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169 lines
5.6 KiB
169 lines
5.6 KiB
================================== |
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Kernel Lock Torture Test Operation |
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================================== |
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CONFIG_LOCK_TORTURE_TEST |
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======================== |
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The CONFIG LOCK_TORTURE_TEST config option provides a kernel module |
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that runs torture tests on core kernel locking primitives. The kernel |
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module, 'locktorture', may be built after the fact on the running |
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kernel to be tested, if desired. The tests periodically output status |
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messages via printk(), which can be examined via the dmesg (perhaps |
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grepping for "torture"). The test is started when the module is loaded, |
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and stops when the module is unloaded. This program is based on how RCU |
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is tortured, via rcutorture. |
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This torture test consists of creating a number of kernel threads which |
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acquire the lock and hold it for specific amount of time, thus simulating |
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different critical region behaviors. The amount of contention on the lock |
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can be simulated by either enlarging this critical region hold time and/or |
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creating more kthreads. |
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Module Parameters |
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================= |
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This module has the following parameters: |
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Locktorture-specific |
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-------------------- |
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nwriters_stress |
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Number of kernel threads that will stress exclusive lock |
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ownership (writers). The default value is twice the number |
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of online CPUs. |
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nreaders_stress |
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Number of kernel threads that will stress shared lock |
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ownership (readers). The default is the same amount of writer |
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locks. If the user did not specify nwriters_stress, then |
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both readers and writers be the amount of online CPUs. |
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torture_type |
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Type of lock to torture. By default, only spinlocks will |
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be tortured. This module can torture the following locks, |
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with string values as follows: |
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- "lock_busted": |
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Simulates a buggy lock implementation. |
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- "spin_lock": |
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spin_lock() and spin_unlock() pairs. |
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- "spin_lock_irq": |
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spin_lock_irq() and spin_unlock_irq() pairs. |
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- "rw_lock": |
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read/write lock() and unlock() rwlock pairs. |
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- "rw_lock_irq": |
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read/write lock_irq() and unlock_irq() |
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rwlock pairs. |
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- "mutex_lock": |
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mutex_lock() and mutex_unlock() pairs. |
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- "rtmutex_lock": |
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rtmutex_lock() and rtmutex_unlock() pairs. |
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Kernel must have CONFIG_RT_MUTEX=y. |
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- "rwsem_lock": |
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read/write down() and up() semaphore pairs. |
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Torture-framework (RCU + locking) |
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--------------------------------- |
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shutdown_secs |
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The number of seconds to run the test before terminating |
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the test and powering off the system. The default is |
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zero, which disables test termination and system shutdown. |
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This capability is useful for automated testing. |
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onoff_interval |
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The number of seconds between each attempt to execute a |
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randomly selected CPU-hotplug operation. Defaults |
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to zero, which disables CPU hotplugging. In |
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CONFIG_HOTPLUG_CPU=n kernels, locktorture will silently |
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refuse to do any CPU-hotplug operations regardless of |
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what value is specified for onoff_interval. |
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onoff_holdoff |
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The number of seconds to wait until starting CPU-hotplug |
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operations. This would normally only be used when |
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locktorture was built into the kernel and started |
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automatically at boot time, in which case it is useful |
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in order to avoid confusing boot-time code with CPUs |
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coming and going. This parameter is only useful if |
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CONFIG_HOTPLUG_CPU is enabled. |
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stat_interval |
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Number of seconds between statistics-related printk()s. |
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By default, locktorture will report stats every 60 seconds. |
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Setting the interval to zero causes the statistics to |
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be printed -only- when the module is unloaded. |
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stutter |
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The length of time to run the test before pausing for this |
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same period of time. Defaults to "stutter=5", so as |
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to run and pause for (roughly) five-second intervals. |
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Specifying "stutter=0" causes the test to run continuously |
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without pausing. |
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shuffle_interval |
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The number of seconds to keep the test threads affinitied |
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to a particular subset of the CPUs, defaults to 3 seconds. |
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Used in conjunction with test_no_idle_hz. |
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verbose |
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Enable verbose debugging printing, via printk(). Enabled |
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by default. This extra information is mostly related to |
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high-level errors and reports from the main 'torture' |
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framework. |
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Statistics |
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========== |
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Statistics are printed in the following format:: |
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spin_lock-torture: Writes: Total: 93746064 Max/Min: 0/0 Fail: 0 |
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(A) (B) (C) (D) (E) |
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(A): Lock type that is being tortured -- torture_type parameter. |
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(B): Number of writer lock acquisitions. If dealing with a read/write |
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primitive a second "Reads" statistics line is printed. |
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(C): Number of times the lock was acquired. |
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(D): Min and max number of times threads failed to acquire the lock. |
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(E): true/false values if there were errors acquiring the lock. This should |
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-only- be positive if there is a bug in the locking primitive's |
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implementation. Otherwise a lock should never fail (i.e., spin_lock()). |
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Of course, the same applies for (C), above. A dummy example of this is |
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the "lock_busted" type. |
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Usage |
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===== |
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The following script may be used to torture locks:: |
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#!/bin/sh |
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modprobe locktorture |
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sleep 3600 |
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rmmod locktorture |
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dmesg | grep torture: |
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The output can be manually inspected for the error flag of "!!!". |
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One could of course create a more elaborate script that automatically |
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checked for such errors. The "rmmod" command forces a "SUCCESS", |
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"FAILURE", or "RCU_HOTPLUG" indication to be printk()ed. The first |
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two are self-explanatory, while the last indicates that while there |
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were no locking failures, CPU-hotplug problems were detected. |
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Also see: Documentation/RCU/torture.rst
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