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>

1 files changed, 1 insertions, 0 deletions

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() */