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From:   Chris Wilson <chris@chris-wilson.co.uk>
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To:     airlied@linux.ie, alek.du@intel.com, bin.yang@intel.com,
        daniel@ffwll.ch, dri-devel@lists.freedesktop.org,
        intel-gfx@lists.freedesktop.org, jani.nikula@linux.intel.com,
        jani.saarinen@intel.com, joonas.lahtinen@linux.intel.com,
        linux-kernel@vger.kernel.org, rodrigo.vivi@intel.com
References: <20181220080135.9059-1-bin.yang@intel.com>
In-Reply-To: <20181220080135.9059-1-bin.yang@intel.com>
Message-ID: <154529495460.10782.18092727751160821897@skylake-alporthouse-com>
Subject: Re: [PATCH] drm/i915: Fix i915_gem_wait_for_idle oops due to active_requests
 check
Date:   Thu, 20 Dec 2018 08:35:54 +0000
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Quoting Bin Yang (2018-12-20 08:01:35)
> Normally, i915_request_alloc() and i915_request_add() will be called
> in sequence with drm.struct_mutex locked. But in
> intel_vgpu_create_workload(), it will pre-allocate the request and
> call i915_request_add() in the workload thread for performance
> optimization. The above issue will be triggered.

That's your bug. It's not normally, it's a strict requirement that the
struct_mutex (request generation mutex) be held over the course of
generating the request.
-Chris