Messages in this thread | | | Subject | Re: [PATCH 2/2] drm: mm always protect change to unused_nodes with unused_lock spinlock | From | Jerome Glisse <> | Date | Mon, 16 Nov 2009 09:31:34 +0100 |
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On Mon, 2009-11-16 at 09:42 +1000, Dave Airlie wrote: > On Sat, Nov 14, 2009 at 5:56 AM, Jerome Glisse <jglisse@redhat.com> wrote: > > unused_nodes modification needs to be protected by unused_lock spinlock. > > Here is an example of an usage where there is no such protection without > > this patch. > > > > Process 1: 1-drm_mm_pre_get(this function modify unused_nodes list) > > 2-spin_lock(spinlock protecting mm struct) > > 3-drm_mm_put_block(this function might modify unused_nodes > > list but doesn't protect modification with unused_lock) > > 4-spin_unlock(spinlock protecting mm struct) > > Process2: 1-drm_mm_pre_get(this function modify unused_nodes list) > > At this point Process1 & Process2 might both be doing modification to > > unused_nodes list. This patch add unused_lock protection into > > drm_mm_put_block to avoid such issue. > > Have we got a bug number or reproducer for this? > > I've cc'ed Thomas and Chris who were last ppl to touch drm_mm.c for some > sort of acks. > > Dave.
No bug, this comes from code review while working on TTM. I think my analysis is correct.
Cheers, Jerome
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