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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-07-25 11:21:47 -0700
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2014-09-16 10:07:59 -0700
commitf4579fc57cf4244057b713b1f73f4dc9f0b11e97 (patch)
tree7c682f8da323a07e5a6d63ad4ff87cc1baf34e73 /init
parent11ed7f934cb807f26da09547b5946c2e534d1dac (diff)
downloadlwn-f4579fc57cf4244057b713b1f73f4dc9f0b11e97.tar.gz
lwn-f4579fc57cf4244057b713b1f73f4dc9f0b11e97.zip
rcu: Fix attempt to avoid unsolicited offloading of callbacks
Commit b58cc46c5f6b (rcu: Don't offload callbacks unless specifically requested) failed to adjust the callback lists of the CPUs that are known to be no-CBs CPUs only because they are also nohz_full= CPUs. This failure can result in callbacks that are posted during early boot getting stranded on nxtlist for CPUs whose no-CBs property becomes apparent late, and there can also be spurious warnings about offline CPUs posting callbacks. This commit fixes these problems by adding an early-boot rcu_init_nohz() that properly initializes the no-CBs CPUs. Note that kernels built with CONFIG_RCU_NOCB_CPU_ALL=y or with CONFIG_RCU_NOCB_CPU=n do not exhibit this bug. Neither do kernels booted without the nohz_full= boot parameter. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Pranith Kumar <bobby.prani@gmail.com> Tested-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Diffstat (limited to 'init')
-rw-r--r--init/Kconfig4
-rw-r--r--init/main.c1
2 files changed, 3 insertions, 2 deletions
diff --git a/init/Kconfig b/init/Kconfig
index e84c6423a2e5..64ee4d967786 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -737,7 +737,7 @@ choice
config RCU_NOCB_CPU_NONE
bool "No build_forced no-CBs CPUs"
- depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL
+ depends on RCU_NOCB_CPU
help
This option does not force any of the CPUs to be no-CBs CPUs.
Only CPUs designated by the rcu_nocbs= boot parameter will be
@@ -751,7 +751,7 @@ config RCU_NOCB_CPU_NONE
config RCU_NOCB_CPU_ZERO
bool "CPU 0 is a build_forced no-CBs CPU"
- depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL
+ depends on RCU_NOCB_CPU
help
This option forces CPU 0 to be a no-CBs CPU, so that its RCU
callbacks are invoked by a per-CPU kthread whose name begins
diff --git a/init/main.c b/init/main.c
index bb1aed928f21..e3c4cdd94d5b 100644
--- a/init/main.c
+++ b/init/main.c
@@ -578,6 +578,7 @@ asmlinkage __visible void __init start_kernel(void)
idr_init_cache();
rcu_init();
tick_nohz_init();
+ rcu_init_nohz();
context_tracking_init();
radix_tree_init();
/* init some links before init_ISA_irqs() */