On 3/16/24 03:54, Ming Lei wrote:
On Sat, Mar 16, 2024 at 02:54:19AM +0000, Pavel Begunkov wrote:
On 3/16/24 02:24, Ming Lei wrote:
On Sat, Mar 16, 2024 at 10:04 AM Ming Lei <ming.lei@xxxxxxxxxx> wrote:
On Fri, Mar 15, 2024 at 04:53:21PM -0600, Jens Axboe wrote:
On Fri, 15 Mar 2024 15:29:50 +0000, Pavel Begunkov wrote:
Patch 1 is a fix.
Patches 2-7 are cleanups mainly dealing with issue_flags conversions,
misundertsandings of the flags and of the tw state. It'd be great to have
even without even w/o the rest.
8-11 mandate ctx locking for task_work and finally removes the CQE
caches, instead we post directly into the CQ. Note that the cache is
used by multishot auxiliary completions.
[...]
Applied, thanks!
Hi Jens and Pavel,
Looks this patch causes hang when running './check ublk/002' in blktests.
Not take close look, and I guess it hangs in
io_uring_cmd_del_cancelable() -> io_ring_submit_lock
Thanks, the trace doesn't completely explains it, but my blind spot
was io_uring_cmd_done() potentially grabbing the mutex. They're
supposed to be irq safe mimicking io_req_task_work_add(), that's how
nvme passthrough uses it as well (but at least it doesn't need the
cancellation bits).
One option is to replace it with a spinlock, the other is to delay
the io_uring_cmd_del_cancelable() call to the task_work callback.
The latter would be cleaner and more preferable, but I'm lacking
context to tell if that would be correct. Ming, what do you think?
I prefer to the latter approach because the two cancelable helpers are
run in fast path.
Looks all new io_uring_cmd_complete() in ublk have this issue, and the
following patch should avoid them all.
The one I have in mind on top of the current tree would be like below.
Untested, and doesn't allow this cancellation thing for iopoll. I'll
prepare something tomorrow.
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index e45d4cd5ef82..000ba435451c 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -14,19 +14,15 @@
#include "rsrc.h"
#include "uring_cmd.h"
-static void io_uring_cmd_del_cancelable(struct io_uring_cmd *cmd,
- unsigned int issue_flags)
+static void io_uring_cmd_del_cancelable(struct io_uring_cmd *cmd)
{
struct io_kiocb *req = cmd_to_io_kiocb(cmd);
- struct io_ring_ctx *ctx = req->ctx;
if (!(cmd->flags & IORING_URING_CMD_CANCELABLE))
return;
cmd->flags &= ~IORING_URING_CMD_CANCELABLE;
- io_ring_submit_lock(ctx, issue_flags);
hlist_del(&req->hash_node);
- io_ring_submit_unlock(ctx, issue_flags);
}
/*
@@ -80,6 +76,15 @@ static inline void io_req_set_cqe32_extra(struct io_kiocb *req,
req->big_cqe.extra2 = extra2;
}
+static void io_req_task_cmd_complete(struct io_kiocb *req,
+ struct io_tw_state *ts)
+{
+ struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
+
+ io_uring_cmd_del_cancelable(ioucmd);
+ io_req_task_complete(req, ts);
+}
+
/*
* Called by consumers of io_uring_cmd, if they originally returned
* -EIOCBQUEUED upon receiving the command.
@@ -89,8 +94,6 @@ void io_uring_cmd_done(struct io_uring_cmd *ioucmd, ssize_t ret, ssize_t res2,
{
struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
- io_uring_cmd_del_cancelable(ioucmd, issue_flags);
-
if (ret < 0)
req_set_fail(req);
@@ -105,7 +108,7 @@ void io_uring_cmd_done(struct io_uring_cmd *ioucmd, ssize_t ret, ssize_t res2,
return;
io_req_complete_defer(req);
} else {
- req->io_task_work.func = io_req_task_complete;
+ req->io_task_work.func = io_req_task_cmd_complete;
io_req_task_work_add(req);
}
}
--
Pavel Begunkov
