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? Btw, this is the same reason that I dropped the error check at ion_page_pool_shrink, so should I restore here also? Thanks, Tomer Samara _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
