linux-stable.git/kernel/cpu.c, branch v4.6.6

cpu/hotplug: Keep enough storage space if SMP=n to avoid array out of bounds scribble

2016-08-10T10:54:49+00:00

commit a7c734140aa36413944eef0f8c660e0e2256357d upstream.

Xiaolong Ye reported lock debug warnings triggered by the following commit:

  8de4a0066106 ("perf/x86: Convert the core to the hotplug state machine")

The bug is the following: the cpuhp_bp_states[] array is cut short when
CONFIG_SMP=n, but the dynamically registered callbacks are stored nevertheless
and happily scribble outside of the array bounds...

We need to store them in case that the state is unregistered so we can invoke
the teardown function. That's independent of CONFIG_SMP. Make sure the array
is large enough.

Reported-by: kernel test robot 
Signed-off-by: Thomas Gleixner 
Cc: Adam Borowski 
Cc: Alexander Shishkin 
Cc: Anna-Maria Gleixner 
Cc: Arnaldo Carvalho de Melo 
Cc: Arnaldo Carvalho de Melo 
Cc: Borislav Petkov 
Cc: Jiri Olsa 
Cc: Kan Liang 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Sebastian Andrzej Siewior 
Cc: Stephane Eranian 
Cc: Vince Weaver 
Cc: lkp@01.org
Cc: tipbuild@zytor.com
Fixes: cff7d378d3fd "cpu/hotplug: Convert to a state machine for the control processor"
Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1607122144560.4083@nanos
Signed-off-by: Ingo Molnar 
Signed-off-by: Greg Kroah-Hartman

cpu/hotplug: Fix rollback during error-out in __cpu_disable()

2016-04-22T07:49:49+00:00

The recent introduction of the hotplug thread which invokes the callbacks on
the plugged cpu, cased the following regression:

If takedown_cpu() fails, then we run into several issues:

 1) The rollback of the target cpu states is not invoked. That leaves the smp
    threads and the hotplug thread in disabled state.

 2) notify_online() is executed due to a missing skip_onerr flag. That causes
    that both CPU_DOWN_FAILED and CPU_ONLINE notifications are invoked which
    confuses quite some notifiers.

 3) The CPU_DOWN_FAILED notification is not invoked on the target CPU. That's
    not an issue per se, but it is inconsistent and in consequence blocks the
    patches which rely on these states being invoked on the target CPU and not
    on the controlling cpu. It also does not preserve the strict call order on
    rollback which is problematic for the ongoing state machine conversion as
    well.

To fix this we add a rollback flag to the remote callback machinery and invoke
the rollback including the CPU_DOWN_FAILED notification on the remote
cpu. Further mark the notify online state with 'skip_onerr' so we don't get a
double invokation.

This workaround will go away once we moved the unplug invocation to the target
cpu itself.

[ tglx: Massaged changelog and moved the CPU_DOWN_FAILED notifiaction to the
  	target cpu ]

Fixes: 4cb28ced23c4 ("cpu/hotplug: Create hotplug threads")
Reported-by: Heiko Carstens 
Signed-off-by: Sebastian Andrzej Siewior 
Cc: linux-s390@vger.kernel.org
Cc: rt@linutronix.de
Cc: Martin Schwidefsky 
Cc: Anna-Maria Gleixner 
Link: http://lkml.kernel.org/r/20160408124015.GA21960@linutronix.de
Signed-off-by: Thomas Gleixner

cpu/hotplug: Document states better

2016-03-12T19:57:38+00:00

Requested-by: Peter Zijlstra 
Signed-off-by: Thomas Gleixner

cpu/hotplug: Fix smpboot thread ordering

2016-03-10T20:21:59+00:00

Commit 931ef163309e moved the smpboot thread park/unpark invocation to the
state machine. The move of the unpark invocation was premature as it depends
on work in progress patches.

As a result cpu down can fail, because rcu synchronization in takedown_cpu()
eventually requires a functional softirq thread. I never encountered the
problem in testing, but 0day testing managed to provide a reliable reproducer.

Remove the smpboot_threads_park() call from the state machine for now and put
it back into the original place after the rcu synchronization.

I'm embarrassed as I knew about the dependency and still managed to get it
wrong. Hotplug induced brain melt seems to be the only sensible explanation
for that.

Fixes: 931ef163309e "cpu/hotplug: Unpark smpboot threads from the state machine"
Reported-by: Fengguang Wu 
Signed-off-by: Thomas Gleixner 
Cc: Peter Zijlstra

cpu/hotplug: Remove redundant state check

2016-03-06T15:59:42+00:00

The check for the AP range in cpuhp_is_ap_state() is redundant after commit
8df3e07e7f21 "cpu/hotplug: Let upcoming cpu bring itself fully up" because all
states above CPUHP_BRINGUP_CPU are invoked on the hotplugged cpu. Remove it.

Reported-by: Richard Cochran 
Signed-off-by: Thomas Gleixner

cpu/hotplug: Plug death reporting race

2016-03-03T09:52:10+00:00

Paul noticed that the conversion of the death reporting introduced a race
where the outgoing cpu might be delayed after waking the controll processor,
so it might not be able to call rcu_report_dead() before being physically
removed, leading to RCU stalls.

We cant call complete after rcu_report_dead(), so instead of going back to
busy polling, simply issue a function call to do the completion.

Fixes: 27d50c7eeb0f "rcu: Make CPU_DYING_IDLE an explicit call"
Reported-by: Paul E. McKenney 
Link: http://lkml.kernel.org/r/20160302201127.GA23440@linux.vnet.ibm.com
Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra

rcu: Make CPU_DYING_IDLE an explicit call

2016-03-01T19:36:58+00:00

Make the RCU CPU_DYING_IDLE callback an explicit function call, so it gets
invoked at the proper place.

Signed-off-by: Thomas Gleixner 
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel 
Cc: Rafael Wysocki 
Cc: "Srivatsa S. Bhat" 
Cc: Peter Zijlstra 
Cc: Arjan van de Ven 
Cc: Sebastian Siewior 
Cc: Rusty Russell 
Cc: Steven Rostedt 
Cc: Oleg Nesterov 
Cc: Tejun Heo 
Cc: Andrew Morton 
Cc: Paul McKenney 
Cc: Linus Torvalds 
Cc: Paul Turner 
Link: http://lkml.kernel.org/r/20160226182341.870167933@linutronix.de
Signed-off-by: Thomas Gleixner

cpu/hotplug: Make wait for dead cpu completion based

2016-03-01T19:36:58+00:00

Kill the busy spinning on the control side and just wait for the hotplugged
cpu to tell that it reached the dead state.

Signed-off-by: Thomas Gleixner 
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel 
Cc: Rafael Wysocki 
Cc: "Srivatsa S. Bhat" 
Cc: Peter Zijlstra 
Cc: Arjan van de Ven 
Cc: Sebastian Siewior 
Cc: Rusty Russell 
Cc: Steven Rostedt 
Cc: Oleg Nesterov 
Cc: Tejun Heo 
Cc: Andrew Morton 
Cc: Paul McKenney 
Cc: Linus Torvalds 
Cc: Paul Turner 
Link: http://lkml.kernel.org/r/20160226182341.776157858@linutronix.de
Signed-off-by: Thomas Gleixner

cpu/hotplug: Let upcoming cpu bring itself fully up

2016-03-01T19:36:57+00:00

Let the upcoming cpu kick the hotplug thread and let itself complete the
bringup. That way the controll side can just wait for the completion or later
when we made the hotplug machinery async not care at all.

Signed-off-by: Thomas Gleixner 
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel 
Cc: Rafael Wysocki 
Cc: "Srivatsa S. Bhat" 
Cc: Peter Zijlstra 
Cc: Arjan van de Ven 
Cc: Sebastian Siewior 
Cc: Rusty Russell 
Cc: Steven Rostedt 
Cc: Oleg Nesterov 
Cc: Tejun Heo 
Cc: Andrew Morton 
Cc: Paul McKenney 
Cc: Linus Torvalds 
Cc: Paul Turner 
Link: http://lkml.kernel.org/r/20160226182341.697655464@linutronix.de
Signed-off-by: Thomas Gleixner

cpu/hotplug: Move online calls to hotplugged cpu

2016-03-01T19:36:57+00:00

Let the hotplugged cpu invoke the setup/teardown callbacks
(CPU_ONLINE/CPU_DOWN_PREPARE) itself.

Signed-off-by: Thomas Gleixner 
Cc: linux-arch@vger.kernel.org
Cc: Rik van Riel 
Cc: Rafael Wysocki 
Cc: "Srivatsa S. Bhat" 
Cc: Peter Zijlstra 
Cc: Arjan van de Ven 
Cc: Sebastian Siewior 
Cc: Rusty Russell 
Cc: Steven Rostedt 
Cc: Oleg Nesterov 
Cc: Tejun Heo 
Cc: Andrew Morton 
Cc: Paul McKenney 
Cc: Linus Torvalds 
Cc: Paul Turner 
Link: http://lkml.kernel.org/r/20160226182341.536364371@linutronix.de
Signed-off-by: Thomas Gleixner