• Suresh Siddha's avatar
    clockevent: Prevent dead lock on clockevents_lock · f833bab8
    Suresh Siddha authored
    Currently clockevents_notify() is called with interrupts enabled at
    some places and interrupts disabled at some other places.
    
    This results in a deadlock in this scenario.
    
    cpu A holds clockevents_lock in clockevents_notify() with irqs enabled
    cpu B waits for clockevents_lock in clockevents_notify() with irqs disabled
    cpu C doing set_mtrr() which will try to rendezvous of all the cpus.
    
    This will result in C and A come to the rendezvous point and waiting
    for B. B is stuck forever waiting for the spinlock and thus not
    reaching the rendezvous point.
    
    Fix the clockevents code so that clockevents_lock is taken with
    interrupts disabled and thus avoid the above deadlock.
    
    Also call lapic_timer_propagate_broadcast() on the destination cpu so
    that we avoid calling smp_call_function() in the clockevents notifier
    chain.
    
    This issue left us wondering if we need to change the MTRR rendezvous
    logic to use stop machine logic (instead of smp_call_function) or add
    a check in spinlock debug code to see if there are other spinlocks
    which gets taken under both interrupts enabled/disabled conditions.
    Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
    Signed-off-by: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
    Cc: "Pallipadi Venkatesh" <venkatesh.pallipadi@intel.com>
    Cc: "Brown Len" <len.brown@intel.com>
    LKML-Reference: <1250544899.2709.210.camel@sbs-t61.sc.intel.com>
    Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    f833bab8
process.c 14.2 KB