linux-toradex.git/kernel/sched, branch v3.19-rc2

sched_show_task: fix unsafe usage of ->real_parent

2014-12-11T01:41:09+00:00

rcu_read_lock() can not protect p->real_parent if release_task(p) was
already called, change sched_show_task() to check pis_alive() like other
users do.

Note: we need some helpers to cleanup the code like this.  And it seems
that that the usage of cpu_curr(cpu) in dump_cpu_task() is not safe too.

Signed-off-by: Oleg Nesterov 
Cc: Aaron Tomlin 
Cc: Alexey Dobriyan 
Cc: "Eric W. Biederman" ,
Cc: Sterling Alexander 
Acked-by: Peter Zijlstra (Intel) 
Cc: Roland McGrath 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2014-12-10T05:21:34+00:00

Pull scheduler updates from Ingo Molnar:
 "The main changes in this cycle are:

   - 'Nested Sleep Debugging', activated when CONFIG_DEBUG_ATOMIC_SLEEP=y.

     This instruments might_sleep() checks to catch places that nest
     blocking primitives - such as mutex usage in a wait loop.  Such
     bugs can result in hard to debug races/hangs.

     Another category of invalid nesting that this facility will detect
     is the calling of blocking functions from within schedule() ->
     sched_submit_work() -> blk_schedule_flush_plug().

     There's some potential for false positives (if secondary blocking
     primitives themselves are not ready yet for this facility), but the
     kernel will warn once about such bugs per bootup, so the warning
     isn't much of a nuisance.

     This feature comes with a number of fixes, for problems uncovered
     with it, so no messages are expected normally.

   - Another round of sched/numa optimizations and refinements, for
     CONFIG_NUMA_BALANCING=y.

   - Another round of sched/dl fixes and refinements.

  Plus various smaller fixes and cleanups"

* 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
  sched: Add missing rcu protection to wake_up_all_idle_cpus
  sched/deadline: Introduce start_hrtick_dl() for !CONFIG_SCHED_HRTICK
  sched/numa: Init numa balancing fields of init_task
  sched/deadline: Remove unnecessary definitions in cpudeadline.h
  sched/cpupri: Remove unnecessary definitions in cpupri.h
  sched/deadline: Fix rq->dl.pushable_tasks bug in push_dl_task()
  sched/fair: Fix stale overloaded status in the busiest group finding logic
  sched: Move p->nr_cpus_allowed check to select_task_rq()
  sched/completion: Document when to use wait_for_completion_io_*()
  sched: Update comments about CLONE_NEWUTS and CLONE_NEWIPC
  sched/fair: Kill task_struct::numa_entry and numa_group::task_list
  sched: Refactor task_struct to use numa_faults instead of numa_* pointers
  sched/deadline: Don't check CONFIG_SMP in switched_from_dl()
  sched/deadline: Reschedule from switched_from_dl() after a successful pull
  sched/deadline: Push task away if the deadline is equal to curr during wakeup
  sched/deadline: Add deadline rq status print
  sched/deadline: Fix artificial overrun introduced by yield_task_dl()
  sched/rt: Clean up check_preempt_equal_prio()
  sched/core: Use dl_bw_of() under rcu_read_lock_sched()
  sched: Check if we got a shallowest_idle_cpu before searching for least_loaded_cpu
  ...

Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2014-12-10T04:23:19+00:00

Pull RCU updates from Ingo Molnar:
 "These are the main changes in this cycle:

    - Streamline RCU's use of per-CPU variables, shifting from "cpu"
      arguments to functions to "this_"-style per-CPU variable
      accessors.

    - signal-handling RCU updates.

    - real-time updates.

    - torture-test updates.

    - miscellaneous fixes.

    - documentation updates"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (34 commits)
  rcu: Fix FIXME in rcu_tasks_kthread()
  rcu: More info about potential deadlocks with rcu_read_unlock()
  rcu: Optimize cond_resched_rcu_qs()
  rcu: Add sparse check for RCU_INIT_POINTER()
  documentation: memory-barriers.txt: Correct example for reorderings
  documentation: Add atomic_long_t to atomic_ops.txt
  documentation: Additional restriction for control dependencies
  documentation: Document RCU self test boot params
  rcutorture: Fix rcu_torture_cbflood() memory leak
  rcutorture: Remove obsolete kversion param in kvm.sh
  rcutorture: Remove stale test configurations
  rcutorture: Enable RCU self test in configs
  rcutorture: Add early boot self tests
  torture: Run Linux-kernel binary out of results directory
  cpu: Avoid puts_pending overflow
  rcu: Remove "cpu" argument to rcu_cleanup_after_idle()
  rcu: Remove "cpu" argument to rcu_prepare_for_idle()
  rcu: Remove "cpu" argument to rcu_needs_cpu()
  rcu: Remove "cpu" argument to rcu_note_context_switch()
  rcu: Remove "cpu" argument to rcu_preempt_check_callbacks()
  ...

sched: Add missing rcu protection to wake_up_all_idle_cpus

2014-12-08T10:44:19+00:00

Locklessly doing is_idle_task(rq->curr) is only okay because of
RCU protection.  The older variant of the broken code checked
rq->curr == rq->idle instead and therefore didn't need RCU.

Fixes: f6be8af1c95d ("sched: Add new API wake_up_if_idle() to wake up the idle cpu")
Signed-off-by: Andy Lutomirski 
Reviewed-by: Chuansheng Liu 
Cc: Peter Zijlstra 
Link: http://lkml.kernel.org/r/729365dddca178506dfd0a9451006344cd6808bc.1417277372.git.luto@amacapital.net
Signed-off-by: Ingo Molnar

context_tracking: Restore previous state in schedule_user

2014-12-04T04:55:58+00:00

It appears that some SCHEDULE_USER (asm for schedule_user) callers
in arch/x86/kernel/entry_64.S are called from RCU kernel context,
and schedule_user will return in RCU user context.  This causes RCU
warnings and possible failures.

This is intended to be a minimal fix suitable for 3.18.

Reported-and-tested-by: Dave Jones 
Cc: Oleg Nesterov 
Cc: Frédéric Weisbecker 
Acked-by: Paul E. McKenney 
Signed-off-by: Andy Lutomirski 
Signed-off-by: Linus Torvalds

sched: Provide update_curr callbacks for stop/idle scheduling classes

2014-11-23T22:14:40+00:00

Chris bisected a NULL pointer deference in task_sched_runtime() to
commit 6e998916dfe3 'sched/cputime: Fix clock_nanosleep()/clock_gettime()
inconsistency'.

Chris observed crashes in atop or other /proc walking programs when he
started fork bombs on his machine.  He assumed that this is a new exit
race, but that does not make any sense when looking at that commit.

What's interesting is that, the commit provides update_curr callbacks
for all scheduling classes except stop_task and idle_task.

While nothing can ever hit that via the clock_nanosleep() and
clock_gettime() interfaces, which have been the target of the commit in
question, the author obviously forgot that there are other code paths
which invoke task_sched_runtime()

do_task_stat(()
 thread_group_cputime_adjusted()
   thread_group_cputime()
     task_cputime()
       task_sched_runtime()
        if (task_current(rq, p) && task_on_rq_queued(p)) {
          update_rq_clock(rq);
          up->sched_class->update_curr(rq);
        }

If the stats are read for a stomp machine task, aka 'migration/N' and
that task is current on its cpu, this will happily call the NULL pointer
of stop_task->update_curr.  Ooops.

Chris observation that this happens faster when he runs the fork bomb
makes sense as the fork bomb will kick migration threads more often so
the probability to hit the issue will increase.

Add the missing update_curr callbacks to the scheduler classes stop_task
and idle_task.  While idle tasks cannot be monitored via /proc we have
other means to hit the idle case.

Fixes: 6e998916dfe3 'sched/cputime: Fix clock_nanosleep()/clock_gettime() inconsistency'
Reported-by: Chris Mason 
Reported-and-tested-by: Borislav Petkov 
Signed-off-by: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: Stanislaw Gruszka 
Cc: Peter Zijlstra 
Signed-off-by: Linus Torvalds

Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

2014-11-20T07:57:58+00:00

Pull RCU updates from Paul E. McKenney:

 - Streamline RCU's use of per-CPU variables, shifting from "cpu"
   arguments to functions to "this_"-style per-CPU variable accessors.

 - Signal-handling RCU updates.

 - Real-time updates.

 - Torture-test updates.

 - Miscellaneous fixes.

 - Documentation updates.

Signed-off-by: Ingo Molnar

sched/deadline: Introduce start_hrtick_dl() for !CONFIG_SCHED_HRTICK

2014-11-16T09:59:03+00:00

Introduce start_hrtick_dl for !CONFIG_SCHED_HRTICK to align with
the fair class.

Signed-off-by: Wanpeng Li 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Juri Lelli 
Cc: Kirill Tkhai 
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/1415670747-58726-1-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar

sched/deadline: Remove unnecessary definitions in cpudeadline.h

2014-11-16T09:59:00+00:00

Actually, cpudl_set() and cpudl_init() can never be used without
CONFIG_SMP.

Signed-off-by: pang.xunlei 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Steven Rostedt 
Cc: Juri Lelli 
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/1415260327-30465-4-git-send-email-pang.xunlei@linaro.org
Signed-off-by: Ingo Molnar

sched/cpupri: Remove unnecessary definitions in cpupri.h

2014-11-16T09:58:59+00:00

Actually, cpupri_set() and cpupri_init() can never be used without
CONFIG_SMP.

Signed-off-by: pang.xunlei 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: Steven Rostedt 
Cc: Juri Lelli 
Cc: "pang.xunlei" 
Cc: Linus Torvalds 
Link: http://lkml.kernel.org/r/1415260327-30465-1-git-send-email-pang.xunlei@linaro.org
Signed-off-by: Ingo Molnar