# 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. endmenu # "RCU Debugging"