command (perhaps grepping for "torture"). The test is started
when the module is loaded, and stops when the module is unloaded.
-However, actually setting this config option to "y" results in the system
-running the test immediately upon boot, and ending only when the system
-is taken down. Normally, one will instead want to build the system
-with CONFIG_RCU_TORTURE_TEST=m and to use modprobe and rmmod to control
-the test, perhaps using a script similar to the one shown at the end of
-this document. Note that you will need CONFIG_MODULE_UNLOAD in order
-to be able to end the test.
+CONFIG_RCU_TORTURE_TEST_RUNNABLE
+
+It is also possible to specify CONFIG_RCU_TORTURE_TEST=y, which will
+result in the tests being loaded into the base kernel. In this case,
+the CONFIG_RCU_TORTURE_TEST_RUNNABLE config option is used to specify
+whether the RCU torture tests are to be started immediately during
+boot or whether the /proc/sys/kernel/rcutorture_runnable file is used
+to enable them. This /proc file can be used to repeatedly pause and
+restart the tests, regardless of the initial state specified by the
+CONFIG_RCU_TORTURE_TEST_RUNNABLE config option.
+
+You will normally -not- want to start the RCU torture tests during boot
+(and thus the default is CONFIG_RCU_TORTURE_TEST_RUNNABLE=n), but doing
+this can sometimes be useful in finding boot-time bugs.
MODULE PARAMETERS
This module has the following parameters:
+irqreaders Says to invoke RCU readers from irq level. This is currently
+ done via timers. Defaults to "1" for variants of RCU that
+ permit this. (Or, more accurately, variants of RCU that do
+ -not- permit this know to ignore this variable.)
+
+nfakewriters This is the number of RCU fake writer threads to run. Fake
+ writer threads repeatedly use the synchronous "wait for
+ current readers" function of the interface selected by
+ torture_type, with a delay between calls to allow for various
+ different numbers of writers running in parallel.
+ nfakewriters defaults to 4, which provides enough parallelism
+ to trigger special cases caused by multiple writers, such as
+ the synchronize_srcu() early return optimization.
+
nreaders This is the number of RCU reading threads supported.
The default is twice the number of CPUs. Why twice?
To properly exercise RCU implementations with preemptible
read-side critical sections.
+shuffle_interval
+ The number of seconds to keep the test threads affinitied
+ to a particular subset of the CPUs, defaults to 3 seconds.
+ Used in conjunction with test_no_idle_hz.
+
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.
be printed -only- when the module is unloaded, and this
is the default.
-shuffle_interval
- The number of seconds to keep the test threads affinitied
- to a particular subset of the CPUs. Used in conjunction
- with test_no_idle_hz.
+stutter The length of time to run the test before pausing for this
+ same period of time. Defaults to "stutter=5", so as
+ to run and pause for (roughly) five-second intervals.
+ Specifying "stutter=0" causes the test to run continuously
+ without pausing, which is the old default behavior.
test_no_idle_hz Whether or not to test the ability of RCU to operate in
a kernel that disables the scheduling-clock interrupt to
idle CPUs. Boolean parameter, "1" to test, "0" otherwise.
+ Defaults to omitting this test.
-torture_type The type of RCU to test: "rcu" for the rcu_read_lock()
- API, "rcu_bh" for the rcu_read_lock_bh() API, and "srcu"
- for the "srcu_read_lock()" API.
+torture_type The type of RCU to test: "rcu" for the rcu_read_lock() API,
+ "rcu_sync" for rcu_read_lock() with synchronous reclamation,
+ "rcu_bh" for the rcu_read_lock_bh() API, "rcu_bh_sync" for
+ rcu_read_lock_bh() with synchronous reclamation, "srcu" for
+ the "srcu_read_lock()" API, and "sched" for the use of
+ preempt_disable() together with synchronize_sched().
verbose Enable debug printk()s. Default is disabled.
The entries are as follows:
-o "ggp": The number of counter flips (or batches) since boot.
-
o "rtc": The hexadecimal address of the structure currently visible
to readers.
o "Reader Batch": Another histogram of "ages" of structures seen
by readers, but in terms of counter flips (or batches) rather
than in terms of grace periods. The legal number of non-zero
- entries is again two. The reason for this separate view is
- that it is easier to get the third entry to show up in the
+ entries is again two. The reason for this separate view is that
+ it is sometimes easier to get the third entry to show up in the
"Reader Batch" list than in the "Reader Pipe" list.
o "Free-Block Circulation": Shows the number of torture structures
as it is only incremented if a torture structure's counter
somehow gets incremented farther than it should.
+Different implementations of RCU can provide implementation-specific
+additional information. For example, SRCU provides the following:
+
+ srcu-torture: rtc: f8cf46a8 ver: 355 tfle: 0 rta: 356 rtaf: 0 rtf: 346 rtmbe: 0
+ srcu-torture: Reader Pipe: 559738 939 0 0 0 0 0 0 0 0 0
+ srcu-torture: Reader Batch: 560434 243 0 0 0 0 0 0 0 0
+ srcu-torture: Free-Block Circulation: 355 354 353 352 351 350 349 348 347 346 0
+ srcu-torture: per-CPU(idx=1): 0(0,1) 1(0,1) 2(0,0) 3(0,1)
+
+The first four lines are similar to those for RCU. The last line shows
+the per-CPU counter state. The numbers in parentheses are the values
+of the "old" and "current" counters for the corresponding CPU. The
+"idx" value maps the "old" and "current" values to the underlying array,
+and is useful for debugging.
+
USAGE
git.openpandora.org / pandora-kernel.git / blobdiff