Daniel Vetter 6005ce4243 drm/i915: close tiny race in the ilk pcu even interrupt setup
By the time we write DEIER in the postinstall hook the interrupt
handler could run any time. And it does modify DEIER to handle
interrupts.

Hence the DEIER read-modify-write cycle for enabling the PCU event
source is racy. Close this races the same way we handle vblank
interrupts: Unconditionally enable the interrupt in the IER register,
but conditionally mask it in IMR. The later poses no such race since
the interrupt handler does not touch DEIMR.

Also update the comment, the clearing has already happened
unconditionally above.

v2: Actually shove the updated comment into the right train^W commit,
as spotted by Paulo.

Cc: Paulo Zanoni <przanoni@gmail.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
2013-07-01 11:14:55 +02:00
..
2013-06-28 12:04:04 +10:00
2013-06-28 12:04:05 +10:00
2013-02-19 17:57:44 -05:00
2013-06-28 12:04:06 +10:00
2013-02-27 19:10:16 -08:00
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2013-02-27 19:10:15 -08:00
2013-04-30 15:15:58 +02:00
2013-04-30 22:20:00 +02:00
2013-06-24 06:26:50 +10:00

************************************************************
* For the very latest on DRI development, please see:      *
*     http://dri.freedesktop.org/                          *
************************************************************

The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).

The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:

    1. The DRM provides synchronized access to the graphics hardware via
       the use of an optimized two-tiered lock.

    2. The DRM enforces the DRI security policy for access to the graphics
       hardware by only allowing authenticated X11 clients access to
       restricted regions of memory.

    3. The DRM provides a generic DMA engine, complete with multiple
       queues and the ability to detect the need for an OpenGL context
       switch.

    4. The DRM is extensible via the use of small device-specific modules
       that rely extensively on the API exported by the DRM module.


Documentation on the DRI is available from:
    http://dri.freedesktop.org/wiki/Documentation
    http://sourceforge.net/project/showfiles.php?group_id=387
    http://dri.sourceforge.net/doc/

For specific information about kernel-level support, see:

    The Direct Rendering Manager, Kernel Support for the Direct Rendering
    Infrastructure
    http://dri.sourceforge.net/doc/drm_low_level.html

    Hardware Locking for the Direct Rendering Infrastructure
    http://dri.sourceforge.net/doc/hardware_locking_low_level.html

    A Security Analysis of the Direct Rendering Infrastructure
    http://dri.sourceforge.net/doc/security_low_level.html