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io_uring/futex: only mark private futex waits as inflight

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Inflight tracking of futex wait requests exists to ensure that do_exit()
-> io_uring_files_cancel() cancels them before the mm goes away, as a
private futex wait depends on the mm private futex hash staying alive
for the duration of the request.

Shared futexes have no such dependency. A FLAGS_SHARED request always
resolves to either an inode based key or an mm-shared key, both of which
fail futex_key_is_private() and hence always hash into the global futex
hash, whose lifetime isn't tied to the mm.

Only mark vectored futex waits as inflight if the futex is private.

Cc: stable@vger.kernel.org
Fixes: 079afb081c ("io_uring/futex: mark wait requests as inflight")
Link: https://lore.kernel.org/io-uring/CANGjgdn=R_qyUdE=j9za+vkmqcxacbP-84OHXF4nZ4ho9qRyVg@mail.gmail.com/
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe
2026-07-30 10:35:28 -06:00
parent 73e7019097
commit 4d327bbd1c
1 changed files with 13 additions and 4 deletions
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io_uring/futex.c
+13 -4
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@@ -154,14 +154,16 @@ int io_futex_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
int io_futex_wait_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
int ret;
ret = io_futex_prep(req, sqe);
if (unlikely(ret))
return ret;
/* Mark as inflight, so file exit cancelation will find it */
io_req_track_inflight(req);
/* inflight tracking only needed for mm private hash */
if (!(iof->futex_flags & FLAGS_SHARED))
io_req_track_inflight(req);
return 0;
}
@@ -186,6 +188,7 @@ int io_futexv_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
{
struct io_futex *iof = io_kiocb_to_cmd(req, struct io_futex);
struct io_futexv_data *ifd;
unsigned int i;
int ret;
/* No flags or mask supported for waitv */
@@ -210,8 +213,14 @@ int io_futexv_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
return ret;
}
/* Mark as inflight, so file exit cancelation will find it */
io_req_track_inflight(req);
/* inflight tracking only needed for mm private hash */
for (i = 0; i < iof->futex_nr; i++) {
if (!(ifd->futexv[i].w.flags & FLAGS_SHARED)) {
io_req_track_inflight(req);
break;
}
}
iof->futexv_unqueued = 0;
req->flags |= REQ_F_ASYNC_DATA;
req->async_data = ifd;