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      <base href="https://bugs.freedesktop.org/" />
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        <tr>
          <th>Priority</th>
          <td>medium
          </td>
        </tr>

        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - [GM45 regression] system hang while booting up"
   href="https://bugs.freedesktop.org/show_bug.cgi?id=59750">59750</a>
          </td>
        </tr>

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

        <tr>
          <th>Summary</th>
          <td>[GM45 regression] system hang while booting up
          </td>
        </tr>

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

        <tr>
          <th>Severity</th>
          <td>critical
          </td>
        </tr>

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

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>cancan.feng@intel.com
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Other
          </td>
        </tr>

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

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

        <tr>
          <th>Component</th>
          <td>DRM/Intel
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>DRI
          </td>
        </tr></table>
      <p>
        <div>
        <pre>branch name: drm-kms-locking


Description:
----------------------------------------
We tested nightly, found machine hang while booting after grub.Then the screen
turned into black. I can't login by ssh. We found this issue caused by "branch
drm-kms-locking". The commit I listed below is first bad.

Bisect result:
------------------------------------------
commit 7b24056be6db7ce907baffdd4cf142ab774ea60c 
Author: Daniel Vetter <<a href="mailto:daniel.vetter@ffwll.ch">daniel.vetter@ffwll.ch</a>>
Date:   Wed Dec 12 00:35:33 2012 +0100

    drm: don't hold crtc mutexes for connector ->detect callbacks

    The coup de grace of the entire journey. No more dropped frames every
    10s on my testbox!

    I've tried to audit all ->detect and ->get_modes callbacks, but things
    became a bit fuzzy after trying to piece together the umpteenth
    implemenation. Afaict most drivers just have bog-standard output
    register frobbing with a notch of i2c edid reading, nothing which
    could potentially race with the newly concurrent pageflip/set_cursor
    code. The big exception is load-detection code which requires a
    running pipe, but radeon/nouveau seem to to this without touching any
    state which can be observed from page_flip (e.g. disabled crtcs
    temporarily getting enabled and so a pageflip succeeding).</pre>
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