android-mainline/NOUPSTREAM-ANDROID-trace-sched-add-sched-blocked-tracepoint-which-dumps-out-context-of-sleep.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Riley Andrews <riandrews@google.com>
Date: Fri, 2 Oct 2015 00:39:53 -0700
Subject: NOUPSTREAM: ANDROID: trace: sched: add sched blocked tracepoint which
 dumps out context of sleep.

Declare war on uninterruptible sleep. Add a tracepoint which
walks the kernel stack and dumps the first non-scheduler function
called before the scheduler is invoked.

[CPNOTE: 30/06/21] Lee: TODO: Investigate worthiness of upstreaming
[CPNOTE: 30/09/21] Lee: Peter Zijlstra has said 'no more trace events'

Squash:
  ANDROID: sched: move blocked reason trace point to cover all class

Bug: 120445457
Bug: 203080186
Change-Id: I19e965d5206329360a92cbfe2afcc8c30f65c229
Signed-off-by: Riley Andrews <riandrews@google.com>
[astrachan: deleted an unnecessary whitespace change]
Signed-off-by: Alistair Strachan <astrachan@google.com>
Bug: 170916884
Signed-off-by: Todd Kjos <tkjos@google.com>
---
 include/trace/events/sched.h | 24 ++++++++++++++++++++++++
 kernel/sched/core.c          |  3 +++
 2 files changed, 27 insertions(+)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -484,6 +484,30 @@ DEFINE_EVENT_SCHEDSTAT(sched_stat_template, sched_stat_blocked,
 	     TP_PROTO(struct task_struct *tsk, u64 delay),
 	     TP_ARGS(tsk, delay));
 
+/*
+ * Tracepoint for recording the cause of uninterruptible sleep.
+ */
+TRACE_EVENT(sched_blocked_reason,
+
+	TP_PROTO(struct task_struct *tsk),
+
+	TP_ARGS(tsk),
+
+	TP_STRUCT__entry(
+		__field( pid_t,	pid	)
+		__field( void*, caller	)
+		__field( bool, io_wait	)
+	),
+
+	TP_fast_assign(
+		__entry->pid	= tsk->pid;
+		__entry->caller = (void *)get_wchan(tsk);
+		__entry->io_wait = tsk->in_iowait;
+	),
+
+	TP_printk("pid=%d iowait=%d caller=%pS", __entry->pid, __entry->io_wait, __entry->caller)
+);
+
 /*
  * Tracepoint for accounting runtime (time the task is executing
  * on a CPU).
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4033,6 +4033,9 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 	if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags))
 		goto unlock;
 
+	if (READ_ONCE(p->__state) & TASK_UNINTERRUPTIBLE)
+		trace_sched_blocked_reason(p);
+
 #ifdef CONFIG_SMP
 	/*
 	 * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be