Messages in this thread | | | Date | Mon, 16 Nov 2009 09:42:08 +1000 | Subject | Re: [PATCH 2/2] drm: mm always protect change to unused_nodes with unused_lock spinlock | From | Dave Airlie <> |
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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.
> > Signed-off-by: Jerome Glisse <jglisse@redhat.com> > --- > drivers/gpu/drm/drm_mm.c | 9 +++++++++ > 1 files changed, 9 insertions(+), 0 deletions(-) > > diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c > index c861d80..97dc5a4 100644 > --- a/drivers/gpu/drm/drm_mm.c > +++ b/drivers/gpu/drm/drm_mm.c > @@ -103,6 +103,11 @@ static struct drm_mm_node *drm_mm_kmalloc(struct drm_mm *mm, int atomic) > return child; > } > > +/* drm_mm_pre_get() - pre allocate drm_mm_node structure > + * drm_mm: memory manager struct we are pre-allocating for > + * > + * Returns 0 on success or -ENOMEM if allocation fails. > + */ > int drm_mm_pre_get(struct drm_mm *mm) > { > struct drm_mm_node *node; > @@ -253,12 +258,14 @@ void drm_mm_put_block(struct drm_mm_node *cur) > prev_node->size += next_node->size; > list_del(&next_node->ml_entry); > list_del(&next_node->fl_entry); > + spin_lock(&mm->unused_lock); > if (mm->num_unused < MM_UNUSED_TARGET) { > list_add(&next_node->fl_entry, > &mm->unused_nodes); > ++mm->num_unused; > } else > kfree(next_node); > + spin_unlock(&mm->unused_lock); > } else { > next_node->size += cur->size; > next_node->start = cur->start; > @@ -271,11 +278,13 @@ void drm_mm_put_block(struct drm_mm_node *cur) > list_add(&cur->fl_entry, &mm->fl_entry); > } else { > list_del(&cur->ml_entry); > + spin_lock(&mm->unused_lock); > if (mm->num_unused < MM_UNUSED_TARGET) { > list_add(&cur->fl_entry, &mm->unused_nodes); > ++mm->num_unused; > } else > kfree(cur); > + spin_unlock(&mm->unused_lock); > } > } > > -- > 1.6.5.2 > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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