Analyzing Stalled Drivers and Time-Outs.
When debugging a SCSI miniport driver, the three most common causes for hangs and time-outs are:
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The SCSI miniport DPC is not running
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The SCSI miniport fails to ask for the next request
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A request is not being completed by the SCSI miniport, usually because it is waiting for map registers.
If you suspect that the SCSI miniport DPC is not running, use !pcr to display the DPC queue for the current processor. If the SCSI port DPC routine is in the DPC queue, place a breakpoint on this routine to determine whether this routine is ever called. Otherwise, use !scsikd.scsiext on each device. Consider the following sample output from the !scsikd.scsiext extension:
0: kd> !scsikd.scsiext 86353040 Common Extension: < ..omitted.. > Logical Unit Extension: Address (3, 0, 1, 0) Claimed Enumerated Visible LuFlags (0x00000000): Retry 0x00 Key 0x008889ff Lock 0x00000000 Pause 0x00000000 CurrentLock: 0x00000000 HwLuExt 0x862e6f00 Adapter 0x8633db28 Timeout 0x0000000a NextLun 0x00000000 ReadyLun 0x00000000 Pending 0x00000000 Busy 0x00000000 Untagged 0x00000000 . . . Request list @0x86353200: Tick count is 2526 SrbData 8615d700 Srb 8611f4fc Irp 8611f2b8 Key 60197 <1s SrbData 85e72868 Srb 86100c3c Irp 861009f8 Key e29dc7 <1s
If the timeout slot is -1 and the untagged slot is nonzero, or the time-out slot is nonzero and there are requests shown, the miniport has failed to ask for the next request.
Alternatively, if the retry slot and the busy slot are nonzero, a request may not be completed by the SCSI miniport because it is waiting for map registers. Similarly, if the untagged and pending slots are nonzero, the SCSI miniport might be waiting for map registers. In either case, the address of the SCSI request block (SRB) is the address in the busy slot and the address of the request that is not being completed. For more information about the SRB, use the !minipkd.srb extension with this address as input.
The !devobj extension determines whether the SCSI miniport is waiting for map registers. Use the device object address of the device that is issuing the request as input to !devobj. If the current IRQ is nonzero, it is highly probable that the SCSI miniport is waiting for map registers.
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