<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEEDINFO " title="NEEDINFO - i915 slab shrink cause a panic" href="https://bugs.freedesktop.org/show_bug.cgi?id=109005#c7">Comment # 7</a> on <a class="bz_bug_link bz_status_NEEDINFO " title="NEEDINFO - i915 slab shrink cause a panic" href="https://bugs.freedesktop.org/show_bug.cgi?id=109005">bug 109005</a> from <a class="email" href="mailto:bin.yang@intel.com" title="Yang Bin <bin.yang@intel.com>"> Yang Bin</a> <pre>I had reproduced this issue successfully and found the root cause as below. i915_gem_wait_for_idle() waits for all requests being completed and calls i915_retire_requests() to retire them. It assumes the active_requests should be zero finally. In i915_retire_requests(), it will retire all requests on the active rings. Unfortunately, active_requests is increased in i915_request_alloc() and reduced in i915_request_retire(), but the request is added into active rings in i915_request_add(). If i915_gem_wait_for_idle() is called between i915_request_alloc() and i915_request_add(), this request will not be retired. Then, the active_requests will not be zero in the end. 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. I had submitted a RFC patch and continue to discuss it in maillist. Please refer to <a href="https://lkml.org/lkml/2018/12/20/78">https://lkml.org/lkml/2018/12/20/78</a></pre> </div> <hr> You are receiving this mail because: <ul> <li>You are on the CC list for the bug.</li> <li>You are the QA Contact for the bug.</li> <li>You are the assignee for the bug.</li> </ul> </body> </html>