On Thu, Aug 18, 2016 at 9:08 AM, Daniel Vetter <daniel@xxxxxxxx> wrote: > On Thu, Aug 18, 2016 at 06:55:12AM -0400, Rob Clark wrote: >> On Thu, Aug 18, 2016 at 4:36 AM, Daniel Vetter <daniel@xxxxxxxx> wrote: >> > On Wed, Aug 17, 2016 at 05:29:31PM -0400, Rob Clark wrote: >> >> diff --git a/drivers/gpu/drm/msm/msm_gem.c b/drivers/gpu/drm/msm/msm_gem.c >> >> index 6cd4af4..4502e4b 100644 >> >> --- a/drivers/gpu/drm/msm/msm_gem.c >> >> +++ b/drivers/gpu/drm/msm/msm_gem.c >> >> @@ -201,6 +201,13 @@ int msm_gem_fault(struct vm_area_struct *vma, >> >> struct vm_fault *vmf) >> >> pgoff_t pgoff; >> >> int ret; >> >> >> >> + /* I think this should only happen if userspace tries to pass a >> >> + * mmap'd but unfaulted gem bo vaddr into submit ioctl, triggering >> >> + * a page fault while struct_mutex is already held >> >> + */ >> >> + if (mutex_is_locked_by(&dev->struct_mutex, current)) >> >> + return VM_FAULT_SIGBUS; >> > >> > This is an ok (well still horrible) heuristics for the shrinker, but for >> > correctness it kinda doesn't cut it. What you need to do instead is drop >> > all the locks, copy relocations into a temp memory area and then proceed >> > in the msm command submission path above. >> > >> > Also reentrant mutexes are evil ;-) >> >> Please note that this is not a reentrant mutex in the fault path, it >> bails with VM_FAULT_SIGBUG! > > Except on UP it totally deadlocks ;-) except UP does not exist ;-) like I mentioned, I can add 'depends SMP' to kconfig BR, -R > -Daniel > >> There is never a legit reason to use a gem bo for the bos (or cmds) >> table in the ioctl, so while this may not be pretty, I believe it is >> an acceptable solution. > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
