[PATCH] dma-buf: fence debugging

Russell King
2017-03-31T10:00:47Z

Add debugfs output to report shared and exclusive fences on a dma_buf
object. This produces output such as:

Dma-buf Objects:
size flags mode count exp_name
08294400 00000000 00000005 00000005 drm
Exclusive fence: etnaviv 134000.gpu signalled
Attached Devices:
gpu-subsystem
Total 1 devices attached

Total 1 objects, 8294400 bytes

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
---
drivers/dma-buf/dma-buf.c | 34 +++++++++++++++++++++++++++++++++-
1 file changed, 33 insertions(+), 1 deletions(-)

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 0007b792827b..f72aaacbe023 100644
--- a/drivers/dma-buf/dma-buf.c
+++ b/drivers/dma-buf/dma-buf.c
@@ -1059,7 +1059,11 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
int ret;
struct dma_buf *buf_obj;
struct dma_buf_attachment *attach_obj;
- int count = 0, attach_count;
+ struct reservation_object *robj;
+ struct reservation_object_list *fobj;
+ struct dma_fence *fence;
+ unsigned seq;
+ int count = 0, attach_count, shared_count, i;
size_t size = 0;

ret = mutex_lock_interruptible(&db_list.lock);
@@ -1085,6 +1090,34 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
file_count(buf_obj->file),
buf_obj->exp_name);

+ robj = buf_obj->resv;
+ while (true) {
+ seq = read_seqcount_begin(&robj->seq);
+ rcu_read_lock();
+ fobj = rcu_dereference(robj->fence);
+ shared_count = fobj ? fobj->shared_count : 0;
+ fence = rcu_dereference(robj->fence_excl);
+ if (!read_seqcount_retry(&robj->seq, seq))
+ break;
+ rcu_read_unlock();
+ }
+
+ if (fence)
+ seq_printf(s, "\tExclusive fence: %s %s %ssignalled\n",
+ fence->ops->get_driver_name(fence),
+ fence->ops->get_timeline_name(fence),
+ dma_fence_is_signaled(fence) ? "" : "un");
+ for (i = 0; i < shared_count; i++) {
+ fence = rcu_dereference(fobj->shared[i]);
+ if (!dma_fence_get_rcu(fence))
+ continue;
+ seq_printf(s, "\tShared fence: %s %s %ssignalled\n",
+ fence->ops->get_driver_name(fence),
+ fence->ops->get_timeline_name(fence),
+ dma_fence_is_signaled(fence) ? "" : "un");
+ }
+ rcu_read_unlock();
+
seq_puts(s, "\tAttached Devices:\n");
attach_count = 0;

--
2.7.4