From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Wilson Subject: Re: [PATCH 2/2] drm/i915: provide module parameter description Date: Thu, 07 Jul 2011 10:17:52 +0100 Message-ID: References: <1309990493-27160-1-git-send-email-ben@bwidawsk.net> <1309990493-27160-2-git-send-email-ben@bwidawsk.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mga09.intel.com (mga09.intel.com [134.134.136.24]) by gabe.freedesktop.org (Postfix) with ESMTP id D96249F616 for ; Thu, 7 Jul 2011 02:17:55 -0700 (PDT) In-Reply-To: <1309990493-27160-2-git-send-email-ben@bwidawsk.net> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Ben Widawsky , intel-gfx@lists.freedesktop.org Cc: Julien Cristau List-Id: intel-gfx@lists.freedesktop.org On Wed, 6 Jul 2011 15:14:53 -0700, Ben Widawsky wrote: > bool i915_enable_hangcheck __read_mostly = true; > module_param_named(enable_hangcheck, i915_enable_hangcheck, bool, 0644); > +MODULE_PARM_DESC(enable_hangcheck, "Periodically check GPU activity for " > + "detecting hangs (default: true)"); I think we need to stress here that disabling the hangcheck can cause the system to hang (X, VT switching, etc) following an GPU hang. The assumption that the hangcheck will prevail and break any waits (and eventually release the struct_mutex) is deeply ingrained into the code. The alternate scenario is to wait without the mutex, which then requires revalidating all state after a wait, effectively we would have to restart the operation from the being. And introduces unfairness (potential starvation) into command/resource allocations... -Chris -- Chris Wilson, Intel Open Source Technology Centre