xref: /linux/kernel/rcu/Kconfig.debug (revision 06d07429858317ded2db7986113a9e0129cd599b)
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