Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
1 Kernel Lock Torture Test Operation 2 3 CONFIG_LOCK_TORTURE_TEST 4 5 The CONFIG LOCK_TORTURE_TEST config option provides a kernel module 6 that runs torture tests on core kernel locking primitives. The kernel 7 module, 'locktorture', may be built after the fact on the running 8 kernel to be tested, if desired. The tests periodically output status 9 messages via printk(), which can be examined via the dmesg (perhaps 10 grepping for "torture"). The test is started when the module is loaded, 11 and stops when the module is unloaded. This program is based on how RCU 12 is tortured, via rcutorture. 13 14 This torture test consists of creating a number of kernel threads which 15 acquire the lock and hold it for specific amount of time, thus simulating 16 different critical region behaviors. The amount of contention on the lock 17 can be simulated by either enlarging this critical region hold time and/or 18 creating more kthreads. 19 20 21 MODULE PARAMETERS 22 23 This module has the following parameters: 24 25 26 ** Locktorture-specific ** 27 28 nwriters_stress Number of kernel threads that will stress exclusive lock 29 ownership (writers). The default value is twice the number 30 of online CPUs. 31 32 nreaders_stress Number of kernel threads that will stress shared lock 33 ownership (readers). The default is the same amount of writer 34 locks. If the user did not specify nwriters_stress, then 35 both readers and writers be the amount of online CPUs. 36 37 torture_type Type of lock to torture. By default, only spinlocks will 38 be tortured. This module can torture the following locks, 39 with string values as follows: 40 41 o "lock_busted": Simulates a buggy lock implementation. 42 43 o "spin_lock": spin_lock() and spin_unlock() pairs. 44 45 o "spin_lock_irq": spin_lock_irq() and spin_unlock_irq() 46 pairs. 47 48 o "rw_lock": read/write lock() and unlock() rwlock pairs. 49 50 o "rw_lock_irq": read/write lock_irq() and unlock_irq() 51 rwlock pairs. 52 53 o "mutex_lock": mutex_lock() and mutex_unlock() pairs. 54 55 o "rtmutex_lock": rtmutex_lock() and rtmutex_unlock() 56 pairs. Kernel must have CONFIG_RT_MUTEX=y. 57 58 o "rwsem_lock": read/write down() and up() semaphore pairs. 59 60 61 ** Torture-framework (RCU + locking) ** 62 63 shutdown_secs The number of seconds to run the test before terminating 64 the test and powering off the system. The default is 65 zero, which disables test termination and system shutdown. 66 This capability is useful for automated testing. 67 68 onoff_interval The number of seconds between each attempt to execute a 69 randomly selected CPU-hotplug operation. Defaults 70 to zero, which disables CPU hotplugging. In 71 CONFIG_HOTPLUG_CPU=n kernels, locktorture will silently 72 refuse to do any CPU-hotplug operations regardless of 73 what value is specified for onoff_interval. 74 75 onoff_holdoff The number of seconds to wait until starting CPU-hotplug 76 operations. This would normally only be used when 77 locktorture was built into the kernel and started 78 automatically at boot time, in which case it is useful 79 in order to avoid confusing boot-time code with CPUs 80 coming and going. This parameter is only useful if 81 CONFIG_HOTPLUG_CPU is enabled. 82 83 stat_interval Number of seconds between statistics-related printk()s. 84 By default, locktorture will report stats every 60 seconds. 85 Setting the interval to zero causes the statistics to 86 be printed -only- when the module is unloaded, and this 87 is the default. 88 89 stutter The length of time to run the test before pausing for this 90 same period of time. Defaults to "stutter=5", so as 91 to run and pause for (roughly) five-second intervals. 92 Specifying "stutter=0" causes the test to run continuously 93 without pausing, which is the old default behavior. 94 95 shuffle_interval The number of seconds to keep the test threads affinitied 96 to a particular subset of the CPUs, defaults to 3 seconds. 97 Used in conjunction with test_no_idle_hz. 98 99 verbose Enable verbose debugging printing, via printk(). Enabled 100 by default. This extra information is mostly related to 101 high-level errors and reports from the main 'torture' 102 framework. 103 104 105 STATISTICS 106 107 Statistics are printed in the following format: 108 109 spin_lock-torture: Writes: Total: 93746064 Max/Min: 0/0 Fail: 0 110 (A) (B) (C) (D) (E) 111 112 (A): Lock type that is being tortured -- torture_type parameter. 113 114 (B): Number of writer lock acquisitions. If dealing with a read/write primitive 115 a second "Reads" statistics line is printed. 116 117 (C): Number of times the lock was acquired. 118 119 (D): Min and max number of times threads failed to acquire the lock. 120 121 (E): true/false values if there were errors acquiring the lock. This should 122 -only- be positive if there is a bug in the locking primitive's 123 implementation. Otherwise a lock should never fail (i.e., spin_lock()). 124 Of course, the same applies for (C), above. A dummy example of this is 125 the "lock_busted" type. 126 127 USAGE 128 129 The following script may be used to torture locks: 130 131 #!/bin/sh 132 133 modprobe locktorture 134 sleep 3600 135 rmmod locktorture 136 dmesg | grep torture: 137 138 The output can be manually inspected for the error flag of "!!!". 139 One could of course create a more elaborate script that automatically 140 checked for such errors. The "rmmod" command forces a "SUCCESS", 141 "FAILURE", or "RCU_HOTPLUG" indication to be printk()ed. The first 142 two are self-explanatory, while the last indicates that while there 143 were no locking failures, CPU-hotplug problems were detected. 144 145 Also see: Documentation/RCU/torture.txt