On Tue, May 11, 2021 at 3:42 AM chenxiang (M) <chenxiang66@xxxxxxxxxxxxx> wrote: > > Re-edit the non-aligned flowchart and add CC to Greg-KH and Saravanna. > > > 在 2021/5/11 11:59, chenxiang (M) 写道: > > Hi Rafael and other guys, > > > > I am trying to add a device link between scsi_host->shost_gendev and > > hisi_hba->dev to support runtime PM for hisi_hba driver > > > > (as it supports runtime PM for scsi host in some scenarios such as > > error handler etc, we can avoid to do them again if adding a > > > > device link between scsi_host->shost_gendev and hisi_hba->dev) as > > follows (hisi_sas driver is under directory drivers/scsi/hisi_sas): > > > > device_link_add(&shost->shost_gendev, hisi_hba->dev, > > DL_FLAG_PM_RUNTIME | DL_FLAG_RPM_ACTIVE) > > > > We have a full test on it, and it works well except when rmmod the > > driver, some call trace occurs as follows: > > > > [root@localhost ~]# rmmod hisi_sas_v3_hw > > [ 105.377944] BUG: scheduling while atomic: kworker/113:1/811/0x00000201 > > [ 105.384469] Modules linked in: bluetooth rfkill ib_isert > > iscsi_target_mod ib_ipoib ib_umad iptable_filter vfio_iommu_type1 > > vfio_pci vfio_virqfd vfio rpcrdma ib_is er > > libiscsi scsi_transport_iscsi crct10dif_ce sbsa_gwdt hns_roce_hw_v2 > > hisi_sec2 hisi_hpre hisi_zip hisi_qm uacce spi_hisi_sfc_v3xx > > hisi_trng_v2 rng_core hisi_uncore _hha_pmu > > hisi_uncore_ddrc_pmu hisi_uncore_l3c_pmu spi_dw_mmio hisi_uncore_pmu > > hns3 hclge hnae3 hisi_sas_v3_hw(-) hisi_sas_main libsas > > [ 105.424841] CPU: 113 PID: 811 Comm: kworker/113:1 Kdump: loaded > > Tainted: G W 5.12.0-rc1+ #1 > > [ 105.434454] Hardware name: Huawei TaiShan 2280 V2/BC82AMDC, BIOS > > 2280-V2 CS V5.B143.01 04/22/2021 > > [ 105.443287] Workqueue: rcu_gp srcu_invoke_callbacks > > [ 105.448154] Call trace: > > [ 105.450593] dump_backtrace+0x0/0x1a4 > > [ 105.454245] show_stack+0x24/0x40 > > [ 105.457548] dump_stack+0xc8/0x104 > > [ 105.460939] __schedule_bug+0x68/0x80 > > [ 105.464590] __schedule+0x73c/0x77c > > [ 105.465700] BUG: scheduling while atomic: kworker/96:1/791/0x00000201 > > [ 105.468066] schedule+0x7c/0x110 > > [ 105.468068] schedule_timeout+0x194/0x1d4 > > [ 105.474490] Modules linked in: > > [ 105.477692] wait_for_completion+0x8c/0x12c > > [ 105.477695] rcu_barrier+0x1e0/0x2fc > > [ 105.477697] scsi_host_dev_release+0x50/0xf0 > > [ 105.477701] device_release+0x40/0xa0 > > [ 105.477704] kobject_put+0xac/0x100 > > [ 105.477707] __device_link_free_srcu+0x50/0x74 > > [ 105.477709] srcu_invoke_callbacks+0x108/0x1a4 > > [ 105.484743] process_one_work+0x1dc/0x48c > > [ 105.492468] worker_thread+0x7c/0x464 > > [ 105.492471] kthread+0x168/0x16c > > [ 105.492473] ret_from_fork+0x10/0x18 > > ... > > > > After analyse the process, we find that it will > > device_del(&shost->gendev) in function scsi_remove_host() and then > > > > put_device(&shost->shost_gendev) in function scsi_host_put() when > > removing the driver, if there is a link between shost and hisi_hba->dev, > > > > it will try to delete the link in device_del(), and also will > > call_srcu(__device_link_free_srcu) to put_device() link->consumer and > > supplier. > > > > But if put device() for shost_gendev in device_link_free() is later > > than in scsi_host_put(), it will call scsi_host_dev_release() in > > > > srcu_invoke_callbacks() while it is atomic and there are scheduling in > > scsi_host_dev_release(), > > > > so it reports the BUG "scheduling while atomic:...". > > > > thread 1 thread2 > > hisi_sas_v3_remove > > ... > > sas_remove_host() > > ... > > scsi_remove_host() > > ... > > device_del(&shost->shost_gendev) > > ... > > device_link_purge() > > __device_link_del() > > device_unregister(&link->link_dev) > > devlink_dev_release > > call_srcu(__device_link_free_srcu) -----------> > > srcu_invoke_callbacks (atomic) > > __device_link_free_srcu > > ... > > scsi_host_put() > > put_device(&shost->shost_gendev) (ref = 1) > > device_link_free() > > put_device(link->consumer) > > //shost->gendev ref = 0 > > ... > > scsi_host_dev_release > > ... > > rcu_barrier > > kthread_stop() > > Re-edit the non-aligned flowchart > thread 1 thread 2 > hisi_sas_v3_remove() > ... > sas_remove_host() > ... > device_del(&shost->shost_gendev) > ... > device_link_purge() > __device_link_del() > device_unregister(&link->link_dev) > devlink_dev_release > call_srcu(__device_link_free_srcu) -----------> > srcu_invoke_callbacks (atomic) > __device_link_free_srcu() > ... > scsi_host_put() > put_device(&shost->shost_gendev) (ref = 1) > device_link_free() > put_device(link->consumer) > //shost->gendev ref = 0 > ... > scsi_host_dev_release() > ... > rcu_barrier() > kthread_stop() > > > > > > > We can check kref of shost->shost_gendev to make sure scsi_host_put() > > to release scsi host device in LLDD driver to avoid the issue, > > > > but it seems be a common issue: function __device_link_free_srcu > > calls put_device() for consumer and supplier, > > > > but if it's ref =0 at that time and there are scheduling or sleep in > > dev_release, it may have the issue. > > > > Do you have any idea about the issue? Another report for the same issue. https://lore.kernel.org/lkml/CAGETcx80xSZ8d4JbZqiSz4L0VNtL+HCnFCS2u3F9aNC0QQoQjg@xxxxxxxxxxxxxx/ I don't have enough context yet about the need for SRCU (I haven't read up all the runtime PM code), but this is a real issue that needs to be solved. Dirty/terrible hack is to kick off another work to do the put_device(). But is there any SRCU option that'll try to do the release in a non-atomic context? -Saravana
