1. 18 May, 2015 1 commit
    • Peter Zijlstra's avatar
      sched,perf: Fix periodic timers · 4cfafd30
      Peter Zijlstra authored
      In the below two commits (see Fixes) we have periodic timers that can
      stop themselves when they're no longer required, but need to be
      (re)-started when their idle condition changes.
      Further complications is that we want the timer handler to always do
      the forward such that it will always correctly deal with the overruns,
      and we do not want to race such that the handler has already decided
      to stop, but the (external) restart sees the timer still active and we
      end up with a 'lost' timer.
      The problem with the current code is that the re-start can come before
      the callback does the forward, at which point the forward from the
      callback will WARN about forwarding an enqueued timer.
      Now, conceptually its easy to detect if you're before or after the fwd
      by comparing the expiration time against the current time. Of course,
      that's expensive (and racy) because we don't have the current time.
      Alternatively one could cache this state inside the timer, but then
      everybody pays the overhead of maintaining this extra state, and that
      is undesired.
      The only other option that I could see is the external timer_active
      variable, which I tried to kill before. I would love a nicer interface
      for this seemingly simple 'problem' but alas.
      Fixes: 272325c4 ("perf: Fix mux_interval hrtimer wreckage")
      Fixes: 77a4d1a1 ("sched: Cleanup bandwidth timers")
      Cc: pjt@google.com
      Cc: tglx@linutronix.de
      Cc: klamm@yandex-team.ru
      Cc: mingo@kernel.org
      Cc: bsegall@google.com
      Cc: hpa@zytor.com
      Cc: Sasha Levin <sasha.levin@oracle.com>
      Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Link: http://lkml.kernel.org/r/20150514102311.GX21418@twins.programming.kicks-ass.net
  2. 12 May, 2015 1 commit
  3. 07 May, 2015 1 commit
  4. 05 May, 2015 8 commits
  5. 04 May, 2015 1 commit
  6. 23 Apr, 2015 2 commits
  7. 22 Apr, 2015 26 commits