1. 08 Mar, 2016 10 commits
  2. 04 Mar, 2016 1 commit
  3. 25 Feb, 2016 1 commit
  4. 23 Feb, 2016 3 commits
  5. 19 Feb, 2016 2 commits
    • Tejun Heo's avatar
      Revert "workqueue: make sure delayed work run in local cpu" · 61f41b6f
      Tejun Heo authored
      commit 041bd12e upstream.
      
      This reverts commit 874bbfe6.
      
      Workqueue used to implicity guarantee that work items queued without
      explicit CPU specified are put on the local CPU.  Recent changes in
      timer broke the guarantee and led to vmstat breakage which was fixed
      by 176bed1d ("vmstat: explicitly schedule per-cpu work on the CPU
      we need it to run on").
      
      vmstat is the most likely to expose the issue and it's quite possible
      that there are other similar problems which are a lot more difficult
      to trigger.  As a preventive measure, 874bbfe6 ("workqueue: make
      sure delayed work run in local cpu") was applied to restore the local
      CPU guarnatee.  Unfortunately, the change exposed a bug in timer code
      which got fixed by 22b886dd ("timers: Use proper base migration in
      add_timer_on()").  Due to code restructuring, the commit couldn't be
      backported beyond certain point and stable kernels which only had
      874bbfe6 started crashing.
      
      The local CPU guarantee was accidental more than anything else and we
      want to get rid of it anyway.  As, with the vmstat case fixed,
      874bbfe6 is causing more problems than it's fixing, it has been
      decided to take the chance and officially break the guarantee by
      reverting the commit.  A debug feature will be added to force foreign
      CPU assignment to expose cases relying on the guarantee and fixes for
      the individual cases will be backported to stable as necessary.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Fixes: 874bbfe6 ("workqueue: make sure delayed work run in local cpu")
      Link: http://lkml.kernel.org/g/20160120211926.GJ10810@quack.suse.cz
      Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
      Cc: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
      Cc: Daniel Bilik <daniel.bilik@neosystem.cz>
      Cc: Jan Kara <jack@suse.cz>
      Cc: Shaohua Li <shli@fb.com>
      Cc: Sasha Levin <sasha.levin@oracle.com>
      Cc: Ben Hutchings <ben@decadent.org.uk>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: Daniel Bilik <daniel.bilik@neosystem.cz>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Michal Hocko <mhocko@kernel.org>
      Signed-off-by: default avatarKamal Mostafa <kamal@canonical.com>
      61f41b6f
    • Linus Torvalds's avatar
      vmstat: explicitly schedule per-cpu work on the CPU we need it to run on · 32083def
      Linus Torvalds authored
      commit 176bed1d upstream.
      
      The vmstat code uses "schedule_delayed_work_on()" to do the initial
      startup of the delayed work on the right CPU, but then once it was
      started it would use the non-cpu-specific "schedule_delayed_work()" to
      re-schedule it on that CPU.
      
      That just happened to schedule it on the same CPU historically (well, in
      almost all situations), but the code _requires_ this work to be per-cpu,
      and should say so explicitly rather than depend on the non-cpu-specific
      scheduling to schedule on the current CPU.
      
      The timer code is being changed to not be as single-minded in always
      running things on the calling CPU.
      
      See also commit 874bbfe6 ("workqueue: make sure delayed work run in
      local cpu") that for now maintains the local CPU guarantees just in case
      there are other broken users that depended on the accidental behavior.
      
      Cc: Christoph Lameter <cl@linux.com>
      Cc: Tejun Heo <tj@kernel.org>
      Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      [ kamal: backport to 3.19-stable: use queue_delayed_work_on() ]
      Signed-off-by: default avatarKamal Mostafa <kamal@canonical.com>
      32083def
  6. 12 Feb, 2016 2 commits
  7. 11 Feb, 2016 21 commits