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sched, trace: Fix prev_state output in sched_switch tracepoint

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commit 3f5fe9fef5b2 ("sched/debug: Fix task state recording/printout")
tried to fix the problem introduced by a previous commit efb40f588b43
("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: Pavankumar Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Pavankumar Kondeti 2018-10-30 12:24:33 +05:30 committed by Steven Rostedt (VMware)
parent b1b35f2e21
commit 3054426dc6
1 changed files with 11 additions and 1 deletions
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12
include/trace/events/sched.h
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@ -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 */