[Bug 11990] New: Kernel hang in spin_unlock_irq from scsi_request_fn from do_IRQ

[bugme-daemon@bugzilla.kernel.org]

http://bugzilla.kernel.org/show_bug.cgi?id=11990

           Summary: Kernel hang in spin_unlock_irq from scsi_request_fn from
                    do_IRQ
           Product: IO/Storage
           Version: 2.5
     KernelVersion: 2.6.28-rc3
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: SCSI
        AssignedTo: linux-scsi@vger.kernel.org
        ReportedBy: vandrove@vc.cvut.cz


Latest working kernel version: commit c8d7aa after 2.6.28-rc2
Earliest failing kernel version: commit 920da6 after 2.6.28-rc2
Distribution: Debian
Hardware Environment: sata_sil24, amd64, 2cpu
Software Environment: 64bit kernel, 32bit userspace, preemptible kernel
Problem Description:

When I/O is under stress, from time to time CPU1 hangs, most probably due to
endless stream of interrupts.  Backtrace printed either by kernel's softlockup
detection or alt-sysrq-p is below (written down; I/O is dead when this
happens).

_spin_unlock_irq + 0x30  (after sti)
scsi_request_fn + 0x1b9  (after spin_unlock_irq(shost->host_lock) at
not_ready:)
blk_invoke_request_fn
__blk_runqueue
scsi_run_queue
scsi_next_command
scsi_end_request
scsi_io_completion
scsi_finish_command
scsi_softirq_done
blk_done_softirq
__do_softirq
call_softirq
do_softirq
irqexit
do_IRQ
ret_from_intr
<EOI>
native_safe_halt
trace_hardirqs_on
default_idle
c1e_idle
cpu_idle
start_secondary

Steps to reproduce:

It seems to occur under heavy I/O (updatedb, dumping core from ~3GB app), but I
was not able to trigger it reliably - most reliable is hard resetting box, then
it occurs in ~80% cases when replaying journals on disks connected to
sata_sil24 (through PMP, but problem does not seem to occur on 2.6.28-rc2 with
Jens's PMP patches).


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