1. 27 Jun, 2016 3 commits
    • Peter Zijlstra's avatar
      sched/fair: Fix calc_cfs_shares() fixed point arithmetics width confusion · ea1dc6fc
      Peter Zijlstra authored
      Commit:
      
        fde7d22e ("sched/fair: Fix overly small weight for interactive group entities")
      
      did something non-obvious but also did it buggy yet latent.
      
      The problem was exposed for real by a later commit in the v4.7 merge window:
      
        2159197d ("sched/core: Enable increased load resolution on 64-bit kernels")
      
      ... after which tg->load_avg and cfs_rq->load.weight had different
      units (10 bit fixed point and 20 bit fixed point resp.).
      
      Add a comment to explain the use of cfs_rq->load.weight over the
      'natural' cfs_rq->avg.load_avg and add scale_load_down() to correct
      for the difference in unit.
      
      Since this is (now, as per a previous commit) the only user of
      calc_tg_weight(), collapse it.
      
      The effects of this bug should be randomly inconsistent SMP-balancing
      of cgroups workloads.
      Reported-by: default avatarJirka Hladky <jhladky@redhat.com>
      Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Fixes: 2159197d ("sched/core: Enable increased load resolution on 64-bit kernels")
      Fixes: fde7d22e ("sched/fair: Fix overly small weight for interactive group entities")
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      ea1dc6fc
    • Peter Zijlstra's avatar
      sched/fair: Fix effective_load() to consistently use smoothed load · 7dd49125
      Peter Zijlstra authored
      Starting with the following commit:
      
        fde7d22e ("sched/fair: Fix overly small weight for interactive group entities")
      
      calc_tg_weight() doesn't compute the right value as expected by effective_load().
      
      The difference is in the 'correction' term. In order to ensure \Sum
      rw_j >= rw_i we cannot use tg->load_avg directly, since that might be
      lagging a correction on the current cfs_rq->avg.load_avg value.
      Therefore we use tg->load_avg - cfs_rq->tg_load_avg_contrib +
      cfs_rq->avg.load_avg.
      
      Now, per the referenced commit, calc_tg_weight() doesn't use
      cfs_rq->avg.load_avg, as is later used in @w, but uses
      cfs_rq->load.weight instead.
      
      So stop using calc_tg_weight() and do it explicitly.
      
      The effects of this bug are wake_affine() making randomly
      poor choices in cgroup-intense workloads.
      Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Cc: <stable@vger.kernel.org> # v4.3+
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Fixes: fde7d22e ("sched/fair: Fix overly small weight for interactive group entities")
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      7dd49125
    • Linus Torvalds's avatar
      Linux 4.7-rc5 · 4c2e07c6
      Linus Torvalds authored
      4c2e07c6
  2. 26 Jun, 2016 1 commit
    • Linus Torvalds's avatar
      Merge tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi · 2ac9b973
      Linus Torvalds authored
      Pull SCSI fixes from James Bottomley:
       "Two straightforward fixes.
      
        One is a concurrency issue only affecting SAS connected SATA drives,
        but which could hang the storage subsystem if it triggers (because the
        outstanding command count on error never goes back to zero) and the
        other is a NO_TAG fallout from the switch to hostwide tags which
        causes the system to crash on module insertion (we've checked
        carefully and only the 53c700 family of drivers is vulnerable to this
        issue)"
      
      * tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
        53c700: fix BUG on untagged commands
        scsi: fix race between simultaneous decrements of ->host_failed
      2ac9b973
  3. 25 Jun, 2016 36 commits