Commit 3054426d authored Oct 30, 2018 by Pavankumar Kondeti Committed by Steven Rostedt (VMware) Nov 27, 2018

sched, trace: Fix prev_state output in sched_switch tracepoint

commit 3f5fe9fe ("sched/debug: Fix task state recording/printout")
tried to fix the problem introduced by a previous commit efb40f58
("sched/tracing: Fix trace_sched_switch task-state printing"). However
the prev_state output in sched_switch is still broken.

task_state_index() uses fls() which considers the LSB as 1. Left
shifting 1 by this value gives an incorrect mapping to the task state.
Fix this by decrementing the value returned by __get_task_state()
before shifting.

Link: http://lkml.kernel.org/r/1540882473-1103-1-git-send-email-pkondeti@codeaurora.org



Cc: stable@vger.kernel.org
Fixes: 3f5fe9fe ("sched/debug: Fix task state recording/printout")
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

parent b1b35f2e

include/trace/events/sched.h

+11 −1

Original line number	Diff line number	Diff line
		@@ -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 */

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