On 8/22/20 2:34 AM, Tomer Samara wrote: > On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote: >> On 8/21/20 8:28 AM, Tomer Samara wrote: >>> Remove BUG() from ion_sytem_heap.c >>> >>> this fix the following checkpatch issue: >>> Avoid crashing the kernel - try using WARN_ON & >>> recovery code ratherthan BUG() or BUG_ON(). >>> >>> Signed-off-by: Tomer Samara <tomersamara98@xxxxxxxxx> >>> --- >>> drivers/staging/android/ion/ion_system_heap.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c >>> index eac0632ab4e8..00d6154aec34 100644 >>> --- a/drivers/staging/android/ion/ion_system_heap.c >>> +++ b/drivers/staging/android/ion/ion_system_heap.c >>> @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order) >>> for (i = 0; i < NUM_ORDERS; i++) >>> if (order == orders[i]) >>> return i; >>> - BUG(); >>> + /* This is impossible. */ >>> return -1; >>> } >> >> Hi, >> Please explain why this is impossible. >> >> If some caller calls order_to_index(5), it will return -1, yes? >> >> -- >> ~Randy >> > > As Dan Carpenter says here https://lkml.kernel.org/lkml/cover.1597865771.git.tomersamara98@xxxxxxxxx/T/#mc790b91029565b1bb0cb87997b39007d9edb6e04. > After looking at callers we see that order_to_index called from 2 functions: > - alloc_buffer_page called from alloc_largest_available which > loop over all legit order nubmers > ( Flow: > alloc_largest_available-->alloc_buffer_page-->order_to_index > ) > > - free_buffer_page takes the order using compound_order, which return 0 or > the order number for the page, this function has 2 callers too, > ion_system_heap_allocate (which called it in case of failure at sg_alloc_table, > thus calling from this flow will no casue error) and ion_system_heap_free > (which will be called on every sg table in the buffer that allocated good, > meaning from this flow also error will not be created). > ( Flows: > ion_system_heap_free --> free_buffer_page --> order_to_index > ion_system_heap_allocate --> free_buffer_page --> order_to_index > ) > > Of course if some user will use this function with wrong order number he will be able to get this -1. > So should I remove this comment and resotre the error checks? I think so, but that's just an opinion. > Btw, this is the same reason that I dropped the error check at ion_page_pool_shrink, so should I restore here also? IMO yes. Getting rid of BUG()s is a good goal, but usually it's not so easy. thanks. -- ~Randy _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
