• john stultz's avatar
    clockevents: prevent endless loop in tick_handle_periodic() · 74a03b69
    john stultz authored
    tick_handle_periodic() can lock up hard when a one shot clock event
    device is used in combination with jiffies clocksource.
    
    Avoid an endless loop issue by requiring that a highres valid
    clocksource be installed before we call tick_periodic() in a loop when
    using ONESHOT mode. The result is we will only increment jiffies once
    per interrupt until a continuous hardware clocksource is available.
    
    Without this, we can run into a endless loop, where each cycle through
    the loop, jiffies is updated which increments time by tick_period or
    more (due to clock steering), which can cause the event programming to
    think the next event was before the newly incremented time and fail
    causing tick_periodic() to be called again and the whole process loops
    forever.
    
    [ Impact: prevent hard lock up ]
    Signed-off-by: default avatarJohn Stultz <johnstul@us.ibm.com>
    Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    Cc: stable@kernel.org
    74a03b69
tick-common.c 9.39 KB