rcu: Add CPU-stall capability to rcutorture
Add module parameters to rcutorture that induce a CPU stall.
The stall_cpu parameter specifies how long to stall in seconds,
defaulting to zero, which indicates no stalling is to be undertaken.
The stall_cpu_holdoff parameter specifies how many seconds after
insmod (or boot, if rcutorture is built into the kernel) that this
stall is to start. The default value for stall_cpu_holdoff is ten
seconds.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt
index d25be87..375d3fb 100644
--- a/Documentation/RCU/torture.txt
+++ b/Documentation/RCU/torture.txt
@@ -86,6 +86,24 @@
zero, which disables test termination and system shutdown.
This capability is useful for automated testing.
+stall_cpu The number of seconds that a CPU should be stalled while
+ within both an rcu_read_lock() and a preempt_disable().
+ This stall happens only once per rcutorture run.
+ If you need multiple stalls, use modprobe and rmmod to
+ repeatedly run rcutorture. The default for stall_cpu
+ is zero, which prevents rcutorture from stalling a CPU.
+
+ Note that attempts to rmmod rcutorture while the stall
+ is ongoing will hang, so be careful what value you
+ choose for this module parameter! In addition, too-large
+ values for stall_cpu might well induce failures and
+ warnings in other parts of the kernel. You have been
+ warned!
+
+stall_cpu_holdoff
+ The number of seconds to wait after rcutorture starts
+ before stalling a CPU. Defaults to 10 seconds.
+
stat_interval The number of seconds between output of torture
statistics (via printk()). Regardless of the interval,
statistics are printed when the module is unloaded.