1. 10 May, 2010 1 commit
  2. 09 May, 2010 8 commits
  3. 08 May, 2010 2 commits
  4. 07 May, 2010 3 commits
  5. 06 May, 2010 5 commits
    • Paul E. McKenney's avatar
      sched: correctly place paranioa memory barriers in synchronize_sched_expedited() · cc631fb7
      Paul E. McKenney authored
      
      
      The memory barriers must be in the SMP case, not in the !SMP case.
      Also add a barrier after the atomic_inc() in order to ensure that
      other CPUs see post-synchronize_sched_expedited() actions as following
      the expedited grace period.
      Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      cc631fb7
    • Tejun Heo's avatar
      sched: kill paranoia check in synchronize_sched_expedited() · 94458d5e
      Tejun Heo authored
      
      
      The paranoid check which verifies that the cpu_stop callback is
      actually called on all online cpus is completely superflous.  It's
      guaranteed by cpu_stop facility and if it didn't work as advertised
      other things would go horribly wrong and trying to recover using
      synchronize_sched() wouldn't be very meaningful.
      
      Kill the paranoid check.  Removal of this feature is done as a
      separate step so that it can serve as a bisection point if something
      actually goes wrong.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Dipankar Sarma <dipankar@in.ibm.com>
      Cc: Josh Triplett <josh@freedesktop.org>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Dimitri Sivanich <sivanich@sgi.com>
      94458d5e
    • Tejun Heo's avatar
      sched: replace migration_thread with cpu_stop · 969c7921
      Tejun Heo authored
      
      
      Currently migration_thread is serving three purposes - migration
      pusher, context to execute active_load_balance() and forced context
      switcher for expedited RCU synchronize_sched.  All three roles are
      hardcoded into migration_thread() and determining which job is
      scheduled is slightly messy.
      
      This patch kills migration_thread and replaces all three uses with
      cpu_stop.  The three different roles of migration_thread() are
      splitted into three separate cpu_stop callbacks -
      migration_cpu_stop(), active_load_balance_cpu_stop() and
      synchronize_sched_expedited_cpu_stop() - and each use case now simply
      asks cpu_stop to execute the callback as necessary.
      
      synchronize_sched_expedited() was implemented with private
      preallocated resources and custom multi-cpu queueing and waiting
      logic, both of which are provided by cpu_stop.
      synchronize_sched_expedited_count is made atomic and all other shared
      resources along with the mutex are dropped.
      
      synchronize_sched_expedited() also implemented a check to detect cases
      where not all the callback got executed on their assigned cpus and
      fall back to synchronize_sched().  If called with cpu hotplug blocked,
      cpu_stop already guarantees that and the condition cannot happen;
      otherwise, stop_machine() would break.  However, this patch preserves
      the paranoid check using a cpumask to record on which cpus the stopper
      ran so that it can serve as a bisection point if something actually
      goes wrong theree.
      
      Because the internal execution state is no longer visible,
      rcu_expedited_torture_stats() is removed.
      
      This patch also renames cpu_stop threads to from "stopper/%d" to
      "migration/%d".  The names of these threads ultimately don't matter
      and there's no reason to make unnecessary userland visible changes.
      
      With this patch applied, stop_machine() and sched now share the same
      resources.  stop_machine() is faster without wasting any resources and
      sched migration users are much cleaner.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Cc: Ingo Molnar <mingo@elte.hu>
      Cc: Dipankar Sarma <dipankar@in.ibm.com>
      Cc: Josh Triplett <josh@freedesktop.org>
      Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Dimitri Sivanich <sivanich@sgi.com>
      969c7921
    • Tejun Heo's avatar
      stop_machine: reimplement using cpu_stop · 3fc1f1e2
      Tejun Heo authored
      
      
      Reimplement stop_machine using cpu_stop.  As cpu stoppers are
      guaranteed to be available for all online cpus,
      stop_machine_create/destroy() are no longer necessary and removed.
      
      With resource management and synchronization handled by cpu_stop, the
      new implementation is much simpler.  Asking the cpu_stop to execute
      the stop_cpu() state machine on all online cpus with cpu hotplug
      disabled is enough.
      
      stop_machine itself doesn't need to manage any global resources
      anymore, so all per-instance information is rolled into struct
      stop_machine_data and the mutex and all static data variables are
      removed.
      
      The previous implementation created and destroyed RT workqueues as
      necessary which made stop_machine() calls highly expensive on very
      large machines.  According to Dimitri Sivanich, preventing the dynamic
      creation/destruction makes booting faster more than twice on very
      large machines.  cpu_stop resources are preallocated for all online
      cpus and should have the same effect.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Acked-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Dimitri Sivanich <sivanich@sgi.com>
      3fc1f1e2
    • Tejun Heo's avatar
      cpu_stop: implement stop_cpu[s]() · 1142d810
      Tejun Heo authored
      
      
      Implement a simplistic per-cpu maximum priority cpu monopolization
      mechanism.  A non-sleeping callback can be scheduled to run on one or
      multiple cpus with maximum priority monopolozing those cpus.  This is
      primarily to replace and unify RT workqueue usage in stop_machine and
      scheduler migration_thread which currently is serving multiple
      purposes.
      
      Four functions are provided - stop_one_cpu(), stop_one_cpu_nowait(),
      stop_cpus() and try_stop_cpus().
      
      This is to allow clean sharing of resources among stop_cpu and all the
      migration thread users.  One stopper thread per cpu is created which
      is currently named "stopper/CPU".  This will eventually replace the
      migration thread and take on its name.
      
      * This facility was originally named cpuhog and lived in separate
        files but Peter Zijlstra nacked the name and thus got renamed to
        cpu_stop and moved into stop_machine.c.
      
      * Better reporting of preemption leak as per Peter's suggestion.
      Signed-off-by: default avatarTejun Heo <tj@kernel.org>
      Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
      Cc: Oleg Nesterov <oleg@redhat.com>
      Cc: Dimitri Sivanich <sivanich@sgi.com>
      1142d810
  6. 30 Apr, 2010 7 commits
  7. 29 Apr, 2010 10 commits
  8. 28 Apr, 2010 4 commits