Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 3d916a44 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

documentation: Slow systems can stall RCU grace periods 



If a fast system has a worst-case grace-period duration of (say) ten
seconds, then running the same workload on a system ten times as slow
will get you an RCU CPU stall warning given default stall-warning
timeout settings.  This commit therefore adds this possibility to
stallwarn.txt.

Reported-by: default avatarDaniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent dfa0ee48

Documentation/RCU/stallwarn.txt

+6 −0
Original line number Diff line number Diff line
@@ -70,6 +70,12 @@ o A periodic interrupt whose handler takes longer than the time 
	considerably longer than normal, which can in turn result in

	RCU CPU stall warnings.



o	Testing a workload on a fast system, tuning the stall-warning

	timeout down to just barely avoid RCU CPU stall warnings, and then

	running the same workload with the same stall-warning timeout on a

	slow system.  Note that thermal throttling and on-demand governors

	can cause a single system to be sometimes fast and sometimes slow!



o	A hardware or software issue shuts off the scheduler-clock

	interrupt on a CPU that is not in dyntick-idle mode.  This

	problem really has happened, and seems to be most likely to