Paul E. McKenney 97535791d8 rcu: Allow for page faults in NMI handlers ... commit 28585a8326 upstream. A number of architecture invoke rcu_irq_enter() on exception entry in order to allow RCU read-side critical sections in the exception handler when the exception is from an idle or nohz_full CPU. This works, at least unless the exception happens in an NMI handler. In that case, rcu_nmi_enter() would already have exited the extended quiescent state, which would mean that rcu_irq_enter() would (incorrectly) cause RCU to think that it is again in an extended quiescent state. This will in turn result in lockdep splats in response to later RCU read-side critical sections. This commit therefore causes rcu_irq_enter() and rcu_irq_exit() to take no action if there is an rcu_nmi_enter() in effect, thus avoiding the unscheduled return to RCU quiescent state. This in turn should make the kernel safe for on-demand RCU voyeurism. Link: http://lkml.kernel.org/r/20170922211022.GA18084@linux.vnet.ibm.com Fixes: 0be964be0 ("module: Sanitize RCU usage and locking") Reported-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2017-10-18 09:35:38 +02:00
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Makefile	rcutorture: Add RCU grace-period performance tests	2016-03-31 13:37:38 -07:00
rcu.h	rcu: Narrow early boot window of illegal synchronous grace periods	2017-01-26 08:24:37 +01:00
rcuperf.c	rcuperf: Consistently insert space between flag and message	2016-08-22 10:06:16 -07:00
rcutorture.c	Merge branches 'doc.2016.08.22c', 'exp.2016.08.22c', 'fixes.2016.09.14a', 'hotplug.2016.08.22c' and 'torture.2016.08.22c' into HEAD	2016-09-14 12:58:49 -07:00
srcu.c	rcu: Add rcu_normal kernel parameter to suppress expediting	2015-12-04 12:26:53 -08:00
sync.c	locking, rcu, cgroup: Avoid synchronize_sched() in __cgroup_procs_write()	2016-08-18 15:36:59 +02:00
tiny.c	rcu: Remove cond_resched() from Tiny synchronize_sched()	2017-01-26 08:24:37 +01:00
tiny_plugin.h	rcu: Narrow early boot window of illegal synchronous grace periods	2017-01-26 08:24:37 +01:00
tree.c	rcu: Allow for page faults in NMI handlers	2017-10-18 09:35:38 +02:00
tree.h	rcu: Drive expedited grace periods from workqueue	2016-08-22 09:30:25 -07:00
tree_exp.h	rcu: Narrow early boot window of illegal synchronous grace periods	2017-01-26 08:24:37 +01:00
tree_plugin.h	rcu: Add memory barriers for NOCB leader wakeup	2017-07-21 07:42:22 +02:00
tree_trace.c	rcu: Drive expedited grace periods from workqueue	2016-08-22 09:30:25 -07:00
update.c	rcu: Narrow early boot window of illegal synchronous grace periods	2017-01-26 08:24:37 +01:00