On 07/12/2023 08:56, Boris Brezillon wrote: > On Thu, 7 Dec 2023 09:12:43 +0100 > Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> wrote: > >> On Wed, 6 Dec 2023 16:55:42 +0000 >> Steven Price <steven.price@xxxxxxx> wrote: >> >>> On 04/12/2023 17:32, Boris Brezillon wrote: >>>> The panthor driver is designed in a modular way, where each logical >>>> block is dealing with a specific HW-block or software feature. In order >>>> for those blocks to communicate with each other, we need a central >>>> panthor_device collecting all the blocks, and exposing some common >>>> features, like interrupt handling, power management, reset, ... >>>> >>>> This what this panthor_device logical block is about. >>>> >>>> v3: >>>> - Add acks for the MIT+GPL2 relicensing >>>> - Fix 32-bit support >>>> - Shorten the sections protected by panthor_device::pm::mmio_lock to fix >>>> lock ordering issues. >>>> - Rename panthor_device::pm::lock into panthor_device::pm::mmio_lock to >>>> better reflect what this lock is protecting >>>> - Use dev_err_probe() >>>> - Make sure we call drm_dev_exit() when something fails half-way in >>>> panthor_device_reset_work() >>>> - Replace CSF_GPU_LATEST_FLUSH_ID_DEFAULT with a constant '1' and a >>>> comment to explain. Also remove setting the dummy flush ID on suspend. >>>> - Remove drm_WARN_ON() in panthor_exception_name() >>>> - Check pirq->suspended in panthor_xxx_irq_raw_handler() >>>> >>>> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> >>>> Signed-off-by: Steven Price <steven.price@xxxxxxx> >>>> Acked-by: Steven Price <steven.price@xxxxxxx> # MIT+GPL2 relicensing,Arm >>>> Acked-by: Grant Likely <grant.likely@xxxxxxxxxx> # MIT+GPL2 relicensing,Linaro >>>> Acked-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx> # MIT+GPL2 relicensing,Collabora >>> >>> We still have the "FIXME: this is racy" >> >> Yeah, I still didn't find a proper solution for that. > > This [1] should fix the race condition in the unplug path. > > [1]https://gitlab.freedesktop.org/panfrost/linux/-/commit/b79b28069e524ae7fea22a9a158b870eab2d5f9a Looks like it should do the job. I'm surprised that we're the only ones to face this though. Looking at the new imagination driver it appears there's a similar problem: pvr_device_lost() uses a boolean 'lost' to track multiple calls but that boolean isn't protected by any specific lock (AFAICT). Indeed pvr_device_lost() calls drm_dev_unplug() while in a drm_dev_enter() critical section (see pvr_mmu_flush_exec()). If I'm not mistaken that's the same problem we discussed and isn't allowed? drm_dev_unplug() will synchronise on the SRCU that drm_dev_enter() is holding. +CC: Frank, Donald, Matt from Imagination. Steve
