1. 21 Aug, 2009 1 commit
    • Thomas Gleixner's avatar
      x86: Do not unregister PIT clocksource on PIT oneshot setup/shutdown · 8cab02dc
      Thomas Gleixner authored
      This basically reverts commit 1a0c009a (x86: unregister PIT
      clocksource when PIT is disabled) because the problem which was tried
      to address with that patch has been solved by commit 3f68535a
      (clocksource: sanity check sysfs clocksource changes).
      
      The problem addressed by the original patch is that PIT could be
      selected as clocksource after the system switched the PIT off or set
      the PIT into one shot mode which would result in complete timekeeping
      wreckage.
      
      Now with the sysfs sanity check in place PIT cannot be selected again
      when the system is in oneshot mode. The system will not switch to one
      shot mode as long as PIT is installed because PIT is not suitable for
      one shot.
      
      The shutdown case which happens when the lapic timer is installed is
      covered by the fact that init_pit_clocksource() is called after the
      lapic timer take over and then does not install the PIT clocksource
      at all.
      
      We should have done the sanity checks back then, but ...
      
      This also solves the locking problem which was reported vs. the
      clocksource rework.
      
      LKML-Reference: <new-submission>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: john stultz <johnstul@us.ibm.com>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      8cab02dc
  2. 19 Aug, 2009 2 commits
    • Martin Schwidefsky's avatar
      clocksource: Avoid clocksource watchdog circular locking dependency · 01548f4d
      Martin Schwidefsky authored
      stop_machine from a multithreaded workqueue is not allowed because
      of a circular locking dependency between cpu_down and the workqueue
      execution. Use a kernel thread to do the clocksource downgrade.
      Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: john stultz <johnstul@us.ibm.com>
      LKML-Reference: <20090818170942.3ab80c91@skybase>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      01548f4d
    • Thomas Gleixner's avatar
      clocksource: Protect the watchdog rating changes with clocksource_mutex · d0981a1b
      Thomas Gleixner authored
      Martin pointed out that commit 6ea41d2529 (clocksource: Call
      clocksource_change_rating() outside of watchdog_lock) has a
      theoretical reference count problem. The calls to
      clocksource_change_rating() are now done outside of the clocksource
      mutex and outside of the watchdog lock. A concurrent
      clocksource_unregister() could remove the clock.
      
      Split out the code which changes the rating from
      clocksource_change_rating() into __clocksource_change_rating().
      
      Protect the clocksource_watchdog_work() code sequence with the
      clocksource_mutex() and call __clocksource_change_rating().
      
      LKML-Reference: <alpine.LFD.2.00.0908171038420.2782@localhost.localdomain>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
      d0981a1b
  3. 15 Aug, 2009 16 commits
  4. 14 Aug, 2009 1 commit
  5. 13 Aug, 2009 20 commits