This is a note to let you know that I've just added the patch titled
net/smc: fix deadlock triggered by cancel_delayed_work_syn()
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-smc-fix-deadlock-triggered-by-cancel_delayed_wor.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 302552c7cceb5c40da15c2b73237e947ae5d061b
Author: Wenjia Zhang <wenjia@xxxxxxxxxxxxx>
Date: Mon Mar 13 11:08:28 2023 +0100
net/smc: fix deadlock triggered by cancel_delayed_work_syn()
[ Upstream commit 13085e1b5cab8ad802904d72e6a6dae85ae0cd20 ]
The following LOCKDEP was detected:
Workqueue: events smc_lgr_free_work [smc]
WARNING: possible circular locking dependency detected
6.1.0-20221027.rc2.git8.56bc5b569087.300.fc36.s390x+debug #1 Not tainted
------------------------------------------------------
kworker/3:0/176251 is trying to acquire lock:
00000000f1467148 ((wq_completion)smc_tx_wq-00000000#2){+.+.}-{0:0},
at: __flush_workqueue+0x7a/0x4f0
but task is already holding lock:
0000037fffe97dc8 ((work_completion)(&(&lgr->free_work)->work)){+.+.}-{0:0},
at: process_one_work+0x232/0x730
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #4 ((work_completion)(&(&lgr->free_work)->work)){+.+.}-{0:0}:
__lock_acquire+0x58e/0xbd8
lock_acquire.part.0+0xe2/0x248
lock_acquire+0xac/0x1c8
__flush_work+0x76/0xf0
__cancel_work_timer+0x170/0x220
__smc_lgr_terminate.part.0+0x34/0x1c0 [smc]
smc_connect_rdma+0x15e/0x418 [smc]
__smc_connect+0x234/0x480 [smc]
smc_connect+0x1d6/0x230 [smc]
__sys_connect+0x90/0xc0
__do_sys_socketcall+0x186/0x370
__do_syscall+0x1da/0x208
system_call+0x82/0xb0
-> #3 (smc_client_lgr_pending){+.+.}-{3:3}:
__lock_acquire+0x58e/0xbd8
lock_acquire.part.0+0xe2/0x248
lock_acquire+0xac/0x1c8
__mutex_lock+0x96/0x8e8
mutex_lock_nested+0x32/0x40
smc_connect_rdma+0xa4/0x418 [smc]
__smc_connect+0x234/0x480 [smc]
smc_connect+0x1d6/0x230 [smc]
__sys_connect+0x90/0xc0
__do_sys_socketcall+0x186/0x370
__do_syscall+0x1da/0x208
system_call+0x82/0xb0
-> #2 (sk_lock-AF_SMC){+.+.}-{0:0}:
__lock_acquire+0x58e/0xbd8
lock_acquire.part.0+0xe2/0x248
lock_acquire+0xac/0x1c8
lock_sock_nested+0x46/0xa8
smc_tx_work+0x34/0x50 [smc]
process_one_work+0x30c/0x730
worker_thread+0x62/0x420
kthread+0x138/0x150
__ret_from_fork+0x3c/0x58
ret_from_fork+0xa/0x40
-> #1 ((work_completion)(&(&smc->conn.tx_work)->work)){+.+.}-{0:0}:
__lock_acquire+0x58e/0xbd8
lock_acquire.part.0+0xe2/0x248
lock_acquire+0xac/0x1c8
process_one_work+0x2bc/0x730
worker_thread+0x62/0x420
kthread+0x138/0x150
__ret_from_fork+0x3c/0x58
ret_from_fork+0xa/0x40
-> #0 ((wq_completion)smc_tx_wq-00000000#2){+.+.}-{0:0}:
check_prev_add+0xd8/0xe88
validate_chain+0x70c/0xb20
__lock_acquire+0x58e/0xbd8
lock_acquire.part.0+0xe2/0x248
lock_acquire+0xac/0x1c8
__flush_workqueue+0xaa/0x4f0
drain_workqueue+0xaa/0x158
destroy_workqueue+0x44/0x2d8
smc_lgr_free+0x9e/0xf8 [smc]
process_one_work+0x30c/0x730
worker_thread+0x62/0x420
kthread+0x138/0x150
__ret_from_fork+0x3c/0x58
ret_from_fork+0xa/0x40
other info that might help us debug this:
Chain exists of:
(wq_completion)smc_tx_wq-00000000#2
--> smc_client_lgr_pending
--> (work_completion)(&(&lgr->free_work)->work)
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock((work_completion)(&(&lgr->free_work)->work));
lock(smc_client_lgr_pending);
lock((work_completion)
(&(&lgr->free_work)->work));
lock((wq_completion)smc_tx_wq-00000000#2);
*** DEADLOCK ***
2 locks held by kworker/3:0/176251:
#0: 0000000080183548
((wq_completion)events){+.+.}-{0:0},
at: process_one_work+0x232/0x730
#1: 0000037fffe97dc8
((work_completion)
(&(&lgr->free_work)->work)){+.+.}-{0:0},
at: process_one_work+0x232/0x730
stack backtrace:
CPU: 3 PID: 176251 Comm: kworker/3:0 Not tainted
Hardware name: IBM 8561 T01 701 (z/VM 7.2.0)
Call Trace:
[<000000002983c3e4>] dump_stack_lvl+0xac/0x100
[<0000000028b477ae>] check_noncircular+0x13e/0x160
[<0000000028b48808>] check_prev_add+0xd8/0xe88
[<0000000028b49cc4>] validate_chain+0x70c/0xb20
[<0000000028b4bd26>] __lock_acquire+0x58e/0xbd8
[<0000000028b4cf6a>] lock_acquire.part.0+0xe2/0x248
[<0000000028b4d17c>] lock_acquire+0xac/0x1c8
[<0000000028addaaa>] __flush_workqueue+0xaa/0x4f0
[<0000000028addf9a>] drain_workqueue+0xaa/0x158
[<0000000028ae303c>] destroy_workqueue+0x44/0x2d8
[<000003ff8029af26>] smc_lgr_free+0x9e/0xf8 [smc]
[<0000000028adf3d4>] process_one_work+0x30c/0x730
[<0000000028adf85a>] worker_thread+0x62/0x420
[<0000000028aeac50>] kthread+0x138/0x150
[<0000000028a63914>] __ret_from_fork+0x3c/0x58
[<00000000298503da>] ret_from_fork+0xa/0x40
INFO: lockdep is turned off.
===================================================================
This deadlock occurs because cancel_delayed_work_sync() waits for
the work(&lgr->free_work) to finish, while the &lgr->free_work
waits for the work(lgr->tx_wq), which needs the sk_lock-AF_SMC, that
is already used under the mutex_lock.
The solution is to use cancel_delayed_work() instead, which kills
off a pending work.
Fixes: a52bcc919b14 ("net/smc: improve termination processing")
Signed-off-by: Wenjia Zhang <wenjia@xxxxxxxxxxxxx>
Reviewed-by: Jan Karcher <jaka@xxxxxxxxxxxxx>
Reviewed-by: Karsten Graul <kgraul@xxxxxxxxxxxxx>
Reviewed-by: Tony Lu <tonylu@xxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
index 2eafefa15a1ae..f08fcc50fad3c 100644
--- a/net/smc/smc_core.c
+++ b/net/smc/smc_core.c
@@ -1297,7 +1297,7 @@ static void __smc_lgr_terminate(struct smc_link_group *lgr, bool soft)
if (lgr->terminating)
return; /* lgr already terminating */
/* cancel free_work sync, will terminate when lgr->freeing is set */
- cancel_delayed_work_sync(&lgr->free_work);
+ cancel_delayed_work(&lgr->free_work);
lgr->terminating = 1;
/* kill remaining link group connections */
