so it either use ctx->submitter_task or
req->task, hmm?
I actually since changed the above to use a common helper, so was
scratching my head a bit over your comment as it can't really work in
that setup without needing to check for whether ->submitter_task is set
or not. But I do agree this would be nicer, so I'll just return to using
the separate helpers for this and it should fall out nicely. The only
odd caller is the MSG_RING side, so makes sense to have it a bit more
separate rather than try and fold it in with the regular side of using
task_work.
A side note, it's a dangerous game, I told it before. At least
it would've been nice to abuse lockdep in a form of:
io_req_task_complete(req, tw, ctx) {
lockdep_assert(req->ctx == ctx);
...
}
but we don't have @ctx there, maybe we'll add it to tw later.
Agree, but a separate thing imho.
It's not in a sense that condition couldn't have happened
before and the patch opening all possibilities.
We actually have @ctx via struct io_tctx_node, so considering
fallback it would probably be:
lockdep_assert(!current->io_uring ||
current->io_uring->ctx == req->ctx);
--
Pavel Begunkov
