Messages in this thread | | | Date | Tue, 25 May 2021 10:04:23 +0800 | From | Can Guo <> | Subject | Re: [PATCH v2 5/6] scsi: ufs: Let host_sem cover the entire system suspend/resume |
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Hi Bart,
On 2021-05-25 00:56, Bart Van Assche wrote: > On 5/24/21 1:47 AM, Can Guo wrote: >> UFS error handling now is doing more than just re-probing, but also >> sending >> scsi cmds, e.g., for clearing UACs, and recovering runtime PM error, >> which >> may change runtime status of scsi devices. To protect system >> suspend/resume >> from being disturbed by error handling, move the host_sem from wl pm >> ops >> to ufshcd_suspend_prepare() and ufshcd_resume_complete(). > > Other SCSI LLDs can perform error handling while system suspend/resume > is in progress. Why can't the UFS driver do this?
I don't know about other SCSI LLDs, but UFS error handling is basically doing a re-probe/re-initialization to UFS device. Having UFS error handling running in parallel with system suspend/resume, neither of them will end up well.
I didn't design all this, it is just happening, I am trying to fix it and semaphore works well for me. I am really glad to see someone cares about error handling and fix it with better ideas (maybe using WQ_FREEZABLE) later.
> > Additionally, please document what the purpose of host_sem is before > making any changes to how host_sem is used. The only documentation I > have found of host_sem is the following: "* @host_sem: semaphore used > to > serialize concurrent contexts". To me that text is less than useful > since semaphores are almost always used to serialize concurrent code. >
Sure, host_sem is actually preventing cocurrency happens among any of contexts, such as sysfs access, shutdown, error handling, system suspend/resume and async probe, I will update its message in next version.
Thanks,
Can Guo.
> Thanks, > > Bart.
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