On Fri, 29 Nov 2019 19:40:38 +0100 Daniel Vetter <daniel@xxxxxxxx> wrote: > On Fri, Nov 29, 2019 at 03:19:36PM +0100, Boris Brezillon wrote: > > On Fri, 29 Nov 2019 14:13:33 +0000 > > Steven Price <steven.price@xxxxxxx> wrote: > > > > > On 29/11/2019 13:56, Boris Brezillon wrote: > > > > I've spent hours chasing a memory corruption that was caused by > > > > insertion of an extra field field before ->base. Let's document the > > > > fact that base has to be the first field in panfrost_gem_object. > > > > > > > > Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> > > > > > > This seems to be a limitation imposed by the gem_create_object() > > > callback - e.g. it's assumed that kfree() can be directly called on the > > > result. Useful to have the documentation though. > > > > Oh, you're right, I didn't catch that one. > > As a general rule of thumb, never insert anything before a struct member > called base. Even more so if it's of the same kind of $thing, but less > spezialed. This pattern is so common it's fairly often not documented > anywhere. I could argue that anything using container_of() in its to_xxx() helper is misleading the user into thinking the position of the base field doesn't matter (which is exactly what happened here), but I feel like I already lost this battle, so I'll simply drop the patch. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
