[PATCH 11/19] libfc: Reduce exchange lock contention in fc_exch_recv_abts()

Robert Love
2013-10-21T18:01:29Z

Reduce the time during which the exchange lock is held by allocating
a frame before obtaining the exchange lock.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Cc: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
---
drivers/scsi/libfc/fc_exch.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/libfc/fc_exch.c b/drivers/scsi/libfc/fc_exch.c
index 2a7fd5a..47ebc7b 100644
--- a/drivers/scsi/libfc/fc_exch.c
+++ b/drivers/scsi/libfc/fc_exch.c
@@ -1307,9 +1307,16 @@ static void fc_exch_recv_abts(struct fc_exch *ep, struct fc_frame *rx_fp)

if (!ep)
goto reject;
+
+ fp = fc_frame_alloc(ep->lp, sizeof(*ap));
+ if (!fp)
+ goto free;
+
spin_lock_bh(&ep->ex_lock);
if (ep->esb_stat & ESB_ST_COMPLETE) {
spin_unlock_bh(&ep->ex_lock);
+
+ fc_frame_free(fp);
goto reject;
}
if (!(ep->esb_stat & ESB_ST_REC_QUAL)) {
@@ -1317,12 +1324,6 @@ static void fc_exch_recv_abts(struct fc_exch *ep, struct fc_frame *rx_fp)
fc_exch_hold(ep); /* hold for REC_QUAL */
}
fc_exch_timer_set_locked(ep, ep->r_a_tov);
-
- fp = fc_frame_alloc(ep->lp, sizeof(*ap));
- if (!fp) {
- spin_unlock_bh(&ep->ex_lock);
- goto free;
- }
fh = fc_frame_header_get(fp);
ap = fc_frame_payload_get(fp, sizeof(*ap));
memset(ap, 0, sizeof(*ap));
@@ -1338,13 +1339,14 @@ static void fc_exch_recv_abts(struct fc_exch *ep, struct fc_frame *rx_fp)
fc_seq_send_last(sp, fp, FC_RCTL_BA_ACC, FC_TYPE_BLS);
ep->esb_stat |= ESB_ST_ABNORMAL;
spin_unlock_bh(&ep->ex_lock);
+
+free:
fc_frame_free(rx_fp);
return;

reject:
fc_exch_send_ba_rjt(rx_fp, FC_BA_RJT_UNABLE, FC_BA_RJT_INV_XID);
-free:
- fc_frame_free(rx_fp);
+ goto free;
}

/**