kernel/rcu/Kconfig.debug - linux - Git at Google


            
            # SPDX-License-Identifier: GPL-2.0-only

            
            #

            
            # RCU-related debugging configuration options

            
            #


            menu "RCU Debugging"


            config PROVE_RCU

            
            	def_bool PROVE_LOCKING


            config PROVE_RCU_LIST

            
            	bool "RCU list lockdep debugging"

            
            	depends on PROVE_RCU && RCU_EXPERT

            
            	default n

            
            	help

            
            	  Enable RCU lockdep checking for list usages. By default it is

            
            	  turned off since there are several list RCU users that still

            
            	  need to be converted to pass a lockdep expression. To prevent

            
            	  false-positive splats, we keep it default disabled but once all

            
            	  users are converted, we can remove this config option.


            config TORTURE_TEST

            
            	tristate

            
            	default n


            config RCU_SCALE_TEST

            
            	tristate "performance tests for RCU"

            
            	depends on DEBUG_KERNEL

            
            	select TORTURE_TEST

            
            	default n

            
            	help

            
            	  This option provides a kernel module that runs performance

            
            	  tests on the RCU infrastructure.  The kernel module may be built

            
            	  after the fact on the running kernel to be tested, if desired.


            	  Say Y here if you want RCU performance tests to be built into

            
            	  the kernel.

            
            	  Say M if you want the RCU performance tests to build as a module.

            
            	  Say N if you are unsure.


            config RCU_TORTURE_TEST

            
            	tristate "torture tests for RCU"

            
            	depends on DEBUG_KERNEL

            
            	select TORTURE_TEST

            
            	default n

            
            	help

            
            	  This option provides a kernel module that runs torture tests

            
            	  on the RCU infrastructure.  The kernel module may be built

            
            	  after the fact on the running kernel to be tested, if desired.


            	  Say Y here if you want RCU torture tests to be built into

            
            	  the kernel.

            
            	  Say M if you want the RCU torture tests to build as a module.

            
            	  Say N if you are unsure.


            config RCU_TORTURE_TEST_CHK_RDR_STATE

            
            	bool "Check rcutorture reader state"

            
            	depends on RCU_TORTURE_TEST

            
            	default n

            
            	help

            
            	  This option causes rcutorture to check the desired rcutorture

            
            	  reader state for each segment against the actual context.

            
            	  Note that PREEMPT_COUNT must be enabled if the preempt-disabled

            
            	  and bh-disabled checks are to take effect, and that PREEMPT_RCU

            
            	  must be enabled for the RCU-nesting checks to take effect.

            
            	  These checks add overhead, and this Kconfig options is therefore

            
            	  disabled by default.


            	  Say Y here if you want rcutorture reader contexts checked.

            
            	  Say N if you are unsure.


            config RCU_TORTURE_TEST_LOG_CPU

            
            	bool "Log CPU for rcutorture failures"

            
            	depends on RCU_TORTURE_TEST

            
            	default n

            
            	help

            
            	  This option causes rcutorture to decorate each entry of its

            
            	  log of failure/close-call rcutorture reader segments with the

            
            	  number of the CPU that the reader was running on at the time.

            
            	  This information can be useful, but it does incur additional

            
            	  overhead, overhead that can make both failures and close calls

            
            	  less probable.


            	  Say Y here if you want CPU IDs logged.

            
            	  Say N if you are unsure.


            config RCU_TORTURE_TEST_LOG_GP

            
            	bool "Log grace-period numbers for rcutorture failures"

            
            	depends on RCU_TORTURE_TEST

            
            	default n

            
            	help

            
            	  This option causes rcutorture to decorate each entry of its

            
            	  log of failure/close-call rcutorture reader segments with the

            
            	  corresponding grace-period sequence numbers.	This information

            
            	  can be useful, but it does incur additional overhead, overhead

            
            	  that can make both failures and close calls less probable.


            	  Say Y here if you want grace-period sequence numbers logged.

            
            	  Say N if you are unsure.


            config RCU_REF_SCALE_TEST

            
            	tristate "Scalability tests for read-side synchronization (RCU and others)"

            
            	depends on DEBUG_KERNEL

            
            	select TORTURE_TEST

            
            	default n

            
            	help

            
            	  This option provides a kernel module that runs performance tests

            
            	  useful comparing RCU with various read-side synchronization mechanisms.

            
            	  The kernel module may be built after the fact on the running kernel to be

            
            	  tested, if desired.


            	  Say Y here if you want these performance tests built into the kernel.

            
            	  Say M if you want to build it as a module instead.

            
            	  Say N if you are unsure.


            config RCU_CPU_STALL_TIMEOUT

            
            	int "RCU CPU stall timeout in seconds"

            
            	depends on RCU_STALL_COMMON

            
            	range 3 300

            
            	default 21

            
            	help

            
            	  If a given RCU grace period extends more than the specified

            
            	  number of seconds, a CPU stall warning is printed.  If the

            
            	  RCU grace period persists, additional CPU stall warnings are

            
            	  printed at more widely spaced intervals.


            config RCU_EXP_CPU_STALL_TIMEOUT

            
            	int "Expedited RCU CPU stall timeout in milliseconds"

            
            	depends on RCU_STALL_COMMON

            
            	range 0 300000

            
            	default 0

            
            	help

            
            	  If a given expedited RCU grace period extends more than the

            
            	  specified number of milliseconds, a CPU stall warning is printed.

            
            	  If the RCU grace period persists, additional CPU stall warnings

            
            	  are printed at more widely spaced intervals.  A value of zero

            
            	  says to use the RCU_CPU_STALL_TIMEOUT value converted from

            
            	  seconds to milliseconds.


            config RCU_CPU_STALL_CPUTIME

            
            	bool "Provide additional RCU stall debug information"

            
            	depends on RCU_STALL_COMMON

            
            	default n

            
            	help

            
            	  Collect statistics during the sampling period, such as the number of

            
            	  (hard interrupts, soft interrupts, task switches) and the cputime of

            
            	  (hard interrupts, soft interrupts, kernel tasks) are added to the

            
            	  RCU stall report. For multiple continuous RCU stalls, all sampling

            
            	  periods begin at half of the first RCU stall timeout.

            
            	  The boot option rcupdate.rcu_cpu_stall_cputime has the same function

            
            	  as this one, but will override this if it exists.


            config RCU_CPU_STALL_NOTIFIER

            
            	bool "Provide RCU CPU-stall notifiers"

            
            	depends on RCU_STALL_COMMON

            
            	depends on DEBUG_KERNEL

            
            	depends on RCU_EXPERT

            
            	default n

            
            	help

            
            	  WARNING:  You almost certainly do not want this!!!


            	  Enable RCU CPU-stall notifiers, which are invoked just before

            
            	  printing the RCU CPU stall warning.  As such, bugs in notifier

            
            	  callbacks can prevent stall warnings from being printed.

            
            	  And the whole reason that a stall warning is being printed is

            
            	  that something is hung up somewhere.	Therefore, the notifier

            
            	  callbacks must be written extremely carefully, preferably

            
            	  containing only lockless code.  After all, it is quite possible

            
            	  that the whole reason that the RCU CPU stall is happening in

            
            	  the first place is that someone forgot to release whatever lock

            
            	  that you are thinking of acquiring.  In which case, having your

            
            	  notifier callback acquire that lock will hang, preventing the

            
            	  RCU CPU stall warning from appearing.


            	  Say Y here if you want RCU CPU stall notifiers (you don't want them)

            
            	  Say N if you are unsure.


            config RCU_TRACE

            
            	bool "Enable tracing for RCU"

            
            	depends on DEBUG_KERNEL

            
            	default y if TREE_RCU

            
            	select TRACE_CLOCK

            
            	help

            
            	  This option enables additional tracepoints for ftrace-style

            
            	  event tracing.


            	  Say Y here if you want to enable RCU tracing

            
            	  Say N if you are unsure.


            config RCU_EQS_DEBUG

            
            	bool "Provide debugging asserts for adding NO_HZ support to an arch"

            
            	depends on DEBUG_KERNEL

            
            	help

            
            	  This option provides consistency checks in RCU's handling of

            
            	  NO_HZ.  These checks have proven quite helpful in detecting

            
            	  bugs in arch-specific NO_HZ code.


            	  Say N here if you need ultimate kernel/user switch latencies

            
            	  Say Y if you are unsure


            config RCU_STRICT_GRACE_PERIOD

            
            	bool "Provide debug RCU implementation with short grace periods"

            
            	depends on DEBUG_KERNEL && RCU_EXPERT && NR_CPUS <= 4 && !TINY_RCU

            
            	default n

            
            	select PREEMPT_COUNT if PREEMPT=n

            
            	help

            
            	  Select this option to build an RCU variant that is strict about

            
            	  grace periods, making them as short as it can.  This limits

            
            	  scalability, destroys real-time response, degrades battery

            
            	  lifetime and kills performance.  Don't try this on large

            
            	  machines, as in systems with more than about 10 or 20 CPUs.

            
            	  But in conjunction with tools like KASAN, it can be helpful

            
            	  when looking for certain types of RCU usage bugs, for example,

            
            	  too-short RCU read-side critical sections.


            config RCU_DYNTICKS_TORTURE

            
            	bool "Minimize RCU dynticks counter size"

            
            	depends on RCU_EXPERT && !COMPILE_TEST

            
            	default n

            
            	help

            
            	  This option sets the width of the dynticks counter to its

            
            	  minimum usable value.  This minimum width greatly increases

            
            	  the probability of flushing out bugs involving counter wrap,

            
            	  but it also increases the probability of extending grace period

            
            	  durations.  This Kconfig option should therefore be avoided in

            
            	  production due to the consequent increased probability of OOMs.


            	  This has no value for production and is only for testing.


            config TRIVIAL_PREEMPT_RCU

            
            	bool "Textbook trivial preemptible RCU in rcutorture"

            
            	depends on RCU_EXPERT && RCU_TORTURE_TEST

            
            	default n

            
            	help

            
            	  This option enables a textbook preemptible RCU that is

            
            	  implemented in rcutorture.  Its sole purpose is to validate

            
            	  code used in books, papers, and presentations.


            	  This has no value for production and is only for testing.


            endmenu # "RCU Debugging"
	# SPDX-License-Identifier: GPL-2.0-only
	#
	# RCU-related debugging configuration options
	#

	menu "RCU Debugging"

	config PROVE_RCU
	def_bool PROVE_LOCKING

	config PROVE_RCU_LIST
	bool "RCU list lockdep debugging"
	depends on PROVE_RCU && RCU_EXPERT
	default n
	help
	Enable RCU lockdep checking for list usages. By default it is
	turned off since there are several list RCU users that still
	need to be converted to pass a lockdep expression. To prevent
	false-positive splats, we keep it default disabled but once all
	users are converted, we can remove this config option.

	config TORTURE_TEST
	tristate
	default n

	config RCU_SCALE_TEST
	tristate "performance tests for RCU"
	depends on DEBUG_KERNEL
	select TORTURE_TEST
	default n
	help
	This option provides a kernel module that runs performance
	tests on the RCU infrastructure. The kernel module may be built
	after the fact on the running kernel to be tested, if desired.

	Say Y here if you want RCU performance tests to be built into
	the kernel.
	Say M if you want the RCU performance tests to build as a module.
	Say N if you are unsure.

	config RCU_TORTURE_TEST
	tristate "torture tests for RCU"
	depends on DEBUG_KERNEL
	select TORTURE_TEST
	default n
	help
	This option provides a kernel module that runs torture tests
	on the RCU infrastructure. The kernel module may be built
	after the fact on the running kernel to be tested, if desired.

	Say Y here if you want RCU torture tests to be built into
	the kernel.
	Say M if you want the RCU torture tests to build as a module.
	Say N if you are unsure.

	config RCU_TORTURE_TEST_CHK_RDR_STATE
	bool "Check rcutorture reader state"
	depends on RCU_TORTURE_TEST
	default n
	help
	This option causes rcutorture to check the desired rcutorture
	reader state for each segment against the actual context.
	Note that PREEMPT_COUNT must be enabled if the preempt-disabled
	and bh-disabled checks are to take effect, and that PREEMPT_RCU
	must be enabled for the RCU-nesting checks to take effect.
	These checks add overhead, and this Kconfig options is therefore
	disabled by default.

	Say Y here if you want rcutorture reader contexts checked.
	Say N if you are unsure.

	config RCU_TORTURE_TEST_LOG_CPU
	bool "Log CPU for rcutorture failures"
	depends on RCU_TORTURE_TEST
	default n
	help
	This option causes rcutorture to decorate each entry of its
	log of failure/close-call rcutorture reader segments with the
	number of the CPU that the reader was running on at the time.
	This information can be useful, but it does incur additional
	overhead, overhead that can make both failures and close calls
	less probable.

	Say Y here if you want CPU IDs logged.
	Say N if you are unsure.

	config RCU_TORTURE_TEST_LOG_GP
	bool "Log grace-period numbers for rcutorture failures"
	depends on RCU_TORTURE_TEST
	default n
	help
	This option causes rcutorture to decorate each entry of its
	log of failure/close-call rcutorture reader segments with the
	corresponding grace-period sequence numbers. This information
	can be useful, but it does incur additional overhead, overhead
	that can make both failures and close calls less probable.

	Say Y here if you want grace-period sequence numbers logged.
	Say N if you are unsure.

	config RCU_REF_SCALE_TEST
	tristate "Scalability tests for read-side synchronization (RCU and others)"
	depends on DEBUG_KERNEL
	select TORTURE_TEST
	default n
	help
	This option provides a kernel module that runs performance tests
	useful comparing RCU with various read-side synchronization mechanisms.
	The kernel module may be built after the fact on the running kernel to be
	tested, if desired.

	Say Y here if you want these performance tests built into the kernel.
	Say M if you want to build it as a module instead.
	Say N if you are unsure.

	config RCU_CPU_STALL_TIMEOUT
	int "RCU CPU stall timeout in seconds"
	depends on RCU_STALL_COMMON
	range 3 300
	default 21
	help
	If a given RCU grace period extends more than the specified
	number of seconds, a CPU stall warning is printed. If the
	RCU grace period persists, additional CPU stall warnings are
	printed at more widely spaced intervals.

	config RCU_EXP_CPU_STALL_TIMEOUT
	int "Expedited RCU CPU stall timeout in milliseconds"
	depends on RCU_STALL_COMMON
	range 0 300000
	default 0
	help
	If a given expedited RCU grace period extends more than the
	specified number of milliseconds, a CPU stall warning is printed.
	If the RCU grace period persists, additional CPU stall warnings
	are printed at more widely spaced intervals. A value of zero
	says to use the RCU_CPU_STALL_TIMEOUT value converted from
	seconds to milliseconds.

	config RCU_CPU_STALL_CPUTIME
	bool "Provide additional RCU stall debug information"
	depends on RCU_STALL_COMMON
	default n
	help
	Collect statistics during the sampling period, such as the number of
	(hard interrupts, soft interrupts, task switches) and the cputime of
	(hard interrupts, soft interrupts, kernel tasks) are added to the
	RCU stall report. For multiple continuous RCU stalls, all sampling
	periods begin at half of the first RCU stall timeout.
	The boot option rcupdate.rcu_cpu_stall_cputime has the same function
	as this one, but will override this if it exists.

	config RCU_CPU_STALL_NOTIFIER
	bool "Provide RCU CPU-stall notifiers"
	depends on RCU_STALL_COMMON
	depends on DEBUG_KERNEL
	depends on RCU_EXPERT
	default n
	help
	WARNING: You almost certainly do not want this!!!

	Enable RCU CPU-stall notifiers, which are invoked just before
	printing the RCU CPU stall warning. As such, bugs in notifier
	callbacks can prevent stall warnings from being printed.
	And the whole reason that a stall warning is being printed is
	that something is hung up somewhere. Therefore, the notifier
	callbacks must be written extremely carefully, preferably
	containing only lockless code. After all, it is quite possible
	that the whole reason that the RCU CPU stall is happening in
	the first place is that someone forgot to release whatever lock
	that you are thinking of acquiring. In which case, having your
	notifier callback acquire that lock will hang, preventing the
	RCU CPU stall warning from appearing.

	Say Y here if you want RCU CPU stall notifiers (you don't want them)
	Say N if you are unsure.

	config RCU_TRACE
	bool "Enable tracing for RCU"
	depends on DEBUG_KERNEL
	default y if TREE_RCU
	select TRACE_CLOCK
	help
	This option enables additional tracepoints for ftrace-style
	event tracing.

	Say Y here if you want to enable RCU tracing
	Say N if you are unsure.

	config RCU_EQS_DEBUG
	bool "Provide debugging asserts for adding NO_HZ support to an arch"
	depends on DEBUG_KERNEL
	help
	This option provides consistency checks in RCU's handling of
	NO_HZ. These checks have proven quite helpful in detecting
	bugs in arch-specific NO_HZ code.

	Say N here if you need ultimate kernel/user switch latencies
	Say Y if you are unsure

	config RCU_STRICT_GRACE_PERIOD
	bool "Provide debug RCU implementation with short grace periods"
	depends on DEBUG_KERNEL && RCU_EXPERT && NR_CPUS <= 4 && !TINY_RCU
	default n
	select PREEMPT_COUNT if PREEMPT=n
	help
	Select this option to build an RCU variant that is strict about
	grace periods, making them as short as it can. This limits
	scalability, destroys real-time response, degrades battery
	lifetime and kills performance. Don't try this on large
	machines, as in systems with more than about 10 or 20 CPUs.
	But in conjunction with tools like KASAN, it can be helpful
	when looking for certain types of RCU usage bugs, for example,
	too-short RCU read-side critical sections.


	config RCU_DYNTICKS_TORTURE
	bool "Minimize RCU dynticks counter size"
	depends on RCU_EXPERT && !COMPILE_TEST
	default n
	help
	This option sets the width of the dynticks counter to its
	minimum usable value. This minimum width greatly increases
	the probability of flushing out bugs involving counter wrap,
	but it also increases the probability of extending grace period
	durations. This Kconfig option should therefore be avoided in
	production due to the consequent increased probability of OOMs.

	This has no value for production and is only for testing.

	config TRIVIAL_PREEMPT_RCU
	bool "Textbook trivial preemptible RCU in rcutorture"
	depends on RCU_EXPERT && RCU_TORTURE_TEST
	default n
	help
	This option enables a textbook preemptible RCU that is
	implemented in rcutorture. Its sole purpose is to validate
	code used in books, papers, and presentations.

	This has no value for production and is only for testing.

	endmenu # "RCU Debugging"