From 0f41c0ddadfb3d5baffe62351c380e2881aacd58 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 10 Mar 2015 18:33:20 -0700 Subject: rcu: Provide diagnostic option to slow down grace-period scans Grace-period scans of the rcu_node combining tree normally proceed quite quickly, so that it is very difficult to reproduce races against them. This commit therefore allows grace-period pre-initialization and cleanup to be artificially slowed down, increasing race-reproduction probability. A pair of pairs of new Kconfig parameters are provided, RCU_TORTURE_TEST_SLOW_PREINIT to enable the slowing down of propagating CPU-hotplug changes up the combining tree along with RCU_TORTURE_TEST_SLOW_PREINIT_DELAY to specify the delay in jiffies, and RCU_TORTURE_TEST_SLOW_CLEANUP to enable the slowing down of the end-of-grace-period cleanup scan along with RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY to specify the delay in jiffies. Boot-time parameters named rcutree.gp_preinit_delay and rcutree.gp_cleanup_delay allow these delays to be specified at boot time. Signed-off-by: Paul E. McKenney --- lib/Kconfig.debug | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 52 insertions(+), 2 deletions(-) (limited to 'lib') diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index ba2b0c87e65b..e1af93ae246b 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1261,12 +1261,38 @@ config RCU_TORTURE_TEST_RUNNABLE Say N here if you want the RCU torture tests to start only after being manually enabled via /proc. +config RCU_TORTURE_TEST_SLOW_PREINIT + bool "Slow down RCU grace-period pre-initialization to expose races" + depends on RCU_TORTURE_TEST + help + This option delays grace-period pre-initialization (the + propagation of CPU-hotplug changes up the rcu_node combining + tree) for a few jiffies between initializing each pair of + consecutive rcu_node structures. This helps to expose races + involving grace-period pre-initialization, in other words, it + makes your kernel less stable. It can also greatly increase + grace-period latency, especially on systems with large numbers + of CPUs. This is useful when torture-testing RCU, but in + almost no other circumstance. + + Say Y here if you want your system to crash and hang more often. + Say N if you want a sane system. + +config RCU_TORTURE_TEST_SLOW_PREINIT_DELAY + int "How much to slow down RCU grace-period pre-initialization" + range 0 5 + default 3 + depends on RCU_TORTURE_TEST_SLOW_PREINIT + help + This option specifies the number of jiffies to wait between + each rcu_node structure pre-initialization step. + config RCU_TORTURE_TEST_SLOW_INIT bool "Slow down RCU grace-period initialization to expose races" depends on RCU_TORTURE_TEST help - This option makes grace-period initialization block for a - few jiffies between initializing each pair of consecutive + This option delays grace-period initialization for a few + jiffies between initializing each pair of consecutive rcu_node structures. This helps to expose races involving grace-period initialization, in other words, it makes your kernel less stable. It can also greatly increase grace-period @@ -1286,6 +1312,30 @@ config RCU_TORTURE_TEST_SLOW_INIT_DELAY This option specifies the number of jiffies to wait between each rcu_node structure initialization. +config RCU_TORTURE_TEST_SLOW_CLEANUP + bool "Slow down RCU grace-period cleanup to expose races" + depends on RCU_TORTURE_TEST + help + This option delays grace-period cleanup for a few jiffies + between cleaning up each pair of consecutive rcu_node + structures. This helps to expose races involving grace-period + cleanup, in other words, it makes your kernel less stable. + It can also greatly increase grace-period latency, especially + on systems with large numbers of CPUs. This is useful when + torture-testing RCU, but in almost no other circumstance. + + Say Y here if you want your system to crash and hang more often. + Say N if you want a sane system. + +config RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY + int "How much to slow down RCU grace-period cleanup" + range 0 5 + default 3 + depends on RCU_TORTURE_TEST_SLOW_CLEANUP + help + This option specifies the number of jiffies to wait between + each rcu_node structure cleanup operation. + config RCU_CPU_STALL_TIMEOUT int "RCU CPU stall timeout in seconds" depends on RCU_STALL_COMMON -- cgit v1.2.3-59-g8ed1b