From: Jens Remus <jremus@xxxxxxxxxxxxx>
Otherwise iterating with list_for_each() over the adapter->erp_ready_head
and adapter->erp_running_head lists can lead to an infinite loop. See
commit "zfcp: fix infinite iteration on erp_ready_head list".
The run-time check is only performed for debug kernels which have the
kernel lock validator enabled. Following is an example of the warning that
is reported, if the ERP lock is not held when calling zfcp_dbf_rec_trig():
WARNING: CPU: 0 PID: 604 at drivers/s390/scsi/zfcp_dbf.c:288 zfcp_dbf_rec_trig+0x172/0x188
Modules linked in: ...
CPU: 0 PID: 604 Comm: kworker/u128:3 Not tainted 4.16.0-... #1
Hardware name: IBM 2964 N96 702 (z/VM 6.4.0)
Workqueue: zfcp_q_0.0.1906 zfcp_scsi_rport_work
Krnl PSW : 00000000330fdbf9 00000000367e9728 (zfcp_dbf_rec_trig+0x172/0x188)
R:0 T:1 IO:1 EX:1 Key:0 M:1 W:0 P:0 AS:3 CC:3 PM:0 RI:0 EA:3
Krnl GPRS: 00000000c57a5d99 3288200000000000 0000000000000000 000000006cc82740
00000000009d09d6 0000000000000000 00000000000000ff 0000000000000000
0000000000000000 0000000000e1b5fe 000000006de01d38 0000000076130958
000000006cc82548 000000006de01a98 00000000009d09d6 000000006a6d3c80
Krnl Code: 00000000009d0ad2: eb7ff0b80004 lmg %r7,%r15,184(%r15)
00000000009d0ad8: c0f4000d7dd0 brcl 15,b80678
#00000000009d0ade: a7f40001 brc 15,9d0ae0
>00000000009d0ae2: a7f4ff7d brc 15,9d09dc
00000000009d0ae6: e340f0f00004 lg %r4,240(%r15)
00000000009d0aec: eb7ff0b80004 lmg %r7,%r15,184(%r15)
00000000009d0af2: 07f4 bcr 15,%r4
00000000009d0af4: 0707 bcr 0,%r7
Call Trace:
([<00000000009d09d6>] zfcp_dbf_rec_trig+0x66/0x188)
[<00000000009dd740>] zfcp_scsi_rport_work+0x98/0x190
[<0000000000169b34>] process_one_work+0x3d4/0x6f8
[<000000000016a08a>] worker_thread+0x232/0x418
[<000000000017219e>] kthread+0x166/0x178
[<0000000000b815ea>] kernel_thread_starter+0x6/0xc
[<0000000000b815e4>] kernel_thread_starter+0x0/0xc
2 locks held by kworker/u128:3/604:
#0: ((wq_completion)name){+.+.}, at: [<0000000082af1024>] process_one_work+0x1dc/0x6f8
#1: ((work_completion)(&port->rport_work)){+.+.}, at: [<0000000082af1024>] process_one_work+0x1dc/0x6f8
Last Breaking-Event-Address:
[<00000000009d0ade>] zfcp_dbf_rec_trig+0x16e/0x188
---[ end trace b2f4020572e2c124 ]---
Suggested-by: Steffen Maier <maier@xxxxxxxxxxxxx>
Signed-off-by: Jens Remus <jremus@xxxxxxxxxxxxx>
Reviewed-by: Benjamin Block <bblock@xxxxxxxxxxxxx>
Reviewed-by: Steffen Maier <maier@xxxxxxxxxxxxx>
Signed-off-by: Steffen Maier <maier@xxxxxxxxxxxxx>
---
drivers/s390/scsi/zfcp_dbf.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/s390/scsi/zfcp_dbf.c b/drivers/s390/scsi/zfcp_dbf.c
index bb3373260169..781141bf2c28 100644
--- a/drivers/s390/scsi/zfcp_dbf.c
+++ b/drivers/s390/scsi/zfcp_dbf.c
@@ -285,6 +285,8 @@ void zfcp_dbf_rec_trig(char *tag, struct zfcp_adapter *adapter,
struct list_head *entry;
unsigned long flags;
+ lockdep_assert_held(&adapter->erp_lock);
+
if (unlikely(!debug_level_enabled(dbf->rec, level)))
return;
--
2.16.3
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