net/smc: Fix hung_task when removing SMC-R devices

A hung_task is observed when removing SMC-R devices. Suppose that
a link group has two active links(lnk_A, lnk_B) associated with two
different SMC-R devices(dev_A, dev_B). When dev_A is removed, the
link group will be removed from smc_lgr_list and added into
lgr_linkdown_list. lnk_A will be cleared and smcibdev(A)->lnk_cnt
will reach to zero. However, when dev_B is removed then, the link
group can't be found in smc_lgr_list and lnk_B won't be cleared,
making smcibdev->lnk_cnt never reaches zero, which causes a hung_task.

This patch fixes this issue by restoring the implementation of
smc_smcr_terminate_all() to what it was before commit 349d43127dac
("net/smc: fix kernel panic caused by race of smc_sock"). The original
implementation also satisfies the intention that make sure QP destroy
earlier than CQ destroy because we will always wait for smcibdev->lnk_cnt
reaches zero, which guarantees QP has been destroyed.

Fixes: 349d43127dac ("net/smc: fix kernel panic caused by race of smc_sock")
Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 7199eee..29525d0 100644 (file)
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -1531,16 +1531,11 @@ void smc_smcd_terminate_all(struct smcd_dev *smcd)
 /* Called when an SMCR device is removed or the smc module is unloaded.
  * If smcibdev is given, all SMCR link groups using this device are terminated.
  * If smcibdev is NULL, all SMCR link groups are terminated.
- *
- * We must wait here for QPs been destroyed before we destroy the CQs,
- * or we won't received any CQEs and cdc_pend_tx_wr cannot reach 0 thus
- * smc_sock cannot be released.
  */
 void smc_smcr_terminate_all(struct smc_ib_device *smcibdev)
 {
        struct smc_link_group *lgr, *lg;
        LIST_HEAD(lgr_free_list);
-       LIST_HEAD(lgr_linkdown_list);
        int i;
 
        spin_lock_bh(&smc_lgr_list.lock);
@@ -1552,7 +1547,7 @@ void smc_smcr_terminate_all(struct smc_ib_device *smcibdev)
                list_for_each_entry_safe(lgr, lg, &smc_lgr_list.list, list) {
                        for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
                                if (lgr->lnk[i].smcibdev == smcibdev)
-                                       list_move_tail(&lgr->list, &lgr_linkdown_list);
+                                       smcr_link_down_cond_sched(&lgr->lnk[i]);
                        }
                }
        }
@@ -1564,16 +1559,6 @@ void smc_smcr_terminate_all(struct smc_ib_device *smcibdev)
                __smc_lgr_terminate(lgr, false);
        }
 
-       list_for_each_entry_safe(lgr, lg, &lgr_linkdown_list, list) {
-               for (i = 0; i < SMC_LINKS_PER_LGR_MAX; i++) {
-                       if (lgr->lnk[i].smcibdev == smcibdev) {
-                               mutex_lock(&lgr->llc_conf_mutex);
-                               smcr_link_down_cond(&lgr->lnk[i]);
-                               mutex_unlock(&lgr->llc_conf_mutex);
-                       }
-               }
-       }
-
        if (smcibdev) {
                if (atomic_read(&smcibdev->lnk_cnt))
                        wait_event(smcibdev->lnks_deleted,