On Fri, Oct 29, 2021 at 2:48 PM Tadeusz Struk <tadeusz.struk@xxxxxxxxxx> wrote: > > Venus video encode/decode hardware driver consists of three modules. > The parent module venus-core, and two sub modules venus-enc and venus-dec. > The venus-core module allocates a common structure that is used by the > enc/dec modules, loads the firmware, and performs some common hardware > initialization. Since the three modules are loaded one after the other, > and their probe functions can run in parallel it is possible that > the venc_probe and vdec_probe functions can finish before the core > venus_probe function, which then can fail when, for example it > fails to load the firmware. In this case the subsequent call to venc_open > causes an Oops as it tries to dereference already uninitialized structures > through dev->parent and the system crashes in __pm_runtime_resume() as in > the trace below: > > [ 26.064835][ T485] Internal error: Oops: 96000006 [#1] PREEMPT SMP > [ 26.270914][ T485] Hardware name: Thundercomm Dragonboard 845c (DT) > [ 26.285019][ T485] pc : __pm_runtime_resume+0x34/0x178 > [ 26.286374][ T213] lt9611 10-003b: hdmi cable connected > [ 26.290285][ T485] lr : venc_open+0xc0/0x278 [venus_enc] > [ 26.290326][ T485] Call trace: > [ 26.290328][ T485] __pm_runtime_resume+0x34/0x178 > [ 26.290330][ T485] venc_open+0xc0/0x278 [venus_enc] > [ 26.290335][ T485] v4l2_open+0x184/0x294 > [ 26.290340][ T485] chrdev_open+0x468/0x5c8 > [ 26.290344][ T485] do_dentry_open+0x260/0x54c > [ 26.290349][ T485] path_openat+0xbe8/0xd5c > [ 26.290352][ T485] do_filp_open+0xb8/0x168 > [ 26.290354][ T485] do_sys_openat2+0xa4/0x1e8 > [ 26.290357][ T485] __arm64_compat_sys_openat+0x70/0x9c > [ 26.290359][ T485] invoke_syscall+0x60/0x170 > [ 26.290363][ T485] el0_svc_common+0xb8/0xf8 > [ 26.290365][ T485] do_el0_svc_compat+0x20/0x30 > [ 26.290367][ T485] el0_svc_compat+0x24/0x84 > [ 26.290372][ T485] el0t_32_sync_handler+0x7c/0xbc > [ 26.290374][ T485] el0t_32_sync+0x1b8/0x1bc > [ 26.290381][ T485] ---[ end trace 04ca7c088b4c1a9c ]--- > [ 26.290383][ T485] Kernel panic - not syncing: Oops: Fatal exception > > This can be fixed by synchronizing the three probe functions and > only allowing the venc_probe() and vdec_probe() to pass when venus_probe() > returns success. > > Changes in v2: > - Change locking from mutex_lock to mutex_trylock > in venc_probe and vdec_probe to avoid potential deadlock. > > Signed-off-by: Tadeusz Struk <tadeusz.struk@xxxxxxxxxx> Just wanted to ping folks on this patch, as it does resolve a frequent crash that we see on db845c/RB3 and RB5 hardware, so it would be nice to see it land & backported to -stable. thanks -john
