Revert "io_uring: grab RCU read lock marking task run"

This reverts commit ed64f5c.

Since commit:

648790e ("io_uring: restore RCU read section in io_req_local_work_add()")

io_ctx_mark_taskrun() is only ever called with the RCU read lock
already held, like previously. Hence's there's no need for this commit
anymore, which grabbed the RCU read lock inside io_ctx_mark_taskrun().

Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: axboe

io_uring/tw.c

@@ -139,11 +139,11 @@ void tctx_task_work(struct callback_head *cb)
  */
 static void io_ctx_mark_taskrun(struct io_ring_ctx *ctx)
 {
+	lockdep_assert_in_rcu_read_lock();
+
 	if (ctx->flags & IORING_SETUP_TASKRUN_FLAG) {
-		struct io_rings *rings;
+		struct io_rings *rings = rcu_dereference(ctx->rings_rcu);
 
-		guard(rcu)();
-		rings = rcu_dereference(ctx->rings_rcu);
 		atomic_or(IORING_SQ_TASKRUN, &rings->sq_flags);
 	}
 }