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rcu: Fix attempt to avoid unsolicited offloading of callbacks

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Commit b58cc46c5f (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>
This commit is contained in:
Paul E. McKenney
2014-07-25 11:21:47 -07:00
parent 11ed7f934c
commit f4579fc57c
4 changed files with 72 additions and 33 deletions
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init/main.c
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@@ -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() */