Messages in this thread | | | Date | Tue, 14 Jul 2020 12:26:06 +0800 | From | Can Guo <> | Subject | Re: [PATCH v2 4/4] scsi: ufs: Fix up and simplify error recovery mechanism |
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Hi Bart,
On 2020-07-14 11:52, Bart Van Assche wrote: > On 2020-07-13 19:28, Can Guo wrote: >> o Queue eh_work on a single threaded workqueue to avoid concurrency >> between >> eh_works. > > Please use another approach (mutex?) to serialize error handling. There > are > already way too workqueues in a running Linux system. > >> o According to the UFSHCI JEDEC spec, hibern8 enter/exit error occurs >> when >> the link is broken. This actaully applies to any power mode change >> operations. In this change, if a power mode change operation >> (including >> AH8 enter/exit) fails, mark the link state as UIC_LINK_BROKEN_STATE >> and >> schedule eh_work. eh_work needs to do full reset and restore to >> recover >> the link back to active. Before the link state is recovered to >> active by >> eh_work, any power mode change attempts just return -ENOLINK to >> avoid >> consecutive HW error. >> >> o To avoid concurrency between eh_work and link recovery, remove link >> recovery from hibern8 enter/exit func. If hibern8 enter/exit func >> fails, >> simply return error code and let eh_work run in parallel. >> >> o Recover UFS hba runtime PM error in eh_work. If >> ufschd_suspend/resume >> fails due to UFS error, e.g. hibern8 enter/exit error and SSU cmd >> error, >> the runtime PM framework saves the error to dev.power.runtime_error. >> After that, hba runtime suspend/resume would not be invoked anymore >> until >> dev.power.runtime_error is cleared. The runtime PM error can be >> recovered >> in eh_work by calling pm_runtime_set_active() after reset and >> restore >> succeeds. Meanwhile, if pm_runtime_set_active() returns no error, >> which >> means dev.power.runtime_error is cleared, we also need to explicitly >> resume those scsi devices under hba in case any of them has failed >> to be >> resumed due to hba runtime resume error. >> >> o Fix a racing problem between eh_work and ufshcd_suspend/resume. In >> the >> old code, it blocks scsi requests before schedules eh_work, but when >> eh_work calls pm_runtime_get_sync(), if ufshcd_suspend/resume is >> sending >> a scsi cmd, most likely the SSU cmd, pm_runtime_get_sync() will >> never >> return because scsi requests were blocked. To fix this racing >> problem, >> o Don't block scsi requests before schedule eh_work, but let eh_work >> block scsi requests when eh_work is ready to start error recovery. >> o Meanwhile, if eh_work is schueduled due to fatal error, don't >> requeue >> the scsi cmds sent from ufshcd_suspend/resume path, but simply let >> the >> scsi cmds fail. If the scsi cmds fail, hba runtime suspend/resume >> fails >> too, but it does hurt since eh_work recovers hba runtime PM error. >> >> o Move host/regs dump in ufshcd_check_errors() to eh_work because >> heavy >> dump in IRQ context can lead to stability issues. In addition, some >> clean >> up in ufshcd_print_host_regs() and ufshcd_print_host_state(). > > The above list is a long list. To me that is a sign that this patch > needs to > be split into multiple patches. > > Thanks, > > Bart.
Sure, will split it into a few patches.
Thanks,
Can Guo.
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