From: Chris Wilson <chris@chris-wilson.co.uk>
To: Ben Widawsky <ben@bwidawsk.net>, intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 4/4] drm/i915: optional fewer warning patch
Date: Sat, 09 Apr 2011 23:31:14 +0100 [thread overview]
Message-ID: <849307$cd80vp@azsmga001.ch.intel.com> (raw)
In-Reply-To: <1302381082-3167-5-git-send-email-ben@bwidawsk.net>
On Sat, 9 Apr 2011 13:31:22 -0700, Ben Widawsky <ben@bwidawsk.net> wrote:
> + *
> + * Intelligent users of the interface may do a force_wake_get() followed
> + * by many register reads and writes, knowing that the reference count
> + * is already incremented. So we do not want to warn on those.
> */
Hmm, any place where we touch registers without holding a lock, unless
under exceptional conditions such as !SYSTEM_RUNNING, is a bug waiting to
happen. And probably already happened. Nasty, hard to reproduce race
conditions.
The complication is that some registers will be protected by
dev->config.mode_lock rather than dev->struct_mutex (and a very rare set
are protected by their own irq spinlocks). This sounds like a job for
lockdep... And a lot of documentation. Fortunately, we only have those two
conditions (KMS (detection and mode setting) vs GEM (execution and memory
managment)) and their intersection to worry about.
One of the first steps would be to review all the comments Jesse added to
document the KMS locking and back those up with assertions and updates.
Plenty of work to do before we can feel sure that the locking is sane.
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
next prev parent reply other threads:[~2011-04-09 22:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-08 17:47 forcewake junk, RFC, RFT(test) Ben Widawsky
2011-04-08 17:47 ` [PATCH 1/4] drm/i915: proper use of forcewake Ben Widawsky
2011-04-08 17:47 ` [PATCH 2/4] drm/i915: refcounts for forcewake Ben Widawsky
2011-04-08 17:47 ` [PATCH 3/4] drm/i915: userspace interface to the forcewake refcount Ben Widawsky
2011-04-08 17:47 ` [PATCH 4/4] drm/i915: optional fewer warning patch Ben Widawsky
2011-04-09 20:26 ` forcewake junk, part2 Ben Widawsky
2011-04-09 20:26 ` (no subject) Ben Widawsky
[not found] ` <1302380787-2957-3-git-send-email-ben@bwidawsk.net>
2011-04-09 20:26 ` [PATCH 1/4] drm/i915: proper use of forcewake Ben Widawsky
2011-04-09 20:26 ` [PATCH 2/4] drm/i915: refcounts for forcewake Ben Widawsky
2011-04-09 20:26 ` [PATCH 3/4] drm/i915: userspace interface to the forcewake refcount Ben Widawsky
2011-04-09 20:31 ` forcewake patches (ignore previous, please) Ben Widawsky
2011-04-09 20:31 ` [PATCH 1/4] drm/i915: proper use of forcewake Ben Widawsky
2011-04-09 20:31 ` [PATCH 2/4] drm/i915: refcounts for forcewake Ben Widawsky
2011-04-09 20:31 ` [PATCH 3/4] drm/i915: userspace interface to the forcewake refcount Ben Widawsky
2011-04-09 20:31 ` [PATCH 4/4] drm/i915: optional fewer warning patch Ben Widawsky
2011-04-09 22:31 ` Chris Wilson [this message]
2011-04-09 23:32 ` Ben Widawsky
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