On 15/03/22 9:14 pm, Paul Menzel wrote: > Dear Arunpravin, > > > Am 15.03.22 um 16:42 schrieb Arunpravin: > >> On 15/03/22 2:35 pm, Paul Menzel wrote: > >>> Am 15.03.22 um 10:01 schrieb Arunpravin: >>> >>>> On 15/03/22 1:49 pm, Paul Menzel wrote: >>> >>>>> Am 14.03.22 um 20:40 schrieb Arunpravin: >>>>>> handle a situation in the condition order-- == min_order, >>>>>> when order = 0, leading to order = -1, it now won't exit >>>>>> the loop. To avoid this problem, added a order check in >>>>>> the same condition, (i.e) when order is 0, we return >>>>>> -ENOSPC >>>>>> >>>>>> Signed-off-by: Arunpravin <Arunpravin.PaneerSelvam@xxxxxxx> >>>>> >>>>> Please use your full name. >>>> okay >>> >>> You might also configure that in your email program. >> yes > > Not done yet though. ;-) > done in v2 :) >>>>>> --- >>>>>> drivers/gpu/drm/drm_buddy.c | 2 +- >>>>>> 1 file changed, 1 insertion(+), 1 deletion(-) >>>>>> >>>>>> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c >>>>>> index 72f52f293249..5ab66aaf2bbd 100644 >>>>>> --- a/drivers/gpu/drm/drm_buddy.c >>>>>> +++ b/drivers/gpu/drm/drm_buddy.c >>>>> >>>>> In what tree is that file? >>>>> >>>> drm-tip - https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcgit.freedesktop.org%2Fdrm-tip%2Ftree%2F&data=04%7C01%7CArunpravin.PaneerSelvam%40amd.com%7C3610aafe216d421c715c08da069ac1d7%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637829559006306914%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=GM3iXiDQCx%2BM4pD1nmivRFRvkehwTNd2Jtd713cF51g%3D&reserved=0 >>>> drm-misc-next - https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fcgit.freedesktop.org%2Fdrm%2Fdrm-misc%2Ftree%2F&data=04%7C01%7CArunpravin.PaneerSelvam%40amd.com%7C3610aafe216d421c715c08da069ac1d7%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637829559006306914%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=i7pvmDJu310XRX7h3cQ344j5RYHq7fBZ520l%2F%2Br1%2BQU%3D&reserved=0 > > Thank Outlook. Now everybody feels safe. > >>>>>> @@ -685,7 +685,7 @@ int drm_buddy_alloc_blocks(struct drm_buddy *mm, >>>>>> if (!IS_ERR(block)) >>>>>> break; >>>>>> >>>>>> - if (order-- == min_order) { >>>>>> + if (!order || order-- == min_order) { >>>>>> err = -ENOSPC; >>>>>> goto err_free; >>>>>> } >>> >>> Thank you for the hint. So the whole function is: >>> >>> do { >>> order = min(order, (unsigned int)fls(pages) - 1); >>> BUG_ON(order > mm->max_order); >>> BUG_ON(order < min_order); >>> >>> do { >>> if (flags & DRM_BUDDY_RANGE_ALLOCATION) >>> /* Allocate traversing within the range */ >>> block = alloc_range_bias(mm, start, end, order); >>> else >>> /* Allocate from freelist */ >>> block = alloc_from_freelist(mm, order, flags); >>> >>> if (!IS_ERR(block)) >>> break; >>> >>> if (order-- == min_order) { >>> err = -ENOSPC; >>> goto err_free; >>> } >>> } while (1); >>> >>> mark_allocated(block); >>> mm->avail -= drm_buddy_block_size(mm, block); >>> kmemleak_update_trace(block); >>> list_add_tail(&block->link, &allocated); >>> >>> pages -= BIT(order); >>> >>> if (!pages) >>> break; >>> } while (1); >>> >>> Was the BUG_ON triggered for your case? >>> >>> BUG_ON(order < min_order); >> no, this BUG_ON is not triggered for this bug >>> >>> Please give more details. >> >> there is a chance when there is no space to allocate, order value >> decrements and reaches to 0 at one point, here we should exit the loop, >> otherwise, further order value decrements to -1 and do..while loop >> doesn't exit. Hence added a check to exit the loop if order value becomes 0. > > Sorry, I do not see it. How can that be with order ≥ min_order and the > check `order-- == min_order`? Is min_order 0? Please explain that in the > next commit message. > please check v2, yes when min_order is 0, the above said situation may occur.And, since the order is unsigned int, I think it will not trigger the BUG_ON(order < min_order) when order becomes -1. Hence I think we needed a check !order to exit the loop. Regards, Arun > > Kind regards, > > Paul >
