[Bug 15095] New: ib_srp module removal triggers circular locking complaint

[Bug 15095] New: ib_srp module removal triggers circular locking complaint

[bugzilla-daemon-590EEB7GvNiWaY/ihj7yzEB+6BGkLq7r]

http://bugzilla.kernel.org/show_bug.cgi?id=15095

           Summary: ib_srp module removal triggers circular locking
                    complaint
           Product: Drivers
           Version: 2.5
    Kernel Version: 2.6.33-rc3 (infiniband.git tree, for-next branch, last
                    commit dates from Thu Jan 14 12:23:37 2010 -0800)
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: Infiniband/RDMA
        AssignedTo: drivers_infiniband-rdma-ztI5WcYan/vQLgFONoPN62D2FQJk+8+b@public.gmane.org
        ReportedBy: bart.vanassche-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
        Regression: No


Created an attachment (id=24662)
 --> (http://bugzilla.kernel.org/attachment.cgi?id=24662)
Kernel log

Removing the ib_srp kernel module often (but not always) triggers a kernel
complaint about a possible circular locking dependency.

That complaint is triggered by the following script:

#!/bin/sh
while [ -e /sys/module/ib_srp ]
do
  rmmod ib_srp || sleep 1
done
modprobe ib_srp "${1:-srp_sg_tablesize=128}"
ibsrpdm -c -d /dev/infiniband/umad0 \
| while read target_info
  do
    echo "${target_info}"
    echo "${target_info}" > /sys/class/infiniband_srp/srp-mlx4_0-1/add_target
done

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Re: [Bug 15095] New: ib_srp module removal triggers circular locking complaint

[Roland Dreier]

Looks like a sysfs problem or maybe a SCSI - sysfs interaction that
doesn't have much to do with ib_srp in particular.  The two locks
involved, namely s_active and attribute_container_mutex, are completely
outside of ib_srp and are taken out of its control.

This is probably triggering now because of the new commit 846f9974
("sysfs: Add lockdep annotations for the sysfs active reference") that
is tracking s_active nesting now.

 - R.
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