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    Subject[tip:timers/urgent] tick: Fix oneshot broadcast setup really
    Commit-ID:  b435092f70ec5ebbfb6d075d5bf3c631b49a51de
    Gitweb: http://git.kernel.org/tip/b435092f70ec5ebbfb6d075d5bf3c631b49a51de
    Author: Thomas Gleixner <tglx@linutronix.de>
    AuthorDate: Wed, 18 Apr 2012 12:08:23 +0200
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Wed, 18 Apr 2012 14:00:56 +0200

    tick: Fix oneshot broadcast setup really

    Sven Joachim reported, that suspend/resume on rc3 trips over a NULL
    pointer dereference. Linus spotted the clockevent handler being NULL.

    commit fa4da365b(clockevents: tTack broadcast device mode change in
    tick_broadcast_switch_to_oneshot()) tried to fix a problem with the
    broadcast device setup, which was introduced in commit 77b0d60c5(
    clockevents: Leave the broadcast device in shutdown mode when not
    needed).

    The initial commit avoided to set up the broadcast device when no
    broadcast request bits were set, but that left the broadcast device
    disfunctional. In consequence deep idle states which need the
    broadcast device were not woken up.

    commit fa4da365b tried to fix that by initializing the state of the
    broadcast facility, but that missed the fact, that nothing initializes
    the event handler and some other state of the underlying clock event
    device.

    The fix is to revert both commits and make only the mode setting of
    the clock event device conditional on the state of active broadcast
    users.

    That initializes everything except the low level device mode, but this
    happens when the broadcast functionality is invoked by deep idle.

    Reported-and-tested-by: Sven Joachim <svenjoac@gmx.de>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Rafael J. Wysocki <rjw@sisk.pl>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Suresh Siddha <suresh.b.siddha@intel.com>
    Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1204181205540.2542@ionos

    ---
    kernel/time/tick-broadcast.c | 7 +------
    1 files changed, 1 insertions(+), 6 deletions(-)

    diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
    index bf57abd..119aca5 100644
    --- a/kernel/time/tick-broadcast.c
    +++ b/kernel/time/tick-broadcast.c
    @@ -531,7 +531,6 @@ void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
    int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;

    bc->event_handler = tick_handle_oneshot_broadcast;
    - clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);

    /* Take the do_timer update */
    tick_do_timer_cpu = cpu;
    @@ -549,6 +548,7 @@ void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
    to_cpumask(tmpmask));

    if (was_periodic && !cpumask_empty(to_cpumask(tmpmask))) {
    + clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
    tick_broadcast_init_next_event(to_cpumask(tmpmask),
    tick_next_period);
    tick_broadcast_set_event(tick_next_period, 1);
    @@ -577,15 +577,10 @@ void tick_broadcast_switch_to_oneshot(void)
    raw_spin_lock_irqsave(&tick_broadcast_lock, flags);

    tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
    -
    - if (cpumask_empty(tick_get_broadcast_mask()))
    - goto end;
    -
    bc = tick_broadcast_device.evtdev;
    if (bc)
    tick_broadcast_setup_oneshot(bc);

    -end:
    raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
    }

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