projects/linux·blob assoc-array-fixes · refs

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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_TORTURE_TEST_CHK_RDR_STATE
57 bool "Check rcutorture reader state"
58 depends on RCU_TORTURE_TEST
59 default n
60 help
61 This option causes rcutorture to check the desired rcutorture
62 reader state for each segment against the actual context.
63 Note that PREEMPT_COUNT must be enabled if the preempt-disabled
64 and bh-disabled checks are to take effect, and that PREEMPT_RCU
65 must be enabled for the RCU-nesting checks to take effect.
66 These checks add overhead, and this Kconfig options is therefore
67 disabled by default.
68
69 Say Y here if you want rcutorture reader contexts checked.
70 Say N if you are unsure.
71
72config RCU_TORTURE_TEST_LOG_CPU
73 bool "Log CPU for rcutorture failures"
74 depends on RCU_TORTURE_TEST
75 default n
76 help
77 This option causes rcutorture to decorate each entry of its
78 log of failure/close-call rcutorture reader segments with the
79 number of the CPU that the reader was running on at the time.
80 This information can be useful, but it does incur additional
81 overhead, overhead that can make both failures and close calls
82 less probable.
83
84 Say Y here if you want CPU IDs logged.
85 Say N if you are unsure.
86
87config RCU_TORTURE_TEST_LOG_GP
88 bool "Log grace-period numbers for rcutorture failures"
89 depends on RCU_TORTURE_TEST
90 default n
91 help
92 This option causes rcutorture to decorate each entry of its
93 log of failure/close-call rcutorture reader segments with the
94 corresponding grace-period sequence numbers. This information
95 can be useful, but it does incur additional overhead, overhead
96 that can make both failures and close calls less probable.
97
98 Say Y here if you want grace-period sequence numbers logged.
99 Say N if you are unsure.
100
101config RCU_REF_SCALE_TEST
102 tristate "Scalability tests for read-side synchronization (RCU and others)"
103 depends on DEBUG_KERNEL
104 select TORTURE_TEST
105 default n
106 help
107 This option provides a kernel module that runs performance tests
108 useful comparing RCU with various read-side synchronization mechanisms.
109 The kernel module may be built after the fact on the running kernel to be
110 tested, if desired.
111
112 Say Y here if you want these performance tests built into the kernel.
113 Say M if you want to build it as a module instead.
114 Say N if you are unsure.
115
116config RCU_CPU_STALL_TIMEOUT
117 int "RCU CPU stall timeout in seconds"
118 depends on RCU_STALL_COMMON
119 range 3 300
120 default 21
121 help
122 If a given RCU grace period extends more than the specified
123 number of seconds, a CPU stall warning is printed. If the
124 RCU grace period persists, additional CPU stall warnings are
125 printed at more widely spaced intervals.
126
127config RCU_EXP_CPU_STALL_TIMEOUT
128 int "Expedited RCU CPU stall timeout in milliseconds"
129 depends on RCU_STALL_COMMON
130 range 0 300000
131 default 0
132 help
133 If a given expedited RCU grace period extends more than the
134 specified number of milliseconds, a CPU stall warning is printed.
135 If the RCU grace period persists, additional CPU stall warnings
136 are printed at more widely spaced intervals. A value of zero
137 says to use the RCU_CPU_STALL_TIMEOUT value converted from
138 seconds to milliseconds.
139
140config RCU_CPU_STALL_CPUTIME
141 bool "Provide additional RCU stall debug information"
142 depends on RCU_STALL_COMMON
143 default n
144 help
145 Collect statistics during the sampling period, such as the number of
146 (hard interrupts, soft interrupts, task switches) and the cputime of
147 (hard interrupts, soft interrupts, kernel tasks) are added to the
148 RCU stall report. For multiple continuous RCU stalls, all sampling
149 periods begin at half of the first RCU stall timeout.
150 The boot option rcupdate.rcu_cpu_stall_cputime has the same function
151 as this one, but will override this if it exists.
152
153config RCU_CPU_STALL_NOTIFIER
154 bool "Provide RCU CPU-stall notifiers"
155 depends on RCU_STALL_COMMON
156 depends on DEBUG_KERNEL
157 depends on RCU_EXPERT
158 default n
159 help
160 WARNING: You almost certainly do not want this!!!
161
162 Enable RCU CPU-stall notifiers, which are invoked just before
163 printing the RCU CPU stall warning. As such, bugs in notifier
164 callbacks can prevent stall warnings from being printed.
165 And the whole reason that a stall warning is being printed is
166 that something is hung up somewhere. Therefore, the notifier
167 callbacks must be written extremely carefully, preferably
168 containing only lockless code. After all, it is quite possible
169 that the whole reason that the RCU CPU stall is happening in
170 the first place is that someone forgot to release whatever lock
171 that you are thinking of acquiring. In which case, having your
172 notifier callback acquire that lock will hang, preventing the
173 RCU CPU stall warning from appearing.
174
175 Say Y here if you want RCU CPU stall notifiers (you don't want them)
176 Say N if you are unsure.
177
178config RCU_TRACE
179 bool "Enable tracing for RCU"
180 depends on DEBUG_KERNEL
181 default y if TREE_RCU
182 select TRACE_CLOCK
183 help
184 This option enables additional tracepoints for ftrace-style
185 event tracing.
186
187 Say Y here if you want to enable RCU tracing
188 Say N if you are unsure.
189
190config RCU_EQS_DEBUG
191 bool "Provide debugging asserts for adding NO_HZ support to an arch"
192 depends on DEBUG_KERNEL
193 help
194 This option provides consistency checks in RCU's handling of
195 NO_HZ. These checks have proven quite helpful in detecting
196 bugs in arch-specific NO_HZ code.
197
198 Say N here if you need ultimate kernel/user switch latencies
199 Say Y if you are unsure
200
201config RCU_STRICT_GRACE_PERIOD
202 bool "Provide debug RCU implementation with short grace periods"
203 depends on DEBUG_KERNEL && RCU_EXPERT && NR_CPUS <= 4 && !TINY_RCU
204 default n
205 select PREEMPT_COUNT if PREEMPT=n
206 help
207 Select this option to build an RCU variant that is strict about
208 grace periods, making them as short as it can. This limits
209 scalability, destroys real-time response, degrades battery
210 lifetime and kills performance. Don't try this on large
211 machines, as in systems with more than about 10 or 20 CPUs.
212 But in conjunction with tools like KASAN, it can be helpful
213 when looking for certain types of RCU usage bugs, for example,
214 too-short RCU read-side critical sections.
215
216
217config RCU_DYNTICKS_TORTURE
218 bool "Minimize RCU dynticks counter size"
219 depends on RCU_EXPERT && !COMPILE_TEST
220 default n
221 help
222 This option sets the width of the dynticks counter to its
223 minimum usable value. This minimum width greatly increases
224 the probability of flushing out bugs involving counter wrap,
225 but it also increases the probability of extending grace period
226 durations. This Kconfig option should therefore be avoided in
227 production due to the consequent increased probability of OOMs.
228
229 This has no value for production and is only for testing.
230
231config TRIVIAL_PREEMPT_RCU
232 bool "Textbook trivial preemptible RCU in rcutorture"
233 depends on RCU_EXPERT && RCU_TORTURE_TEST
234 default n
235 help
236 This option enables a textbook preemptible RCU that is
237 implemented in rcutorture. Its sole purpose is to validate
238 code used in books, papers, and presentations.
239
240 This has no value for production and is only for testing.
241
242endmenu # "RCU Debugging"