3.16.80-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Andreas Sandberg <andreas.sandberg@xxxxxxx> commit 38d23a6cc16c02f7b0c920266053f340b5601735 upstream. The hrtimer callback in the hrtimer's tick broadcast code sometimes incorrectly ends up scheduling events at the current tick causing the kernel to hang servicing the same hrtimer forever. This typically happens when a device is swapped out by tick_install_broadcast_device(), which replaces the event handler with clock_events_handle_noop() and sets the device mode to CLOCK_EVT_MODE_UNUSED. If the timer is scheduled when this happens, the next_event field will not be updated and the hrtimer ends up being restarted at the current tick. To prevent this from happening, only try to restart the hrtimer if the broadcast clock event device is in one of the active modes and try to cancel the timer when entering the CLOCK_EVT_MODE_UNUSED mode. Signed-off-by: Andreas Sandberg <andreas.sandberg@xxxxxxx> Tested-by: Catalin Marinas <catalin.marinas@xxxxxxx> Acked-by: Mark Rutland <mark.rutland@xxxxxxx> Reviewed-by: Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx> Link: http://lkml.kernel.org/r/1429880765-5558-1-git-send-email-andreas.sandberg@xxxxxxx Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> [bwh: Backported to 3.16 as dependency of commit b9023b91dd02 "tick: broadcast-hrtimer: Fix a race in bc_set_next"] Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx> --- kernel/time/tick-broadcast-hrtimer.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) --- a/kernel/time/tick-broadcast-hrtimer.c +++ b/kernel/time/tick-broadcast-hrtimer.c @@ -22,6 +22,7 @@ static void bc_set_mode(enum clock_event struct clock_event_device *bc) { switch (mode) { + case CLOCK_EVT_MODE_UNUSED: case CLOCK_EVT_MODE_SHUTDOWN: /* * Note, we cannot cancel the timer here as we might @@ -101,10 +102,13 @@ static enum hrtimer_restart bc_handler(s { ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer); - if (ce_broadcast_hrtimer.next_event.tv64 == KTIME_MAX) + switch (ce_broadcast_hrtimer.mode) { + case CLOCK_EVT_MODE_ONESHOT: + if (ce_broadcast_hrtimer.next_event.tv64 != KTIME_MAX) + return HRTIMER_RESTART; + default: return HRTIMER_NORESTART; - - return HRTIMER_RESTART; + } } void tick_setup_hrtimer_broadcast(void)
