Merge tag 'trace-v4.20-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace

Pull tracing fixes from Steven Rostedt:
 "While rewriting the function graph tracer, I discovered a design flaw
  that was introduced by a patch that tried to fix one bug, but by doing
  so created another bug.

  As both bugs corrupt the output (but they do not crash the kernel), I
  decided to fix the design such that it could have both bugs fixed. The
  original fix, fixed time reporting of the function graph tracer when
  doing a max_depth of one. This was code that can test how much the
  kernel interferes with userspace. But in doing so, it could corrupt
  the time keeping of the function profiler.

  The issue is that the curr_ret_stack variable was being used for two
  different meanings. One was to keep track of the stack pointer on the
  ret_stack (shadow stack used by the function graph tracer), and the
  other use case was the graph call depth. Although, the two may be
  closely related, where they got updated was the issue that lead to the
  two different bugs that required the two use cases to be updated
  differently.

  The big issue with this fix is that it requires changing each
  architecture. The good news is, I was able to remove a lot of code
  that was duplicated within the architectures and place it into a
  single location. Then I could make the fix in one place.

  I pushed this code into linux-next to let it settle over a week, and
  before doing so, I cross compiled all the affected architectures to
  make sure that they built fine.

  In the mean time, I also pulled in a patch that fixes the sched_switch
  previous tasks state output, that was not actually correct"

* tag 'trace-v4.20-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  sched, trace: Fix prev_state output in sched_switch tracepoint
  function_graph: Have profiler use curr_ret_stack and not depth
  function_graph: Reverse the order of pushing the ret_stack and the callback
  function_graph: Move return callback before update of curr_ret_stack
  function_graph: Use new curr_ret_depth to manage depth instead of curr_ret_stack
  function_graph: Make ftrace_push_return_trace() static
  sparc/function_graph: Simplify with function_graph_enter()
  sh/function_graph: Simplify with function_graph_enter()
  s390/function_graph: Simplify with function_graph_enter()
  riscv/function_graph: Simplify with function_graph_enter()
  powerpc/function_graph: Simplify with function_graph_enter()
  parisc: function_graph: Simplify with function_graph_enter()
  nds32: function_graph: Simplify with function_graph_enter()
  MIPS: function_graph: Simplify with function_graph_enter()
  microblaze: function_graph: Simplify with function_graph_enter()
  arm64: function_graph: Simplify with function_graph_enter()
  ARM: function_graph: Simplify with function_graph_enter()
  x86/function_graph: Simplify with function_graph_enter()
  function_graph: Create function_graph_enter() to consolidate architecture code

3 files changed, 14 insertions, 3 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index a397907e8d72..dd16e8218db3 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -777,8 +777,8 @@ struct ftrace_ret_stack {
 extern void return_to_handler(void);
 
 extern int
-ftrace_push_return_trace(unsigned long ret, unsigned long func, int *depth,
-			 unsigned long frame_pointer, unsigned long *retp);
+function_graph_enter(unsigned long ret, unsigned long func,
+		     unsigned long frame_pointer, unsigned long *retp);
 
 unsigned long ftrace_graph_ret_addr(struct task_struct *task, int *idx,
 				    unsigned long ret, unsigned long *retp);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a51c13c2b1a0..d6183a55e8eb 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1116,6 +1116,7 @@ struct task_struct {
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 	/* Index of current stored address in ret_stack: */
 	int				curr_ret_stack;
+	int				curr_ret_depth;
 
 	/* Stack of return addresses for return function tracing: */
 	struct ftrace_ret_stack		*ret_stack;
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index f07b270d4fc4..9a4bdfadab07 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -107,6 +107,8 @@ DEFINE_EVENT(sched_wakeup_template, sched_wakeup_new,
 #ifdef CREATE_TRACE_POINTS
 static inline long __trace_sched_switch_state(bool preempt, struct task_struct *p)
 {
+	unsigned int state;
+
 #ifdef CONFIG_SCHED_DEBUG
 	BUG_ON(p != current);
 #endif /* CONFIG_SCHED_DEBUG */
@@ -118,7 +120,15 @@ static inline long __trace_sched_switch_state(bool preempt, struct task_struct *
 	if (preempt)
 		return TASK_REPORT_MAX;
 
-	return 1 << task_state_index(p);
+	/*
+	 * task_state_index() uses fls() and returns a value from 0-8 range.
+	 * Decrement it by 1 (except TASK_RUNNING state i.e 0) before using
+	 * it for left shift operation to get the correct task->state
+	 * mapping.
+	 */
+	state = task_state_index(p);
+
+	return state ? (1 << (state - 1)) : state;
 }
 #endif /* CREATE_TRACE_POINTS */