From: Vincent Fu <vincent.fu@xxxxxxx>
Add some comments to clarify how locking is used for cross-job overlap
checking
---
backend.c | 5 +++++
ioengines.c | 7 +++++++
rate-submit.c | 8 ++++++++
3 files changed, 20 insertions(+)
diff --git a/backend.c b/backend.c
index cc3c4e78..2a05abb7 100644
--- a/backend.c
+++ b/backend.c
@@ -1874,6 +1874,11 @@ static void *thread_main(void *data)
"perhaps try --debug=io option for details?\n",
td->o.name, td->io_ops->name);
+ /*
+ * Acquire this lock if we were doing overlap checking in
+ * offload mode so that we don't clean up this job while
+ * another thread is checking its io_u's for overlap
+ */
if (td->o.serialize_overlap && td->o.io_submit_mode == IO_MODE_OFFLOAD)
pthread_mutex_lock(&overlap_check);
td_set_runstate(td, TD_FINISHING);
diff --git a/ioengines.c b/ioengines.c
index 47f606a7..fca1f0ed 100644
--- a/ioengines.c
+++ b/ioengines.c
@@ -288,6 +288,13 @@ enum fio_q_status td_io_queue(struct thread_data *td, struct io_u *io_u)
assert((io_u->flags & IO_U_F_FLIGHT) == 0);
io_u_set(td, io_u, IO_U_F_FLIGHT);
+
+ /*
+ * If overlap checking was enabled in offload mode we
+ * can release this lock that was acquired when we
+ * started the overlap check because the IO_U_F_FLIGHT
+ * flag is now set
+ */
if (td->o.serialize_overlap && td->o.io_submit_mode == IO_MODE_OFFLOAD)
pthread_mutex_unlock(&overlap_check);
diff --git a/rate-submit.c b/rate-submit.c
index 68ad755d..e5c62043 100644
--- a/rate-submit.c
+++ b/rate-submit.c
@@ -21,6 +21,14 @@ static void check_overlap(struct io_u *io_u)
* time to prevent two threads from thinking the coast
* is clear and then submitting IOs that overlap with
* each other
+ *
+ * If an overlap is found, release the lock and
+ * re-acquire it before checking again to give other
+ * threads a chance to make progress
+ *
+ * If an overlap is not found, release the lock when the
+ * io_u's IO_U_F_FLIGHT flag is set so that this io_u
+ * can be checked by other threads as they assess overlap
*/
pthread_mutex_lock(&overlap_check);
for_each_td(td, i) {
--
2.17.1
