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    lockup_detector: Combine nmi_watchdog and softlockup detector · 58687acb
    Don Zickus authored
    
    
    The new nmi_watchdog (which uses the perf event subsystem) is very
    similar in structure to the softlockup detector.  Using Ingo's
    suggestion, I combined the two functionalities into one file:
    kernel/watchdog.c.
    
    Now both the nmi_watchdog (or hardlockup detector) and softlockup
    detector sit on top of the perf event subsystem, which is run every
    60 seconds or so to see if there are any lockups.
    
    To detect hardlockups, cpus not responding to interrupts, I
    implemented an hrtimer that runs 5 times for every perf event
    overflow event.  If that stops counting on a cpu, then the cpu is
    most likely in trouble.
    
    To detect softlockups, tasks not yielding to the scheduler, I used the
    previous kthread idea that now gets kicked every time the hrtimer fires.
    If the kthread isn't being scheduled neither is anyone else and the
    warning is printed to the console.
    
    I tested this on x86_64 and both the softlockup and hardlockup paths
    work.
    
    V2:
    - cleaned up the Kconfig and softlockup combination
    - surrounded hardlockup cases with #ifdef CONFIG_PERF_EVENTS_NMI
    - seperated out the softlockup case from perf event subsystem
    - re-arranged the enabling/disabling nmi watchdog from proc space
    - added cpumasks for hardlockup failure cases
    - removed fallback to soft events if no PMU exists for hard events
    
    V3:
    - comment cleanups
    - drop support for older softlockup code
    - per_cpu cleanups
    - completely remove software clock base hardlockup detector
    - use per_cpu masking on hard/soft lockup detection
    - #ifdef cleanups
    - rename config option NMI_WATCHDOG to LOCKUP_DETECTOR
    - documentation additions
    
    V4:
    - documentation fixes
    - convert per_cpu to __get_cpu_var
    - powerpc compile fixes
    
    V5:
    - split apart warn flags for hard and soft lockups
    
    TODO:
    - figure out how to make an arch-agnostic clock2cycles call
      (if possible) to feed into perf events as a sample period
    
    [fweisbec: merged conflict patch]
    
    Signed-off-by: default avatarDon Zickus <dzickus@redhat.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Cyrill Gorcunov <gorcunov@gmail.com>
    Cc: Eric Paris <eparis@redhat.com>
    Cc: Randy Dunlap <randy.dunlap@oracle.com>
    LKML-Reference: <1273266711-18706-2-git-send-email-dzickus@redhat.com>
    Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
    58687acb