[PATCH rdma-core v4 1/4] ibacm: Fix an incorrect expiration check for the retry timer

Michael J. Ruhl
2017-11-15T19:34:44Z

The acmp_process_wait_queue() checks to see if a message expiration
time has passed.

Because the check is for less than (<), if the timeout expires matches
the current time, the check will result in a timeout value of 0, and
the wait loop will spin until the next millisecond has passed.

Using example values to demonstrate the issue, we can see:

With '<':
wait = -2106577636 (no work)
wait = 2510 (message wait)
(process spins)
wait = 0 (expires - current time == 0)
wait = 0
wait = 0
... (1 ms of output)
wait = 0
wait = -2106580147 (retry complete)
wait = 2512

With '<=':
wait = -2106688780 (no work)
wait = 2512 ( message wait)
(process sleeps)
wait = -2106691293 (retry complete)
wait = 2512

Expire the message if the expires is less than or equal.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
---
ibacm/prov/acmp/src/acmp.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/ibacm/prov/acmp/src/acmp.c b/ibacm/prov/acmp/src/acmp.c
index 78d9a29..d707b8e 100644
--- a/ibacm/prov/acmp/src/acmp.c
+++ b/ibacm/prov/acmp/src/acmp.c
@@ -1507,7 +1507,7 @@ static void acmp_process_wait_queue(struct acmp_ep *ep, uint64_t *next_expire)
struct ibv_send_wr *bad_wr;

list_for_each_safe(&ep->wait_queue, msg, next, entry) {
- if (msg->expires < time_stamp_ms()) {
+ if (msg->expires <= time_stamp_ms()) {
list_del(&msg->entry);
(void) atomic_dec(&wait_cnt);
if (--msg->tries) {