New: SCSI Generic READ_10 to SATA fails when starting multiple processes

http://bugzilla.kernel.org/show_bug.cgi?id=15561

           Summary: SCSI Generic READ_10 to SATA fails when starting
                    multiple processes
           Product: IO/Storage
           Version: 2.5
    Kernel Version: 2.6.18-2.6.32
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: SCSI
        AssignedTo: [email protected]
        ReportedBy: [email protected]
        Regression: No

Created an attachment (id=25572)
--> (http://bugzilla.kernel.org/attachment.cgi?id=25572)
aborted sg_io_hdr and kernel logs for various kernels

Issuing a lot of concurrent READ_10 commands via sg driver to SATA drives causes the the commands to be aborted for no good reason. I can reproducibly cause the problem within a few seconds on multiple known good machines and drives over a wide range of kernels.

I queue 16 concurrent 64k reads to each of eight sata drives with eight separate process which start at roughly the same time. At least one and typically several log kernel errors (reset the associated SATA bus) and return task aborted.

Perhaps it is a clue to what is going on: even if just using one drive, driver_duration shows the reads take far longer than normal (greater than 10ms) when first starting to queue io even with only one drive, after which the performance behaves more like one would expect from a sata disk drive. This slow start is exhibited on both arm and x86_64 architectures although with only one drive I've never seen an error.

Older x86_64 kernels are less verbose in kernel log and report with fixed sense instead of sense descriptors, but the same ATA event is occuring. See attachment for typical sg_io_hdr and kernel logs.

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