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Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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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"