1. 29 Jan, 2018 17 commits
  2. 28 Jan, 2018 8 commits
  3. 27 Jan, 2018 2 commits
    • Thomas Gleixner's avatar
      hrtimer: Reset hrtimer cpu base proper on CPU hotplug · d5421ea4
      Thomas Gleixner authored
      The hrtimer interrupt code contains a hang detection and mitigation
      mechanism, which prevents that a long delayed hrtimer interrupt causes a
      continous retriggering of interrupts which prevent the system from making
      progress. If a hang is detected then the timer hardware is programmed with
      a certain delay into the future and a flag is set in the hrtimer cpu base
      which prevents newly enqueued timers from reprogramming the timer hardware
      prior to the chosen delay. The subsequent hrtimer interrupt after the delay
      clears the flag and resumes normal operation.
      
      If such a hang happens in the last hrtimer interrupt before a CPU is
      unplugged then the hang_detected flag is set and stays that way when the
      CPU is plugged in again. At that point the timer hardware is not armed and
      it cannot be armed because the hang_detected flag is still active, so
      nothing clears that flag. As a consequence the CPU does not receive hrtimer
      interrupts and no timers expire on that CPU which results in RCU stalls and
      other malfunctions.
      
      Clear the flag along with some other less critical members of the hrtimer
      cpu base to ensure starting from a clean state when a CPU is plugged in.
      
      Thanks to Paul, Sebastian and Anna-Maria for their help to get down to the
      root cause of that hard to reproduce heisenbug. Once understood it's
      trivial and certainly justifies a brown paperbag.
      
      Fixes: 41d2e494 ("hrtimer: Tune hrtimer_interrupt hang logic")
      Reported-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Sebastian Sewior <bigeasy@linutronix.de>
      Cc: Anna-Maria Gleixner <anna-maria@linutronix.de>
      Cc: stable@vger.kernel.org
      Link: https://lkml.kernel.org/r/alpine.DEB.2.20.1801261447590.2067@nanos
      d5421ea4
    • H. Peter Anvin's avatar
      x86: Mark hpa as a "Designated Reviewer" for the time being · 8a95b74d
      H. Peter Anvin authored
      Due to some unfortunate events, I have not been directly involved in
      the x86 kernel patch flow for a while now.  I have also not been able
      to ramp back up by now like I had hoped to, and after reviewing what I
      will need to work on both internally at Intel and elsewhere in the near
      term, it is clear that I am not going to be able to ramp back up until
      late 2018 at the very earliest.
      
      It is not acceptable to not recognize that this load is currently
      taken by Ingo and Thomas without my direct participation, so I mark
      myself as R: (designated reviewer) rather than M: (maintainer) until
      further notice.  This is in fact recognizing the de facto situation
      for the past few years.
      
      I have obviously no intention of going away, and I will do everything
      within my power to improve Linux on x86 and x86 for Linux.  This,
      however, puts credit where it is due and reflects a change of focus.
      
      This patch also removes stale entries for portions of the x86
      architecture which have not been maintained separately from arch/x86
      for a long time.  If there is a reason to re-introduce them then that
      can happen later.
      Signed-off-by: default avatarH. Peter Anvin <h.peter.anvin@intel.com>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: Bruce Schlobohm <bruce.schlobohm@intel.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Link: http://lkml.kernel.org/r/20180125195934.5253-1-hpa@zytor.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
      8a95b74d
  4. 26 Jan, 2018 13 commits