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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-06-20 22:11:34 +0300
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2017-07-25 23:03:43 +0300
commita58163d8ca2c8d288ee9f95989712f98473a5ac2 (patch)
tree05bdf7b5403933bf4a45f93c841d3e98d6835f87 /include/linux/rcupdate.h
parent520eccdfe187591a51ea9ab4c1a024ae4d0f68d9 (diff)
downloadlinux-a58163d8ca2c8d288ee9f95989712f98473a5ac2.tar.xz
rcu: Migrate callbacks earlier in the CPU-offline timeline
RCU callbacks must be migrated away from an outgoing CPU, and this is done near the end of the CPU-hotplug operation, after the outgoing CPU is long gone. Unfortunately, this means that other CPU-hotplug callbacks can execute while the outgoing CPU's callbacks are still immobilized on the long-gone CPU's callback lists. If any of these CPU-hotplug callbacks must wait, either directly or indirectly, for the invocation of any of the immobilized RCU callbacks, the system will hang. This commit avoids such hangs by migrating the callbacks away from the outgoing CPU immediately upon its departure, shortly after the return from __cpu_die() in takedown_cpu(). Thus, RCU is able to advance these callbacks and invoke them, which allows all the after-the-fact CPU-hotplug callbacks to wait on these RCU callbacks without risk of a hang. While in the neighborhood, this commit also moves rcu_send_cbs_to_orphanage() and rcu_adopt_orphan_cbs() under a pre-existing #ifdef to avoid including dead code on the one hand and to avoid define-without-use warnings on the other hand. Reported-by: Jeffrey Hugo <jhugo@codeaurora.org> Link: http://lkml.kernel.org/r/db9c91f6-1b17-6136-84f0-03c3c2581ab4@codeaurora.org Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Anna-Maria Gleixner <anna-maria@linutronix.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Richard Weinberger <richard@nod.at>
Diffstat (limited to 'include/linux/rcupdate.h')
-rw-r--r--include/linux/rcupdate.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index f816fc72b51e..cf307ebf345d 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -110,6 +110,7 @@ void rcu_bh_qs(void);
void rcu_check_callbacks(int user);
void rcu_report_dead(unsigned int cpu);
void rcu_cpu_starting(unsigned int cpu);
+void rcutree_migrate_callbacks(int cpu);
#ifdef CONFIG_RCU_STALL_COMMON
void rcu_sysrq_start(void);