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.
