markers: comment marker_synchronize_unregister() on data dependency

Add document and comments on marker_synchronize_unregister(): it
should be called before freeing resources that the probes depend on.

Based on comments from Lai Jiangshan and Mathieu Desnoyers.

Signed-off-by: Wu Fengguang <[email protected]>
Reviewed-by: Mathieu Desnoyers <[email protected]>
Reviewed-by: Lai Jiangshan <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
2 files changed