bnxt_re/lib: Avoid applications hang in resize cq operation

[ Upstream commit ec106a3 ]

Library currently waits indefinitely for the resize CQ
completion notification from the hardware. Due to hardware
failure in handling the operation, there is a possible
application hang.

Add a loop count with a busy wait of definite time to avoid
the application hang.

Fixes: ae8b278 ("bnxt_re/lib: Resize CQ support")
Signed-off-by: Chandramohan Akula <chandramohan.akula@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Nicolas Morey <nmorey@suse.com>

providers/bnxt_re/main.h

@@ -61,6 +61,7 @@
 #define CHIP_NUM_57508		0x1750
 #define CHIP_NUM_57504		0x1751
 #define CHIP_NUM_57502		0x1752
+#define BNXT_NSEC_PER_SEC  1000000000UL
 
 struct bnxt_re_chip_ctx {
 	__u16 chip_num;
@@ -531,4 +532,39 @@ static inline void bnxt_re_copy_data_to_pb(struct bnxt_re_push_buffer *pbuf,
 		mmio_write64(dst, *src);
 	}
 }
+
+static void timespec_sub(const struct timespec *a, const struct timespec *b,
+            struct timespec *res)
+{
+   res->tv_sec = a->tv_sec - b->tv_sec;
+   res->tv_nsec = a->tv_nsec - b->tv_nsec;
+   if (res->tv_nsec < 0) {
+       res->tv_sec--;
+       res->tv_nsec += BNXT_NSEC_PER_SEC;
+   }
+}
+
+/*
+ * Function waits in a busy loop for a given nano seconds
+ * The maximum wait period allowed is less than one second
+ */
+static inline void bnxt_re_sub_sec_busy_wait(uint32_t nsec)
+{
+   struct timespec start, cur, res;
+
+   if (nsec >= BNXT_NSEC_PER_SEC)
+       return;
+
+   if (clock_gettime(CLOCK_REALTIME, &start))
+       return;
+
+   while (1) {
+       if (clock_gettime(CLOCK_REALTIME, &cur))
+           return;
+       timespec_sub(&cur, &start, &res);
+       if (res.tv_nsec >= nsec)
+           break;
+   }
+}
+
 #endif

providers/bnxt_re/verbs.c

@@ -315,6 +315,8 @@ int bnxt_re_resize_cq(struct ibv_cq *ibvcq, int ncqe)
 	struct bnxt_re_cq *cq = to_bnxt_re_cq(ibvcq);
 	struct ib_uverbs_resize_cq_resp resp = {};
 	struct ubnxt_re_resize_cq cmd = {};
+	uint16_t msec_wait = 100;
+	uint16_t exit_cnt = 20;
 	int rc = 0;
 
 	if (ncqe > dev->max_cq_depth)
@@ -355,6 +357,13 @@ int bnxt_re_resize_cq(struct ibv_cq *ibvcq, int ncqe)
 			list_add_tail(&cq->prev_cq_head, &compl->list);
 			compl = NULL;
 			memset(&tmp_wc, 0, sizeof(tmp_wc));
+		} else {
+			exit_cnt--;
+			if (unlikely(!exit_cnt)) {
+				rc = -EIO;
+				break;
+			}
+			bnxt_re_sub_sec_busy_wait(msec_wait * 1000000);
 		}
 	}
 done: