All of lore.kernel.org
 help / color / mirror / Atom feed
From: Jeff McGee <jeff.mcgee@intel.com>
To: intel-gfx@lists.freedesktop.org
Cc: kalyan.kondapally@intel.com, ben@bwidawsk.net
Subject: Re: [RFC 7/8] drm/i915: Skip CSB processing on invalid CSB tail
Date: Wed, 21 Mar 2018 10:31:45 -0700	[thread overview]
Message-ID: <20180321173145.GD19343@jeffdesk> (raw)
In-Reply-To: <20180321172625.6415-8-jeff.mcgee@intel.com>

On Wed, Mar 21, 2018 at 10:26:24AM -0700, jeff.mcgee@intel.com wrote:
> From: Jeff McGee <jeff.mcgee@intel.com>
> 
> Engine reset is fast. A context switch interrupt may be generated just
> prior to the reset such that the top half handler is racing with reset
> post-processing. The handler may set the irq_posted bit again after
> the reset code has cleared it to start fresh. Then the re-enabled
> tasklet will read the CSB head and tail from MMIO, which will be at
> the hardware reset values of 0 and 7 respectively, given that no
> actual CSB event has occurred since the reset. Mayhem then ensues as
> the tasklet starts processing invalid CSB entries.
> 
> We can handle this corner case without adding any new synchronization
> between the irq top half and the reset work item. The tasklet can
> just skip CSB processing if the tail is not sane.
> 
> Signed-off-by: Jeff McGee <jeff.mcgee@intel.com>
> ---
If I drop this patch and substitute https://patchwork.freedesktop.org/patch/211831/
I will see irq_posted get set after reset which causes the first tasklet
run to re-process a previous CSB event and hit GEM_BUG_ON that nothing
was active.
-Jeff
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

  reply	other threads:[~2018-03-21 17:46 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-21 17:26 [RFC 0/8] Force preemption jeff.mcgee
2018-03-21 17:26 ` [RFC 1/8] drm/i915/execlists: Refactor out complete_preempt_context() jeff.mcgee
2018-03-21 17:26 ` [RFC 2/8] drm/i915: Add control flags to i915_handle_error() jeff.mcgee
2018-03-21 17:26 ` [RFC 3/8] drm/i915: Move engine reset prepare/finish to backends jeff.mcgee
2018-03-21 17:26 ` [RFC 4/8] drm/i915: Split execlists/guc reset prepartions jeff.mcgee
2018-03-21 17:26 ` [RFC 5/8] drm/i915/execlists: Flush pending preemption events during reset jeff.mcgee
2018-03-21 17:26 ` [RFC 6/8] drm/i915: Fix loop on CSB processing jeff.mcgee
2018-03-21 17:33   ` Jeff McGee
2018-03-21 18:06     ` Chris Wilson
2018-03-21 18:29       ` Jeff McGee
2018-03-21 19:04         ` Chris Wilson
2018-03-21 17:26 ` [RFC 7/8] drm/i915: Skip CSB processing on invalid CSB tail jeff.mcgee
2018-03-21 17:31   ` Jeff McGee [this message]
2018-03-21 18:12     ` Chris Wilson
2018-03-21 19:06       ` Chris Wilson
2018-03-21 17:26 ` [RFC 8/8] drm/i915: Force preemption to complete via engine reset jeff.mcgee
2018-03-21 18:50 ` ✗ Fi.CI.BAT: failure for Force preemption (rev2) Patchwork
2018-03-22  9:22 ` [RFC 0/8] Force preemption Tvrtko Ursulin
2018-03-22  9:28   ` Chris Wilson
2018-03-22 14:34     ` Jeff McGee
2018-03-22 15:35       ` Chris Wilson
2018-03-22 15:44         ` Jeff McGee
2018-03-22 15:57       ` Tvrtko Ursulin
2018-03-22 16:01         ` Jeff McGee
2018-03-22 17:41           ` Tvrtko Ursulin
2018-03-22 19:08             ` Jeff McGee
2018-03-22 19:59               ` Bloomfield, Jon
2018-03-23 13:20                 ` Joonas Lahtinen
2018-03-23 13:37                   ` Chris Wilson

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20180321173145.GD19343@jeffdesk \
    --to=jeff.mcgee@intel.com \
    --cc=ben@bwidawsk.net \
    --cc=intel-gfx@lists.freedesktop.org \
    --cc=kalyan.kondapally@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.