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Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest

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On Fri, 12 May 2017 11:35:59 -0700
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com> wrote:

> On Fri, May 12, 2017 at 01:15:46PM -0400, Steven Rostedt wrote:
> > From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>
> > 
> > Allow get_online_cpus() to be recursive. If a lock is taken while under
> > "get_online_cpus()", it can call get_online_cpus() as well, just as long as
> > it is never held without being under get_online_cpus(), but then calling it.
> > 
> >    GOC() -> Lock(X) -> GOC()
> > 
> > is OK, as long as
> > 
> >    Lock(X) -> GOC()
> > 
> > does not exist.
> > 
> > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>  
> 
> Does ->goc_depth also need to be initialized in include/linux/init_task.h?
> 
> It seems like C-language initialization-to-zero would cover this,
> but there is a lot of initialization to zero values in init_task.h
> (including but not limited to some RCU stuff).

I assumed that it would just initialize it to zero.

OK, I need to add this:

-- Steve

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index fffe49f..be7f71b 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -375,7 +375,7 @@ extern struct pin_cookie lock_pin_lock(struct lockdep_map *lock);
 extern void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie);
 extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
 
-# define INIT_LOCKDEP				.lockdep_recursion = 0, .lockdep_reclaim_gfp = 0,
+# define INIT_LOCKDEP				.lockdep_recursion = 0, .lockdep_reclaim_gfp = 0, .goc_depth = 0,
 
 #define lockdep_depth(tsk)	(debug_locks ? (tsk)->lockdep_depth : 0)
 

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[RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest Steven Rostedt <rostedt@goodmis.org> - 2017-05-12 19:30 +0200
  Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-12 20:40 +0200
    Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest Steven Rostedt <rostedt@goodmis.org> - 2017-05-12 20:50 +0200
      Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2017-05-12 21:00 +0200
  Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest Thomas Gleixner <tglx@linutronix.de> - 2017-05-13 00:20 +0200
    Re: [RFC][PATCH 2/5] cpu-hotplug: Allow get_online_cpus() to nest Steven Rostedt <rostedt@goodmis.org> - 2017-05-13 02:30 +0200

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