From: Vincent Fu <vincent.fu@wdc.com>
Date: Tue, 11 Sep 2018 13:01:56 +0000 (-0400)
Subject: rate_submit: synchronize accesses to io_u_queue->nr
X-Git-Tag: fio-3.10~2^2
X-Git-Url: https://git.kernel.dk/?p=fio.git;a=commitdiff_plain;h=b7aae4ba630b1dd6853f0794f00080f61b7cdc93

rate_submit: synchronize accesses to io_u_queue->nr

Accesses to io_u_queue->nr are not properly synchronized in offload
submission mode. put_io_u locks td but the parent td flags reflecting
the need to lock are not propogated to child threads when the child
threads are intialized.

The main thread accesses io_u_queue->nr via io_u_qpop() as it prepares
io_u's for handing off to the worker threads. The worker threads access
io_u_queue->nr via io_u_qpush() as they complete io_u's. When these
accesses are not protected by locks, io_u_qpop() will return NULL when
it means to provide a valid io_u pointer. This occurs in offload
submission mode with iodepth > 1.

Fixes: 26b3a18 ("Make td_io_u_lock/unlock() explicit")
---

diff --git a/rate-submit.c b/rate-submit.c
index 5c77a4e8..2f02fe2b 100644
--- a/rate-submit.c
+++ b/rate-submit.c
@@ -126,7 +126,7 @@ static int io_workqueue_init_worker_fn(struct submit_worker *sw)
 	clear_io_state(td, 1);
 
 	td_set_runstate(td, TD_RUNNING);
-	td->flags |= TD_F_CHILD;
+	td->flags |= TD_F_CHILD | TD_F_NEED_LOCK;
 	td->parent = parent;
 	return 0;