Merge tag 'pinctrl-for-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw...

[firefly-linux-kernel-4.4.55.git] / Documentation / RCU / torture.txt

diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt
index d67068d0d2b9818cf3d5344c42452a2d395e9ff0..375d3fb714370cd9289ad1c62e893fe748f1cccf 100644 (file)
--- a/Documentation/RCU/torture.txt
+++ b/Documentation/RCU/torture.txt
@@ -69,6 +69,13 @@ onoff_interval
                CPU-hotplug operations regardless of what value is
                specified for onoff_interval.
 
+onoff_holdoff  The number of seconds to wait until starting CPU-hotplug
+               operations.  This would normally only be used when
+               rcutorture was built into the kernel and started
+               automatically at boot time, in which case it is useful
+               in order to avoid confusing boot-time code with CPUs
+               coming and going.
+
 shuffle_interval
                The number of seconds to keep the test threads affinitied
                to a particular subset of the CPUs, defaults to 3 seconds.
@@ -79,6 +86,24 @@ shutdown_secs        The number of seconds to run the test before terminating
                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.
@@ -271,11 +296,13 @@ The following script may be used to torture RCU:
        #!/bin/sh
 
        modprobe rcutorture
-       sleep 100
+       sleep 3600
        rmmod rcutorture
        dmesg | grep torture:
 
 The output can be manually inspected for the error flag of "!!!".
 One could of course create a more elaborate script that automatically
-checked for such errors.  The "rmmod" command forces a "SUCCESS" or
-"FAILURE" indication to be printk()ed.
+checked for such errors.  The "rmmod" command forces a "SUCCESS",
+"FAILURE", or "RCU_HOTPLUG" indication to be printk()ed.  The first
+two are self-explanatory, while the last indicates that while there
+were no RCU failures, CPU-hotplug problems were detected.