Re: REQ_PM vs REQ_TYPE_PM_RESUME

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On 12/16/2013 06:30 PM, Phillip Susi wrote:
> For some reason, the system hangs on resume if I issue the REQUEST
> SENSE command after blk_pre_runtime_suspend.  My understanding is
> that the REQ_PM flag should make the command process even though
> the queue is RPM_SUSPENDING, but it doesn't seem to work.  Anyone
> have any idea why?

So I found the problem but I'm confused by it.  I thought that the
REQ_PM flag was supposed to make sure the request was dispatched even
though the device was still suspended ( or suspending ).  It seems
that this is not the case, and only requests with the type set to
REQ_TYPE_PM_RESUME are dispatched during suspend/resume.  The
following patch fixes the hang, but I'm not sure why it is needed or
if it is generally appropriate:

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 7bd7f0d..c5ce50d 100644
- --- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -227,7 +227,9 @@ int scsi_execute(struct scsi_device *sdev, const
unsigned char *cmd,
        req->sense_len = 0;
        req->retries = retries;
        req->timeout = timeout;
- -       req->cmd_type = REQ_TYPE_BLOCK_PC;
+       if (flags & REQ_PM)
+               req->cmd_type = REQ_TYPE_PM_RESUME;
+       else req->cmd_type = REQ_TYPE_BLOCK_PC;
        req->cmd_flags |= flags | REQ_QUIET | REQ_PREEMPT;

        /*


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