Re: [PATCH] drm: Fix writeback_job leak when state is check only or check failed

[james qian wang (Arm Technology China)]

On Thu, Feb 21, 2019 at 02:56:56PM +0100, Maarten Lankhorst wrote:
> Hey
> 
> Op 21-02-2019 om 12:14 schreef james qian wang (Arm Technology China):
> > The writeback job will not be added to writeback queue if the state is
> > check only or check failed, to avoid leak, need to cleanup writeback job
> > in connector_destroy_state if the job existed.
> >
> > Signed-off-by: James Qian Wang (Arm Technology China) 
> > <james.qian.w...@arm.com>
> 
> Is writeback_job in the conn_state set to null somewhere? I'm worried we 
> might end up freeing writeback_job twice on success.
> 
> ~Maarten

Yes, the state->writeback_job need to be set to null once the job has been
queued.
Maybe we can refine the queue_job function and add this set NULL into
it.

void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
                             struct drm_writeback_job **new_job)
{
        struct drm_writeback_job *job = *new_job;
        unsigned long flags;

        *new_job = NULL;

        spin_lock_irqsave(&wb_connector->job_lock, flags);
        list_add_tail(&job->list_entry, &wb_connector->job_queue);
        spin_unlock_irqrestore(&wb_connector->job_lock, flags);
}

Thanks
James

> 
> >  drivers/gpu/drm/drm_atomic_state_helper.c |  4 ++++
> >  drivers/gpu/drm/drm_writeback.c           | 21 ++++++++++++++++++---
> >  2 files changed, 22 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/drm_atomic_state_helper.c 
> > b/drivers/gpu/drm/drm_atomic_state_helper.c
> > index 4985384e51f6..6a8e414233de 100644
> > --- a/drivers/gpu/drm/drm_atomic_state_helper.c
> > +++ b/drivers/gpu/drm/drm_atomic_state_helper.c
> > @@ -28,6 +28,7 @@
> >  #include <drm/drm_crtc.h>
> >  #include <drm/drm_plane.h>
> >  #include <drm/drm_connector.h>
> > +#include <drm/drm_writeback.h>
> >  #include <drm/drm_atomic.h>
> >  #include <drm/drm_device.h>
> >  
> > @@ -407,6 +408,9 @@ 
> > EXPORT_SYMBOL(drm_atomic_helper_connector_duplicate_state);
> >  void
> >  __drm_atomic_helper_connector_destroy_state(struct drm_connector_state 
> > *state)
> >  {
> > +   if (state->writeback_job)
> > +           drm_writeback_cleanup_job(state->writeback_job);
> > +
> >     if (state->crtc)
> >             drm_connector_put(state->connector);
> >  
> > diff --git a/drivers/gpu/drm/drm_writeback.c 
> > b/drivers/gpu/drm/drm_writeback.c
> > index c20e6fe00cb3..486121150eaa 100644
> > --- a/drivers/gpu/drm/drm_writeback.c
> > +++ b/drivers/gpu/drm/drm_writeback.c
> > @@ -268,6 +268,22 @@ void drm_writeback_queue_job(struct 
> > drm_writeback_connector *wb_connector,
> >  }
> >  EXPORT_SYMBOL(drm_writeback_queue_job);
> >  
> > +/**
> > + * drm_writeback_cleanup_job - cleanup a writeback job
> > + * @job: The job to cleanup
> > + */
> > +void drm_writeback_cleanup_job(struct drm_writeback_job *job)
> > +{
> > +   if (job->fb)
> > +           drm_framebuffer_put(job->fb);
> > +
> > +   if (job->out_fence)
> > +           dma_fence_put(job->out_fence);
> > +
> > +   kfree(job);
> > +}
> > +EXPORT_SYMBOL(drm_writeback_cleanup_job);
> > +
> >  /*
> >   * @cleanup_work: deferred cleanup of a writeback job
> >   *
> > @@ -280,11 +296,9 @@ static void cleanup_work(struct work_struct *work)
> >     struct drm_writeback_job *job = container_of(work,
> >                                                  struct drm_writeback_job,
> >                                                  cleanup_work);
> > -   drm_framebuffer_put(job->fb);
> > -   kfree(job);
> > +   drm_writeback_cleanup_job(job);
> >  }
> >  
> > -
> >  /**
> >   * drm_writeback_signal_completion - Signal the completion of a writeback 
> > job
> >   * @wb_connector: The writeback connector whose job is complete
> > @@ -319,6 +333,7 @@ drm_writeback_signal_completion(struct 
> > drm_writeback_connector *wb_connector,
> >                             dma_fence_set_error(job->out_fence, status);
> >                     dma_fence_signal(job->out_fence);
> >                     dma_fence_put(job->out_fence);
> > +                   job->out_fence = NULL;
> >             }
> >     }
> >     spin_unlock_irqrestore(&wb_connector->job_lock, flags);
> 
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