commit d094c4d5f5 ("tipc: add subscription refcount to avoid invalid
delete") accidently introduce the following deadlock scenarios:
CPU1: CPU2:
---------- ----------------
tipc_nametbl_publish
spin_lock_bh(&tn->nametbl_lock)
tipc_nametbl_insert_publ
tipc_nameseq_insert_publ
tipc_subscrp_report_overlap
tipc_subscrp_get
tipc_subscrp_send_event
tipc_close_conn
tipc_subscrb_release_cb
tipc_subscrb_delete
tipc_subscrp_put
tipc_subscrp_put
tipc_subscrp_kref_release
tipc_nametbl_unsubscribe
spin_lock_bh(&tn->nametbl_lock)
<<grab nametbl_lock again>>
CPU1: CPU2:
---------- ----------------
tipc_nametbl_stop
spin_lock_bh(&tn->nametbl_lock)
tipc_purge_publications
tipc_nameseq_remove_publ
tipc_subscrp_report_overlap
tipc_subscrp_get
tipc_subscrp_send_event
tipc_close_conn
tipc_subscrb_release_cb
tipc_subscrb_delete
tipc_subscrp_put
tipc_subscrp_put
tipc_subscrp_kref_release
tipc_nametbl_unsubscribe
spin_lock_bh(&tn->nametbl_lock)
<<grab nametbl_lock again>>
The root cause of two deadlocks is that we have to hold nametbl lock
when subscription is freed in tipc_subscrp_kref_release(). In order to
eliminate the need of taking nametbl lock in
tipc_subscrp_kref_release(), the functions protected by nametbl lock
in tipc_subscrp_kref_release() are moved to other places step by step
in the series.
Change log:
v2:
As Parth's comments, subscription is still present name table after
it's expired. To fix it, we introduce a workqueue, and when
subscription's timer is expired, the subscription will be pushed to
the workqueue through its work. When the work is scheduled, the
subscription be deleted finally.
Ying Xue (6):
tipc: advance the time of deleting subscription from
subscriber->subscrp_list
tipc: adjust the policy of holding subscription kref
tipc: adjust policy that sub->timer holds subscription kref
tipc: advance the time of calling tipc_nametbl_unsubscribe
tipc: remove unnecessary increasement of subscription refcount
tipc: delete expired subscription
net/tipc/name_table.c | 2 ++
net/tipc/server.h | 2 ++
net/tipc/subscr.c | 64 ++++++++++++++++++++++++++++++++++++---------------
net/tipc/subscr.h | 4 ++++
4 files changed, 54 insertions(+), 18 deletions(-)
--
2.7.4
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