[RFC 1/1] io_uring: lockdep annotate CQ locking

[Pavel Begunkov <asml.silence@gmail.com>]

Locking around CQE posting is complex and depends on options the ring is
created with, add more thorough lockdep annotations checking all
invariants.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/io_uring.c |  5 ++---
 io_uring/io_uring.h | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 6bed44855679..472574192dd6 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -731,6 +731,8 @@ static bool io_cqring_event_overflow(struct io_ring_ctx *ctx, u64 user_data,
 	size_t ocq_size = sizeof(struct io_overflow_cqe);
 	bool is_cqe32 = (ctx->flags & IORING_SETUP_CQE32);
 
+	lockdep_assert_held(&ctx->completion_lock);
+
 	if (is_cqe32)
 		ocq_size += sizeof(struct io_uring_cqe);
 
@@ -820,9 +822,6 @@ static bool io_fill_cqe_aux(struct io_ring_ctx *ctx, u64 user_data, s32 res,
 {
 	struct io_uring_cqe *cqe;
 
-	if (!ctx->task_complete)
-		lockdep_assert_held(&ctx->completion_lock);
-
 	ctx->cq_extra++;
 
 	/*
diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h
index e9f0d41ebb99..ab4b2a1c3b7e 100644
--- a/io_uring/io_uring.h
+++ b/io_uring/io_uring.h
@@ -79,6 +79,19 @@ bool __io_alloc_req_refill(struct io_ring_ctx *ctx);
 bool io_match_task_safe(struct io_kiocb *head, struct task_struct *task,
 			bool cancel_all);
 
+#define io_lockdep_assert_cq_locked(ctx)				\
+	do {								\
+		if (ctx->flags & IORING_SETUP_IOPOLL) {			\
+			lockdep_assert_held(&ctx->uring_lock);		\
+		} else if (!ctx->task_complete) {			\
+			lockdep_assert_held(&ctx->completion_lock);	\
+		} else if (ctx->submitter_task->flags & PF_EXITING) {	\
+			lockdep_assert(current_work());			\
+		} else {						\
+			lockdep_assert(current == ctx->submitter_task);	\
+		}							\
+	} while (0)
+
 static inline void io_req_task_work_add(struct io_kiocb *req)
 {
 	__io_req_task_work_add(req, true);
@@ -92,6 +105,8 @@ void io_cq_unlock_post(struct io_ring_ctx *ctx);
 static inline struct io_uring_cqe *io_get_cqe_overflow(struct io_ring_ctx *ctx,
 						       bool overflow)
 {
+	io_lockdep_assert_cq_locked(ctx);
+
 	if (likely(ctx->cqe_cached < ctx->cqe_sentinel)) {
 		struct io_uring_cqe *cqe = ctx->cqe_cached;
 
-- 
2.38.1