Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: Qestion about device link | From | "chenxiang (M)" <> | Date | Wed, 12 May 2021 11:24:53 +0800 |
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Hi Rafael,
在 2021/5/12 3:16, Rafael J. Wysocki 写道: > On Tuesday, May 11, 2021 4:39:31 PM CEST Rafael J. Wysocki wrote: >> On 5/11/2021 5:59 AM, chenxiang (M) wrote: >>> 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() >>> >>> >>> 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? >>> >> Yes, this is a general issue. >> >> If I'm not mistaken, it can be addressed by further deferring the >> device_link_free() invocation through a workqueue. >> >> Let me cut a patch doing this. > Please test the patch below and let me know if it works for you.
I have a test on the patch, and it solves my issue.
> > --- > drivers/base/core.c | 18 ++++++++++++++++-- > include/linux/device.h | 5 ++++- > 2 files changed, 20 insertions(+), 3 deletions(-) > > Index: linux-pm/drivers/base/core.c > =================================================================== > --- linux-pm.orig/drivers/base/core.c > +++ linux-pm/drivers/base/core.c > @@ -455,16 +455,30 @@ static void device_link_free(struct devi > } > > #ifdef CONFIG_SRCU > +static void __device_link_free_fn(struct work_struct *work) > +{ > + device_link_free(container_of(work, struct device_link, srcu.work)); > +} > + > static void __device_link_free_srcu(struct rcu_head *rhead) > { > - device_link_free(container_of(rhead, struct device_link, rcu_head)); > + struct device_link *link = container_of(rhead, struct device_link, > + srcu.rhead); > + struct work_struct *work = &link->srcu.work; > + > + /* > + * Because device_link_free() may sleep in some cases, schedule the > + * execution of it instead of invoking it directly. > + */ > + INIT_WORK(work, __device_link_free_fn); > + schedule_work(work); > } > > static void devlink_dev_release(struct device *dev) > { > struct device_link *link = to_devlink(dev); > > - call_srcu(&device_links_srcu, &link->rcu_head, __device_link_free_srcu); > + call_srcu(&device_links_srcu, &link->srcu.rhead, __device_link_free_srcu); > } > #else > static void devlink_dev_release(struct device *dev) > Index: linux-pm/include/linux/device.h > =================================================================== > --- linux-pm.orig/include/linux/device.h > +++ linux-pm/include/linux/device.h > @@ -584,7 +584,10 @@ struct device_link { > refcount_t rpm_active; > struct kref kref; > #ifdef CONFIG_SRCU > - struct rcu_head rcu_head; > + union { > + struct rcu_head rhead; > + struct work_struct work; > + } srcu; > #endif > bool supplier_preactivated; /* Owned by consumer probe. */ > }; > > > > > . >
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