This patch fixes an unbalanced refcount issue. Elevating the lock for both kref_put and also for controller node deletion. Previously, controller deletion was protected but the not the kref_put. This was causing the other thread to pick up the controller structure which was already kref'd zero. This was causing the following BUG_ON and also sometimes panic. WARNING: at lib/kref.c:43 kref_get+0x2d/0x30() (Not tainted) Hardware name: IBM System x3655 -[7985AC1]- Modules linked in: fuse scsi_dh_rdac autofs4 nfs lockd fscache nfs_acl auth_rpcgss sunrpc 8021q garp stp llc ipv6 ib_srp(U) scsi_transport_srp scsi_tgt ib_cm(U) ib_sa(U) ib_uverbs(U) ib_umad(U) mlx4_ib(U) mlx4_core(U) ib_mthca(U) ib_mad(U) ib_core(U) dm_mirror dm_region_hash dm_log dm_round_robin dm_multipath uinput bnx2 ses enclosure sg ibmpex ibmaem ipmi_msghandler serio_raw k8temp hwmon amd64_edac_mod edac_core edac_mce_amd shpchp i2c_piix4 ext4 mbcache jbd2 sr_mod cdrom sd_mod crc_t10dif sata_svw pata_acpi ata_generic pata_serverworks aacraid radeon ttm drm_kms_helper drm i2c_algo_bit i2c_core dm_mod [last unloaded: freq_table] Pid: 13735, comm: srp_daemon Not tainted 2.6.32-71.el6.x86_64 #1 Call Trace: [<ffffffff8106b857>] warn_slowpath_common+0x87/0xc0 [<ffffffff8106b8aa>] warn_slowpath_null+0x1a/0x20 [<ffffffff8125c39d>] kref_get+0x2d/0x30 [<ffffffffa01b4029>] rdac_bus_attach+0x459/0x580 [scsi_dh_rdac] [<ffffffff8135232a>] scsi_dh_handler_attach+0x2a/0x80 [<ffffffff81352c7b>] scsi_dh_notifier+0x9b/0xa0 [<ffffffff814cd7a5>] notifier_call_chain+0x55/0x80 [<ffffffff8109711a>] __blocking_notifier_call_chain+0x5a/0x80 [<ffffffff81097156>] blocking_notifier_call_chain+0x16/0x20 [<ffffffff8132bec5>] device_add+0x515/0x640 [<ffffffff813329e4>] ? attribute_container_device_trigger+0xc4/0xe0 [<ffffffff8134f659>] scsi_sysfs_add_sdev+0x89/0x2c0 [<ffffffff8134d096>] scsi_probe_and_add_lun+0xea6/0xed0 [<ffffffff8134beb2>] ? scsi_alloc_target+0x292/0x2d0 [<ffffffff8134d1e1>] __scsi_scan_target+0x121/0x750 [<ffffffff811df806>] ? sysfs_create_file+0x26/0x30 [<ffffffff8132b759>] ? device_create_file+0x19/0x20 [<ffffffff81332838>] ? attribute_container_add_attrs+0x78/0x90 [<ffffffff814b008c>] ? klist_next+0x4c/0xf0 [<ffffffff81332e30>] ? transport_configure+0x0/0x20 [<ffffffff813329e4>] ? attribute_container_device_trigger+0xc4/0xe0 [<ffffffff8134df40>] scsi_scan_target+0xd0/0xe0 [<ffffffffa02f053a>] srp_create_target+0x75a/0x890 [ib_srp] [<ffffffff8132a130>] dev_attr_store+0x20/0x30 [<ffffffff811df145>] sysfs_write_file+0xe5/0x170 [<ffffffff8116c818>] vfs_write+0xb8/0x1a0 [<ffffffff810d40a2>] ? audit_syscall_entry+0x272/0x2a0 [<ffffffff8116d251>] sys_write+0x51/0x90 [<ffffffff81013172>] system_call_fastpath+0x16/0x1b Signed-off-by: Babu Moger <babu.moger@xxxxxxxxxx> Acked-by: Mike Snitzer <snitzer@xxxxxxxxxx> --- --- linux-3.3-rc1-new/drivers/scsi/device_handler/scsi_dh_rdac.c.orig 2012-01-19 17:04:48.000000000 -0600 +++ linux-3.3-rc1-new/drivers/scsi/device_handler/scsi_dh_rdac.c 2012-02-01 10:50:31.000000000 -0600 @@ -364,10 +364,7 @@ static void release_controller(struct kr struct rdac_controller *ctlr; ctlr = container_of(kref, struct rdac_controller, kref); - flush_workqueue(kmpath_rdacd); - spin_lock(&list_lock); list_del(&ctlr->node); - spin_unlock(&list_lock); kfree(ctlr); } @@ -376,20 +373,17 @@ static struct rdac_controller *get_contr { struct rdac_controller *ctlr, *tmp; - spin_lock(&list_lock); - list_for_each_entry(tmp, &ctlr_list, node) { if ((memcmp(tmp->array_id, array_id, UNIQUE_ID_LEN) == 0) && (tmp->index == index) && (tmp->host == sdev->host)) { kref_get(&tmp->kref); - spin_unlock(&list_lock); return tmp; } } ctlr = kmalloc(sizeof(*ctlr), GFP_ATOMIC); if (!ctlr) - goto done; + return NULL; /* initialize fields of controller */ memcpy(ctlr->array_id, array_id, UNIQUE_ID_LEN); @@ -405,8 +399,7 @@ static struct rdac_controller *get_contr INIT_WORK(&ctlr->ms_work, send_mode_select); INIT_LIST_HEAD(&ctlr->ms_head); list_add(&ctlr->node, &ctlr_list); -done: - spin_unlock(&list_lock); + return ctlr; } @@ -517,9 +510,12 @@ static int initialize_controller(struct index = 0; else index = 1; + + spin_lock(&list_lock); h->ctlr = get_controller(index, array_name, array_id, sdev); if (!h->ctlr) err = SCSI_DH_RES_TEMP_UNAVAIL; + spin_unlock(&list_lock); } return err; } @@ -906,7 +902,9 @@ static int rdac_bus_attach(struct scsi_d return 0; clean_ctlr: + spin_lock(&list_lock); kref_put(&h->ctlr->kref, release_controller); + spin_unlock(&list_lock); failed: kfree(scsi_dh_data); @@ -921,14 +919,19 @@ static void rdac_bus_detach( struct scsi struct rdac_dh_data *h; unsigned long flags; - spin_lock_irqsave(sdev->request_queue->queue_lock, flags); scsi_dh_data = sdev->scsi_dh_data; + h = (struct rdac_dh_data *) scsi_dh_data->buf; + if (h->ctlr && h->ctlr->ms_queued) + flush_workqueue(kmpath_rdacd); + + spin_lock_irqsave(sdev->request_queue->queue_lock, flags); sdev->scsi_dh_data = NULL; spin_unlock_irqrestore(sdev->request_queue->queue_lock, flags); - h = (struct rdac_dh_data *) scsi_dh_data->buf; + spin_lock(&list_lock); if (h->ctlr) kref_put(&h->ctlr->kref, release_controller); + spin_unlock(&list_lock); kfree(scsi_dh_data); module_put(THIS_MODULE); sdev_printk(KERN_NOTICE, sdev, "%s: Detached\n", RDAC_NAME); -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel