This allows to easily trace and visualize priority inheritance
in the binder driver.

Signed-off-by: Martijn Coenen <m...@android.com>
---
 drivers/android/binder.c       |  4 ++++
 drivers/android/binder_trace.h | 24 ++++++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 7768ba280177..9e13711acd14 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -1203,6 +1203,10 @@ static void binder_do_set_priority(struct task_struct 
*task,
                              task->pid, desired.prio,
                              to_kernel_prio(policy, priority));
 
+       trace_binder_set_priority(task->tgid, task->pid, task->normal_prio,
+                                 to_kernel_prio(policy, priority),
+                                 desired.prio);
+
        /* Set the actual priority */
        if (task->policy != policy || is_rt_policy(policy)) {
                struct sched_param params;
diff --git a/drivers/android/binder_trace.h b/drivers/android/binder_trace.h
index 76e3b9c8a8a2..b11dffc521e8 100644
--- a/drivers/android/binder_trace.h
+++ b/drivers/android/binder_trace.h
@@ -85,6 +85,30 @@ DEFINE_BINDER_FUNCTION_RETURN_EVENT(binder_ioctl_done);
 DEFINE_BINDER_FUNCTION_RETURN_EVENT(binder_write_done);
 DEFINE_BINDER_FUNCTION_RETURN_EVENT(binder_read_done);
 
+TRACE_EVENT(binder_set_priority,
+       TP_PROTO(int proc, int thread, unsigned int old_prio,
+                unsigned int desired_prio, unsigned int new_prio),
+       TP_ARGS(proc, thread, old_prio, new_prio, desired_prio),
+
+       TP_STRUCT__entry(
+               __field(int, proc)
+               __field(int, thread)
+               __field(unsigned int, old_prio)
+               __field(unsigned int, new_prio)
+               __field(unsigned int, desired_prio)
+       ),
+       TP_fast_assign(
+               __entry->proc = proc;
+               __entry->thread = thread;
+               __entry->old_prio = old_prio;
+               __entry->new_prio = new_prio;
+               __entry->desired_prio = desired_prio;
+       ),
+       TP_printk("proc=%d thread=%d old=%d => new=%d desired=%d",
+                 __entry->proc, __entry->thread, __entry->old_prio,
+                 __entry->new_prio, __entry->desired_prio)
+);
+
 TRACE_EVENT(binder_wait_for_work,
        TP_PROTO(bool proc_work, bool transaction_stack, bool thread_todo),
        TP_ARGS(proc_work, transaction_stack, thread_todo),
-- 
2.14.1.581.gf28d330327-goog

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