Hi Russell, On Thu, 2020-06-11 at 14:01 +0100, Russell King - ARM Linux admin wrote: > On Thu, Jun 11, 2020 at 02:43:31PM +0200, Marco Felsch wrote: > > From: Philipp Zabel <p.zabel@xxxxxxxxxxxxxx> > > > > Component driver structures allocated with devm_kmalloc() in bind() are > > freed automatically after unbind(). Since the contained drm structures > > are accessed afterwards in drm_mode_config_cleanup(), move the > > allocation into probe() to extend the driver structure's lifetime to the > > lifetime of the device. This should eventually be changed to use drm > > resource managed allocations with lifetime of the drm device. > > You need to be extremely careful doing this. If the allocation is > in the probe function, it's lifetime is not just until unbind, but > potentitally to the _next_ bind, unbind, bind, unbind. In other > words, it's lifetime is from the point that the component is probed > to the point that it is later removed. > > If the driver relies on initialisation of that structure, then that > must be _very_ carefully handled - any state in that structure will > remain. > > So, you need to think long and hard about changes like this, and do > a thorough review of the lifetime of every structure member. Thank you for the warning, I've tried to make sure that no driver relies on prior initialization by explicitly replacing each x = devm_kzalloc(dev, sizeof(*x), GFP_KERNEL); in .bind() with a memset(x, 0, sizeof(*x)); The patch still requires the lifetime of embedded connector and encoder structures to end somewhere between .unbind() and the next .bind(), but that should be guaranteed by calling drm_mode_config_cleanup() after component_unbind_all(). I'd like to replace this with devm_drm_dev_alloc() afterwards, but doing this first would allow to fix stable kernels as well. regards Philipp _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
