io_uring: remove the need for relying on an io-wq fallback worker
We hit this case when the task is exiting, and we need somewhere to
do background cleanup of requests. Instead of relying on the io-wq
task manager to do this work for us, just stuff it somewhere where
we can safely run it ourselves directly.
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/fs/io_uring.c b/fs/io_uring.c
index ace7494..e3eb373 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -456,6 +456,9 @@ struct io_ring_ctx {
struct io_restriction restrictions;
+ /* exit task_work */
+ struct callback_head *exit_task_work;
+
/* Keep this last, we don't need it for the fast path */
struct work_struct exit_work;
};
@@ -2328,11 +2331,14 @@ static int io_req_task_work_add(struct io_kiocb *req)
static void io_req_task_work_add_fallback(struct io_kiocb *req,
task_work_func_t cb)
{
- struct task_struct *tsk = io_wq_get_task(req->ctx->io_wq);
+ struct io_ring_ctx *ctx = req->ctx;
+ struct callback_head *head;
init_task_work(&req->task_work, cb);
- task_work_add(tsk, &req->task_work, TWA_NONE);
- wake_up_process(tsk);
+ do {
+ head = READ_ONCE(ctx->exit_task_work);
+ req->task_work.next = head;
+ } while (cmpxchg(&ctx->exit_task_work, head, &req->task_work) != head);
}
static void __io_req_task_cancel(struct io_kiocb *req, int error)
@@ -8835,6 +8841,28 @@ static int io_remove_personalities(int id, void *p, void *data)
return 0;
}
+static void io_run_ctx_fallback(struct io_ring_ctx *ctx)
+{
+ struct callback_head *work, *head, *next;
+
+ do {
+ do {
+ head = NULL;
+ work = READ_ONCE(ctx->exit_task_work);
+ } while (cmpxchg(&ctx->exit_task_work, work, head) != work);
+
+ if (!work)
+ break;
+
+ do {
+ next = work->next;
+ work->func(work);
+ work = next;
+ cond_resched();
+ } while (work);
+ } while (1);
+}
+
static void io_ring_exit_work(struct work_struct *work)
{
struct io_ring_ctx *ctx = container_of(work, struct io_ring_ctx,
@@ -8848,6 +8876,7 @@ static void io_ring_exit_work(struct work_struct *work)
*/
do {
io_uring_try_cancel_requests(ctx, NULL, NULL);
+ io_run_ctx_fallback(ctx);
} while (!wait_for_completion_timeout(&ctx->ref_comp, HZ/20));
io_ring_ctx_free(ctx);
}
@@ -9243,6 +9272,8 @@ static int io_uring_flush(struct file *file, void *data)
io_req_caches_free(ctx, current);
}
+ io_run_ctx_fallback(ctx);
+
if (!tctx)
return 0;