Commit 56d99e81 authored by Wen Gu's avatar Wen Gu Committed by David S. Miller
Browse files

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 349d4312
("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: 349d4312 ("net/smc: fix kernel panic caused by race of smc_sock")
Signed-off-by: default avatarWen Gu <guwen@linux.alibaba.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0a6e6b3c

net/smc/smc_core.c

+1 −16
Original line number Diff line number Diff line
@@ -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,