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    Subject[PATCH 4.14 60/62] sched, trace: Fix prev_state output in sched_switch tracepoint
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Pavankumar Kondeti <pkondeti@codeaurora.org>

    commit 3054426dc68e5d63aa6a6e9b91ac4ec78e3f3805 upstream.

    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>
    Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    include/trace/events/sched.h | 12 +++++++++++-
    1 file changed, 11 insertions(+), 1 deletion(-)

    --- a/include/trace/events/sched.h
    +++ b/include/trace/events/sched.h
    @@ -107,6 +107,8 @@ DEFINE_EVENT(sched_wakeup_template, sche
    #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_
    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 */


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