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    <head>
      <base href="https://bugs.freedesktop.org/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Priority</th>
          <td>medium
          </td>
        </tr>

        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - systemd-udevd hangs with umount loop ISO"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=63218">63218</a>
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>systemd-bugs@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>systemd-udevd hangs with umount loop ISO
          </td>
        </tr>

        <tr>
          <th>QA Contact</th>
          <td>systemd-bugs@lists.freedesktop.org
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux (All)
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>alex_y_xu@yahoo.ca
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>x86-64 (AMD64)
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>general
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>systemd
          </td>
        </tr></table>
      <p>
        <div>
        <pre># cd /tmp
# mkdir ubuntu
# modprobe loop
# mount -o ro,loop,uid=dnsmasq,gid=dnsmasq
~/Downloads/ubuntu-12.10-desktop-amd64.iso ubuntu
<access some files>
# umount ubuntu
^C^C^C^Z^Z^\^\^\<alt-tab>
# echo w > /proc/sysrq-trigger
# journalctl
...
systemd-udevd[68]: worker [1399] /devices/virtual/block/loop0 timeout; kill it
systemd-udevd[68]: seq 1114 '/devices/virtual/block/loop0' killed
kernel: SysRq : Show Blocked State
kernel:   task                        PC stack   pid father        
kernel: umount          D ffff88022fd11140     0  1398   1397 0x00000004    
kernel:  ffff8801edaf9e00 0000000000000086 ffff8801e8979200 0000000000013ea0
kernel:  ffff8801add2ffd8 ffff8801add2ffd8 ffff8801add2ffd8 ffff8801edaf9e00
kernel:  ffff8801bb8cc018 ffff8801bb8cc018 ffff8801bb8cc01c ffff8801edaf9e00
kernel: Call Trace:
kernel:  [<ffffffff813bc449>] ? __mutex_lock_slowpath+0xc9/0x140
kernel:  [<ffffffff813bbfd3>] ? mutex_lock+0x23/0x40
kernel:  [<ffffffffa057327b>] ? loop_clr_fd+0x27b/0x470 [loop]
kernel:  [<ffffffffa05734e0>] ? lo_release+0x70/0x80 [loop]
kernel:  [<ffffffff8110380c>] ? __blkdev_put+0x17c/0x1d0
kernel:  [<ffffffff813bbfc6>] ? mutex_lock+0x16/0x40
kernel:  [<ffffffff810d4f25>] ? deactivate_locked_super+0x55/0x80
kernel:  [<ffffffff810ef843>] ? sys_umount+0xa3/0x3d0
kernel:  [<ffffffff813bf192>] ? system_call_fastpath+0x16/0x1b
kernel: systemd-udevd   D ffff88022fc11140     0  1399     68 0x00000004    
kernel:  ffff8801bb785400 0000000000000086 ffff8801bb781800 00000030706f6f6c
kernel:  ffff8801add83fd8 ffff8801add83fd8 ffff8801add83fd8 ffff8801bb785400
kernel:  ffff8801bb8cc018 ffff8801bb8cc018 ffff8801bb8cc01c ffff8801bb785400
kernel: Call Trace:
kernel:  [<ffffffff813bc449>] ? __mutex_lock_slowpath+0xc9/0x140
kernel:  [<ffffffff813bbfd3>] ? mutex_lock+0x23/0x40
kernel:  [<ffffffff811039f3>] ? __blkdev_get+0x43/0x420
kernel:  [<ffffffff811040a0>] ? blkdev_get+0x2d0/0x2d0
kernel:  [<ffffffff81103f66>] ? blkdev_get+0x196/0x2d0
kernel:  [<ffffffff811040a0>] ? blkdev_get+0x2d0/0x2d0
kernel:  [<ffffffff810d110e>] ? do_dentry_open.isra.18+0x1ee/0x280
kernel:  [<ffffffff810d11b5>] ? finish_open+0x15/0x20
kernel:  [<ffffffff810e014a>] ? do_last.isra.67+0x2fa/0xbf0
kernel:  [<ffffffff810dd508>] ? link_path_walk+0x68/0x830
kernel:  [<ffffffff810e0afb>] ? path_openat.isra.68+0xbb/0x450
kernel:  [<ffffffff810b6432>] ? handle_mm_fault+0x342/0x360
kernel:  [<ffffffff810e10c4>] ? do_filp_open+0x44/0xb0
kernel:  [<ffffffff810ecce2>] ? __alloc_fd+0x42/0x110
kernel:  [<ffffffff810d23d3>] ? do_sys_open+0xf3/0x1e0
kernel:  [<ffffffff813bf192>] ? system_call_fastpath+0x16/0x1b

Don't know if this is a util-linux bug (almost certainly not), loop bug
(probably not), isofs bug (maybe) or systemd bug (seems like it), but
something's definitely not right here.</pre>
        </div>
      </p>
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