On Fri, Dec 30, 2022 at 12:03:25PM +0200, Mikko Perttunen wrote: > On 12/30/22 12:01, Mikko Perttunen wrote: > > On 12/30/22 11:15, Stanislaw Gruszka wrote: > > > On Wed, Dec 28, 2022 at 03:17:59PM +0200, Mikko Perttunen wrote: > > > > On 12/28/22 15:08, Deepak R Varma wrote: > > > > > On Wed, Dec 28, 2022 at 02:28:54PM +0200, Mikko Perttunen wrote: > > > > > > On 12/27/22 19:14, Deepak R Varma wrote: > > > > > > > kfree() & vfree() internally perform NULL check on the pointer handed > > > > > > > to it and take no action if it indeed is NULL. Hence there is no need > > > > > > > for a pre-check of the memory pointer before handing it to > > > > > > > kfree()/vfree(). > > > > > > > > > > > > > > Issue reported by ifnullfree.cocci Coccinelle semantic patch script. > > > > > > > > > > > > > > Signed-off-by: Deepak R Varma <drv@xxxxxxxxx> > > > > > > > --- > > > > > > > drivers/gpu/drm/tegra/submit.c | 4 ++-- > > > > > > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > > > > > > > > > > > diff --git a/drivers/gpu/drm/tegra/submit.c > > > > > > > b/drivers/gpu/drm/tegra/submit.c > > > > > > > index 066f88564169..06f836db99d0 100644 > > > > > > > --- a/drivers/gpu/drm/tegra/submit.c > > > > > > > +++ b/drivers/gpu/drm/tegra/submit.c > > > > > > > @@ -680,8 +680,8 @@ int > > > > > > > tegra_drm_ioctl_channel_submit(struct drm_device > > > > > > > *drm, void *data, > > > > > > > kfree(job_data->used_mappings); > > > > > > > } > > > > > > > > > > > > > > - if (job_data) > > > > > > > - kfree(job_data); > > > > > > > + kfree(job_data); > > > > > > > + > > > > > > > put_bo: > > > > > > > gather_bo_put(&bo->base); > > > > > > > unlock: > > > > > > > -- > > > > > > > 2.34.1 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > It continues to be the case that I think this transform > > > > > > is bad. Same applies > > > > > > to the host1x patch. > > > > > > > > > > Hello Mikko, > > > > > Thank you for responding to the patch proposal. Could you > > > > > please explain why is > > > > > this bad? > > > > > > > > > > Regards, > > > > > ./drv > > > > > > > > > > > > > > > > > Mikko > > > > > > > > > > > > > > > > > > Hi, > > > > > > > > it gets rid of visual hints on code paths indicating the > > > > possible liveness > > > > of pointer variables. I.e., after the change, whether the pointer can be > > > > NULL or not is more difficult to reason about locally, instead requiring > > > > more global reasoning which is mentally more taxing. > > > > > > > > Since C's type system doesn't help with tracking these kinds of > > > > things, I > > > > believe it is important to have these kinds of local contextual > > > > cues to help > > > > the programmer. > > > > > > I agree with your point of view. But regarding this particular patch, > > > at least on code base I can see, after free_job_data label job_done > > > can not be NULL. So patch seems to be ok, but maybe changelog need to > > > be different > > > > > > Regards > > > Stanislaw > > > > It can be NULL; see: > > > > job->user_data = job_data; > > job->release = release_job; > > job->timeout = 10000; > > > > /* > > * job_data is now part of job reference counting, so don't > > release > > * it from here. > > */ > > job_data = NULL; > > > > If we go into free_job_data after this code (which happens if there is > > no error, or if host1x_job_submit fails), job_data will be NULL. > > > > The memory is instead released in the 'put_job' label; host1x_job_put > > ends up calling release_job, which does the kfree. > > Well, the refcount is dropped -- it's not necessarily freed immediately, if > the job is in execution. Thanks Mikko. I Agree. Hence I think there is no change for the program at runtime. The proposed change looks safe to me. ./drv > > Mikko > > > > > (Yes, it is rather complicated..) > > > > Thanks, > > Mikko >
