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Commit e1e5fa73 authored by Pavankumar Kondeti's avatar Pavankumar Kondeti Committed by Greg Kroah-Hartman
Browse files

sched, trace: Fix prev_state output in sched_switch tracepoint 

commit 3054426dc68e5d63aa6a6e9b91ac4ec78e3f3805 upstream.

commit 3f5fe9fef5b2 ("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: 3f5fe9fef5b2 ("sched/debug: Fix task state recording/printout")
Signed-off-by: default avatarPavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: default avatarSudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 36c495e9

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 << __get_task_state(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 = __get_task_state(p);



	return state ? (1 << (state - 1)) : state;

}

#endif /* CREATE_TRACE_POINTS */