1# SPDX-License-Identifier: GPL-2.0-only 2# 3# RCU-related debugging configuration options 4# 5 6menu "RCU Debugging" 7 8config PROVE_RCU 9 def_bool PROVE_LOCKING 10 11config PROVE_RCU_LIST 12 bool "RCU list lockdep debugging" 13 depends on PROVE_RCU && RCU_EXPERT 14 default n 15 help 16 Enable RCU lockdep checking for list usages. By default it is 17 turned off since there are several list RCU users that still 18 need to be converted to pass a lockdep expression. To prevent 19 false-positive splats, we keep it default disabled but once all 20 users are converted, we can remove this config option. 21 22config TORTURE_TEST 23 tristate 24 default n 25 26config RCU_SCALE_TEST 27 tristate "performance tests for RCU" 28 depends on DEBUG_KERNEL 29 select TORTURE_TEST 30 default n 31 help 32 This option provides a kernel module that runs performance 33 tests on the RCU infrastructure. The kernel module may be built 34 after the fact on the running kernel to be tested, if desired. 35 36 Say Y here if you want RCU performance tests to be built into 37 the kernel. 38 Say M if you want the RCU performance tests to build as a module. 39 Say N if you are unsure. 40 41config RCU_TORTURE_TEST 42 tristate "torture tests for RCU" 43 depends on DEBUG_KERNEL 44 select TORTURE_TEST 45 default n 46 help 47 This option provides a kernel module that runs torture tests 48 on the RCU infrastructure. The kernel module may be built 49 after the fact on the running kernel to be tested, if desired. 50 51 Say Y here if you want RCU torture tests to be built into 52 the kernel. 53 Say M if you want the RCU torture tests to build as a module. 54 Say N if you are unsure. 55 56config RCU_REF_SCALE_TEST 57 tristate "Scalability tests for read-side synchronization (RCU and others)" 58 depends on DEBUG_KERNEL 59 select TORTURE_TEST 60 default n 61 help 62 This option provides a kernel module that runs performance tests 63 useful comparing RCU with various read-side synchronization mechanisms. 64 The kernel module may be built after the fact on the running kernel to be 65 tested, if desired. 66 67 Say Y here if you want these performance tests built into the kernel. 68 Say M if you want to build it as a module instead. 69 Say N if you are unsure. 70 71config RCU_CPU_STALL_TIMEOUT 72 int "RCU CPU stall timeout in seconds" 73 depends on RCU_STALL_COMMON 74 range 3 300 75 default 21 76 help 77 If a given RCU grace period extends more than the specified 78 number of seconds, a CPU stall warning is printed. If the 79 RCU grace period persists, additional CPU stall warnings are 80 printed at more widely spaced intervals. 81 82config RCU_EXP_CPU_STALL_TIMEOUT 83 int "Expedited RCU CPU stall timeout in milliseconds" 84 depends on RCU_STALL_COMMON 85 range 0 300000 86 default 0 87 help 88 If a given expedited RCU grace period extends more than the 89 specified number of milliseconds, a CPU stall warning is printed. 90 If the RCU grace period persists, additional CPU stall warnings 91 are printed at more widely spaced intervals. A value of zero 92 says to use the RCU_CPU_STALL_TIMEOUT value converted from 93 seconds to milliseconds. 94 95config RCU_CPU_STALL_CPUTIME 96 bool "Provide additional RCU stall debug information" 97 depends on RCU_STALL_COMMON 98 default n 99 help 100 Collect statistics during the sampling period, such as the number of 101 (hard interrupts, soft interrupts, task switches) and the cputime of 102 (hard interrupts, soft interrupts, kernel tasks) are added to the 103 RCU stall report. For multiple continuous RCU stalls, all sampling 104 periods begin at half of the first RCU stall timeout. 105 The boot option rcupdate.rcu_cpu_stall_cputime has the same function 106 as this one, but will override this if it exists. 107 108config RCU_CPU_STALL_NOTIFIER 109 bool "Provide RCU CPU-stall notifiers" 110 depends on RCU_STALL_COMMON 111 depends on DEBUG_KERNEL 112 depends on RCU_EXPERT 113 default n 114 help 115 WARNING: You almost certainly do not want this!!! 116 117 Enable RCU CPU-stall notifiers, which are invoked just before 118 printing the RCU CPU stall warning. As such, bugs in notifier 119 callbacks can prevent stall warnings from being printed. 120 And the whole reason that a stall warning is being printed is 121 that something is hung up somewhere. Therefore, the notifier 122 callbacks must be written extremely carefully, preferably 123 containing only lockless code. After all, it is quite possible 124 that the whole reason that the RCU CPU stall is happening in 125 the first place is that someone forgot to release whatever lock 126 that you are thinking of acquiring. In which case, having your 127 notifier callback acquire that lock will hang, preventing the 128 RCU CPU stall warning from appearing. 129 130 Say Y here if you want RCU CPU stall notifiers (you don't want them) 131 Say N if you are unsure. 132 133config RCU_TRACE 134 bool "Enable tracing for RCU" 135 depends on DEBUG_KERNEL 136 default y if TREE_RCU 137 select TRACE_CLOCK 138 help 139 This option enables additional tracepoints for ftrace-style 140 event tracing. 141 142 Say Y here if you want to enable RCU tracing 143 Say N if you are unsure. 144 145config RCU_EQS_DEBUG 146 bool "Provide debugging asserts for adding NO_HZ support to an arch" 147 depends on DEBUG_KERNEL 148 help 149 This option provides consistency checks in RCU's handling of 150 NO_HZ. These checks have proven quite helpful in detecting 151 bugs in arch-specific NO_HZ code. 152 153 Say N here if you need ultimate kernel/user switch latencies 154 Say Y if you are unsure 155 156config RCU_STRICT_GRACE_PERIOD 157 bool "Provide debug RCU implementation with short grace periods" 158 depends on DEBUG_KERNEL && RCU_EXPERT && NR_CPUS <= 4 && !TINY_RCU 159 default n 160 select PREEMPT_COUNT if PREEMPT=n 161 help 162 Select this option to build an RCU variant that is strict about 163 grace periods, making them as short as it can. This limits 164 scalability, destroys real-time response, degrades battery 165 lifetime and kills performance. Don't try this on large 166 machines, as in systems with more than about 10 or 20 CPUs. 167 But in conjunction with tools like KASAN, it can be helpful 168 when looking for certain types of RCU usage bugs, for example, 169 too-short RCU read-side critical sections. 170 171endmenu # "RCU Debugging" 172