On 06/14/2017 09:33 AM, Yijing Wang wrote: > Libsas complete a hotplug event notified by LLDD in several works, > for example, if libsas receive a PHYE_LOSS_OF_SIGNAL, we process it > in following steps: > > notify_phy_event [interrupt context] > sas_queue_event [queue work on shost->work_q] > sas_phye_loss_of_signal [running in shost->work_q] > sas_deform_port [remove sas port] > sas_unregister_dev > sas_discover_event [queue destruct work on shost->work_q tail] > > In above case, complete whole hotplug in two works, remove sas port first, then > put the destruction of device in another work and queue it on in the tail of > workqueue, since sas port is the parent of the children rphy device, so if remove > sas port first, the children rphy device would also be deleted, when the destruction > work coming, it would find the target has been removed already, and report a > sysfs warning calltrace. > > queue tail queue head > DISCE_DESTRUCT----> PORTE_BYTES_DMAED event ----->PHYE_LOSS_OF_SIGNAL[running] > > There are other hotplug issues in current framework, in above case, if there is > hotadd sas event queued between hotremove works, the hotplug order would be broken > and unexpected issues would happen. > > In this patch, we try to solve these issues in following steps: > 1. create a new workqueue used to run sas event work, instead of scsi host workqueue, > because we may block sas event work, we cannot block the normal scsi works. > When libsas receive a phy down event, sas_deform_port would be called, and now we > block sas_deform_port and wait for destruction work finish, in sas_destruct_devices, > we may wait ata error handler, it would take a long time, so if do all stuff in scsi > host workq, libsas may block other scsi works too long. > 2. create a new workqueue used to run sas discovery events work, instead of scsi host > workqueue, because in some cases, eg. in revalidate domain event, we may unregister > a sas device and discover new one, we must sync the execution, wait the remove process > finish, then start a new discovery. So we must put the probe and destruct discovery > events in a new workqueue to avoid deadlock. > 3. introudce a asd_sas_port level wait-complete and a sas_discovery level wait-complete > we use former wait-complete to achieve a sas event atomic process and use latter to > make a sas discovery sync. > 4. remove disco_mutex in sas_revalidate_domain, since now sas_revalidate_domain sync > the destruct discovery event execution, it's no need to lock disco mutex there. The way you've written the changelog suggests this patch should be split into 4 patches, each one taking care of one of your change items. -- Johannes Thumshirn Storage jthumshirn@xxxxxxx +49 911 74053 689 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg GF: Felix Imendörffer, Jane Smithard, Graham Norton HRB 21284 (AG Nürnberg) Key fingerprint = EC38 9CAB C2C4 F25D 8600 D0D0 0393 969D 2D76 0850
