From a698cf34ea867efef12fc29dd63d443f0c71a53c Mon Sep 17 00:00:00 2001 From: Jerome Glisse Date: Fri, 13 Nov 2009 20:56:58 +0100 Subject: drm: mm always protect change to unused_nodes with unused_lock spinlock 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. Signed-off-by: Jerome Glisse Signed-off-by: Dave Airlie --- drivers/gpu/drm/drm_mm.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c index c861d80fd77..97dc5a4f0de 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); } } -- cgit v1.2.3