From: Wenjia Zhang wenjia@linux.ibm.com
[ 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@linux.ibm.com Reviewed-by: Jan Karcher jaka@linux.ibm.com Reviewed-by: Karsten Graul kgraul@linux.ibm.com Reviewed-by: Tony Lu tonylu@linux.alibaba.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/smc/smc_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
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 */