[Bug 89321] New: WARN_ON(!in_irq()) warnings from intel_check_page_flip beginning with 3.19-rc1, kernel flag `threadirqs`

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=89321

            Bug ID: 89321
           Summary: WARN_ON(!in_irq()) warnings from intel_check_page_flip
                    beginning with 3.19-rc1, kernel flag `threadirqs`
           Product: DRI
           Version: unspecified
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: minor
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: sakari.m.kapanen at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 113816
  --> https://bugs.freedesktop.org/attachment.cgi?id=113816&action=edit
dmesg.log which shows the warnings

This has been discussed in
http://lists.freedesktop.org/archives/intel-gfx/2015-February/059291.html ,
filing it here so it can be better tracked.

Beginning with kernel 3.19-rc1, there are warnings generated by the i915 from
the function intel_check_page_flip. A dmesg log from boot to the problem with
`drm.debug=13` is attached. This only happens when booting with threaded IRQs
enabled by the `threadirqs` kernel flag. 

As pointed out on the mailing lists, this is probably caused because in_irq()
only tests for real hardware interrupts, not threaded ones. Further information
here: http://lists.freedesktop.org/archives/intel-gfx/2015-February/059623.html

Kernel: 3.19-rc1
Distro: Arch Linux
Machine: Asus Zenbook UX32VD (Intel HD4000 graphics)

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