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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-04-14 19:33:59 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2015-04-14 19:33:59 -0700
commit8d7dc9283f399e1fda4e48a1c453f689326d9396 (patch)
treec63e3a78f675521d36c032319c26e9f85f942f20 /lib
parent590ee7dbd569a012df705a5204fc5f1066f52b8c (diff)
downloadlinux-8d7dc9283f399e1fda4e48a1c453f689326d9396.tar.bz2
rcu: Control grace-period delays directly from value
In a misguided attempt to avoid an #ifdef, the use of the gp_init_delay module parameter was conditioned on the corresponding RCU_TORTURE_TEST_SLOW_INIT Kconfig variable, using IS_ENABLED() at the point of use in the code. This meant that the compiler always saw the delay, which meant that RCU_TORTURE_TEST_SLOW_INIT_DELAY had to be unconditionally defined. This in turn caused "make oldconfig" to ask pointless questions about the value of RCU_TORTURE_TEST_SLOW_INIT_DELAY in cases where it was not even used. This commit avoids these pointless questions by defining gp_init_delay under #ifdef. In one branch, gp_init_delay is initialized to RCU_TORTURE_TEST_SLOW_INIT_DELAY and is also a module parameter (thus allowing boot-time modification), and in the other branch gp_init_delay is a const variable initialized by default to zero. This approach also simplifies the code at the delay point by eliminating the IS_DEFINED(). Because gp_init_delay is constant zero in the no-delay case intended for production use, the "gp_init_delay > 0" check causes the delay to become dead code, as desired in this case. In addition, this commit replaces magic constant "10" with the preprocessor variable PER_RCU_NODE_PERIOD, which controls the number of grace periods that are allowed to elapse at full speed before a delay is inserted. Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug1
1 files changed, 1 insertions, 0 deletions
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1ad74c0df01f..5f5ff7d7e5eb 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1268,6 +1268,7 @@ config RCU_TORTURE_TEST_SLOW_INIT_DELAY
int "How much to slow down RCU grace-period initialization"
range 0 5
default 3
+ depends on RCU_TORTURE_TEST_SLOW_INIT
help
This option specifies the number of jiffies to wait between
each rcu_node structure initialization.