148 lines
5.6 KiB
Plaintext
148 lines
5.6 KiB
Plaintext
Kernel Lock Torture Test Operation
|
|
|
|
CONFIG_LOCK_TORTURE_TEST
|
|
|
|
The CONFIG LOCK_TORTURE_TEST config option provides a kernel module
|
|
that runs torture tests on core kernel locking primitives. The kernel
|
|
module, 'locktorture', may be built after the fact on the running
|
|
kernel to be tested, if desired. The tests periodically output status
|
|
messages via printk(), which can be examined via the dmesg (perhaps
|
|
grepping for "torture"). The test is started when the module is loaded,
|
|
and stops when the module is unloaded. This program is based on how RCU
|
|
is tortured, via rcutorture.
|
|
|
|
This torture test consists of creating a number of kernel threads which
|
|
acquire the lock and hold it for specific amount of time, thus simulating
|
|
different critical region behaviors. The amount of contention on the lock
|
|
can be simulated by either enlarging this critical region hold time and/or
|
|
creating more kthreads.
|
|
|
|
|
|
MODULE PARAMETERS
|
|
|
|
This module has the following parameters:
|
|
|
|
|
|
** Locktorture-specific **
|
|
|
|
nwriters_stress Number of kernel threads that will stress exclusive lock
|
|
ownership (writers). The default value is twice the number
|
|
of online CPUs.
|
|
|
|
nreaders_stress Number of kernel threads that will stress shared lock
|
|
ownership (readers). The default is the same amount of writer
|
|
locks. If the user did not specify nwriters_stress, then
|
|
both readers and writers be the amount of online CPUs.
|
|
|
|
torture_type Type of lock to torture. By default, only spinlocks will
|
|
be tortured. This module can torture the following locks,
|
|
with string values as follows:
|
|
|
|
o "lock_busted": Simulates a buggy lock implementation.
|
|
|
|
o "spin_lock": spin_lock() and spin_unlock() pairs.
|
|
|
|
o "spin_lock_irq": spin_lock_irq() and spin_unlock_irq()
|
|
pairs.
|
|
|
|
o "rw_lock": read/write lock() and unlock() rwlock pairs.
|
|
|
|
o "rw_lock_irq": read/write lock_irq() and unlock_irq()
|
|
rwlock pairs.
|
|
|
|
o "mutex_lock": mutex_lock() and mutex_unlock() pairs.
|
|
|
|
o "rwsem_lock": read/write down() and up() semaphore pairs.
|
|
|
|
torture_runnable Start locktorture at boot time in the case where the
|
|
module is built into the kernel, otherwise wait for
|
|
torture_runnable to be set via sysfs before starting.
|
|
By default it will begin once the module is loaded.
|
|
|
|
|
|
** Torture-framework (RCU + locking) **
|
|
|
|
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.
|
|
|
|
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
|
|
CONFIG_HOTPLUG_CPU=n kernels, locktorture 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
|
|
locktorture 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. This parameter is only useful if
|
|
CONFIG_HOTPLUG_CPU is enabled.
|
|
|
|
stat_interval Number of seconds between statistics-related printk()s.
|
|
By default, locktorture will report stats every 60 seconds.
|
|
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.
|
|
|
|
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.
|
|
|
|
verbose Enable verbose debugging printing, via printk(). Enabled
|
|
by default. This extra information is mostly related to
|
|
high-level errors and reports from the main 'torture'
|
|
framework.
|
|
|
|
|
|
STATISTICS
|
|
|
|
Statistics are printed in the following format:
|
|
|
|
spin_lock-torture: Writes: Total: 93746064 Max/Min: 0/0 Fail: 0
|
|
(A) (B) (C) (D) (E)
|
|
|
|
(A): Lock type that is being tortured -- torture_type parameter.
|
|
|
|
(B): Number of writer lock acquisitions. If dealing with a read/write primitive
|
|
a second "Reads" statistics line is printed.
|
|
|
|
(C): Number of times the lock was acquired.
|
|
|
|
(D): Min and max number of times threads failed to acquire the lock.
|
|
|
|
(E): true/false values if there were errors acquiring the lock. This should
|
|
-only- be positive if there is a bug in the locking primitive's
|
|
implementation. Otherwise a lock should never fail (i.e., spin_lock()).
|
|
Of course, the same applies for (C), above. A dummy example of this is
|
|
the "lock_busted" type.
|
|
|
|
USAGE
|
|
|
|
The following script may be used to torture locks:
|
|
|
|
#!/bin/sh
|
|
|
|
modprobe locktorture
|
|
sleep 3600
|
|
rmmod locktorture
|
|
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",
|
|
"FAILURE", or "RCU_HOTPLUG" indication to be printk()ed. The first
|
|
two are self-explanatory, while the last indicates that while there
|
|
were no locking failures, CPU-hotplug problems were detected.
|
|
|
|
Also see: Documentation/RCU/torture.txt
|