command (perhaps grepping for "torture"). The test is started
when the module is loaded, and stops when the module is unloaded.
-
-MODULE PARAMETERS
-
-This module has the following parameters:
-
-fqs_duration Duration (in microseconds) of artificially induced bursts
- of force_quiescent_state() invocations. In RCU
- implementations having force_quiescent_state(), these
- bursts help force races between forcing a given grace
- period and that grace period ending on its own.
-
-fqs_holdoff Holdoff time (in microseconds) between consecutive calls
- to force_quiescent_state() within a burst.
-
-fqs_stutter Wait time (in seconds) between consecutive bursts
- of calls to force_quiescent_state().
-
-gp_normal Make the fake writers use normal synchronous grace-period
- primitives.
-
-gp_exp Make the fake writers use expedited synchronous grace-period
- primitives. If both gp_normal and gp_exp are set, or
- if neither gp_normal nor gp_exp are set, then randomly
- choose the primitive so that about 50% are normal and
- 50% expedited. By default, neither are set, which
- gives best overall test coverage.
-
-irqreader 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.)
-
-n_barrier_cbs If this is nonzero, RCU barrier testing will be conducted,
- in which case n_barrier_cbs specifies the number of
- RCU callbacks (and corresponding kthreads) to use for
- this testing. The value cannot be negative. If you
- specify this to be non-zero when torture_type indicates a
- synchronous RCU implementation (one for which a member of
- the synchronize_rcu() rather than the call_rcu() family is
- used -- see the documentation for torture_type below), an
- error will be reported and no testing will be carried out.
-
-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.
-
-onoff_interval
- The number of seconds between each attempt to execute a
- randomly selected CPU-hotplug operation. Defaults to
- zero, which disables CPU hotplugging. In HOTPLUG_CPU=n
- kernels, rcutorture will silently refuse to do any
- 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.
- Used in conjunction with test_no_idle_hz.
-
-shutdown_secs The number of seconds to run the test before terminating
- the test and powering off the system. The default is
- 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.
- Setting the interval to zero causes the statistics to
- be printed -only- when the module is unloaded, and this
- is the default.
-
-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_boost Whether or not to test the ability of RCU to do priority
- boosting. Defaults to "test_boost=1", which performs
- RCU priority-inversion testing only if the selected
- RCU implementation supports priority boosting. Specifying
- "test_boost=0" never performs RCU priority-inversion
- testing. Specifying "test_boost=2" performs RCU
- priority-inversion testing even if the selected RCU
- implementation does not support RCU priority boosting,
- which can be used to test rcutorture's ability to
- carry out RCU priority-inversion testing.
-
-test_boost_interval
- The number of seconds in an RCU priority-inversion test
- cycle. Defaults to "test_boost_interval=7". It is
- usually wise for this value to be relatively prime to
- the value selected for "stutter".
-
-test_boost_duration
- The number of seconds to do RCU priority-inversion testing
- within any given "test_boost_interval". Defaults to
- "test_boost_duration=4".
-
-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, with string values as follows:
-
- "rcu": rcu_read_lock(), rcu_read_unlock() and call_rcu(),
- along with expedited, synchronous, and polling
- variants.
-
- "rcu_bh": rcu_read_lock_bh(), rcu_read_unlock_bh(), and
- call_rcu_bh(), along with expedited and synchronous
- variants.
-
- "rcu_busted": This tests an intentionally incorrect version
- of RCU in order to help test rcutorture itself.
-
- "srcu": srcu_read_lock(), srcu_read_unlock() and
- call_srcu(), along with expedited and
- synchronous variants.
-
- "sched": preempt_disable(), preempt_enable(), and
- call_rcu_sched(), along with expedited,
- synchronous, and polling variants.
-
- "tasks": voluntary context switch and call_rcu_tasks(),
- along with expedited and synchronous variants.
-
- Defaults to "rcu".
-
-verbose Enable debug printk()s. Default is disabled.
-
+Module parameters are prefixed by "rcutorture." in
+Documentation/admin-guide/kernel-parameters.txt.
OUTPUT