Messages in this thread | | | Date | Tue, 14 Jul 2020 17:13:16 +0800 | From | Can Guo <> | Subject | Re: [PATCH v2 4/4] scsi: ufs: Fix up and simplify error recovery mechanism |
| |
Hi Bart,
On 2020-07-14 12:26, Can Guo wrote: > 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. >>
Yeah, mutex works, but in this change, we need to flush the eh_work. As per test, in real cases, flush_work can trigger warnings if the work is queued on system_wq. Please check func check_flush_dependency().
>>> 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.
I tried, but I find it hard to split it as it works as a whole, it is a refactor change rather than a mixture of multiple fixes. I will try to refine the commit msg in next version. So it goes just as it is now.
Thanks,
Can Guo.
| |