[PATCH 2/3] io_uring: Fix missing smp_mb() in io_cancel_async_work()
From: Muchun Song <hidden>
Date: 2020-09-15 08:23:07
Also in:
linux-fsdevel, lkml, stable
Subsystem:
filesystems (vfs and infrastructure), the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
The store to req->flags and load req->work_task should not be
reordering in io_cancel_async_work(). We should make sure that
either we store REQ_F_CANCE flag to req->flags or we see the
req->work_task setted in io_sq_wq_submit_work().
Fixes: 1c4404efcf2c ("io_uring: make sure async workqueue is canceled on exit")
Signed-off-by: Muchun Song <redacted>
---
fs/io_uring.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index de4f7b3a0d789..adaafe857b074 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c@@ -2252,6 +2252,12 @@ static void io_sq_wq_submit_work(struct work_struct *work) if (!ret) { req->work_task = current; + + /* + * Pairs with the smp_store_mb() (B) in + * io_cancel_async_work(). + */ + smp_mb(); /* A */ if (req->flags & REQ_F_CANCEL) { ret = -ECANCELED; goto end_req;
@@ -3719,7 +3725,15 @@ static void io_cancel_async_work(struct io_ring_ctx *ctx, req = list_first_entry(&ctx->task_list, struct io_kiocb, task_list); list_del_init(&req->task_list); - req->flags |= REQ_F_CANCEL; + + /* + * The below executes an smp_mb(), which matches with the + * smp_mb() (A) in io_sq_wq_submit_work() such that either + * we store REQ_F_CANCEL flag to req->flags or we see the + * req->work_task setted in io_sq_wq_submit_work(). + */ + smp_store_mb(req->flags, req->flags | REQ_F_CANCEL); /* B */ + if (req->work_task && (!files || req->files == files)) send_sig(SIGINT, req->work_task, 1); }
--
2.11.0