Paul E. McKenney ed93dfc6bc rcu: Confine ->core_needs_qs accesses to the corresponding CPU ... Commit 671a63517c ("rcu: Avoid unnecessary softirq when system is idle") fixed a bug that could result in an indefinite number of unnecessary invocations of the RCU_SOFTIRQ handler at the trailing edge of a scheduler-clock interrupt. However, the fix introduced off-CPU stores to ->core_needs_qs. These writes did not conflict with the on-CPU stores because the CPU's leaf rcu_node structure's ->lock was held across all such stores. However, the loads from ->core_needs_qs were not promoted to READ_ONCE() and, worse yet, the code loading from ->core_needs_qs was written assuming that it was only ever updated by the corresponding CPU. So operation has been robust, but only by luck. This situation is therefore an accident waiting to happen. This commit therefore takes a different approach. Instead of clearing ->core_needs_qs from the grace-period kthread's force-quiescent-state processing, it modifies the rcu_pending() function to suppress the rcu_sched_clock_irq() function's call to invoke_rcu_core() if there is no grace period in progress. This avoids the infinite needless RCU_SOFTIRQ handlers while still keeping all accesses to ->core_needs_qs local to the corresponding CPU. Signed-off-by: Paul E. McKenney <paulmck@kernel.org>		2019-10-28 07:02:21 -07:00
..
Kconfig	rcu: Use CONFIG_PREEMPTION	2019-07-31 19:03:35 +02:00
Kconfig.debug	rcu: Add support for consolidated-RCU reader checking	2019-08-09 11:00:35 -07:00
Makefile	License cleanup: add SPDX GPL-2.0 license identifier to files with no license	2017-11-02 11:10:55 +01:00
rcu_segcblist.c	rcu/nocb: Add bypass callback queueing	2019-08-13 14:37:32 -07:00
rcu_segcblist.h	rcu/nocb: Add bypass callback queueing	2019-08-13 14:37:32 -07:00
rcu.h	rcu: Add kernel parameter to dump trace after RCU CPU stall warning	2019-08-01 14:05:51 -07:00
rcuperf.c	rcuperf: Make rcuperf kernel test more robust for !expedited mode	2019-08-01 14:30:22 -07:00
rcutorture.c	rcutorture: Emulate dyntick aspect of userspace nohz_full sojourn	2019-10-05 10:46:05 -07:00
srcutiny.c	srcu: Remove cleanup_srcu_struct_quiesced()	2019-03-26 14:39:24 -07:00
srcutree.c	srcu: Avoid srcutorture security-based pointer obfuscation	2019-08-01 14:05:51 -07:00
sync.c	rcu/sync: Simplify the state machine	2019-05-28 09:05:23 -07:00
tiny.c	rcu: rcu_qs -- Use raise_softirq_irqoff to not save irqs twice	2019-03-26 14:37:49 -07:00
tree_exp.h	rcu: Fix spelling mistake "greate"->"great"	2019-08-12 11:25:06 -07:00
tree_plugin.h	rcu/nocb: Don't wake no-CBs GP kthread if timer posted under overload	2019-08-13 14:38:24 -07:00
tree_stall.h	Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2019-09-16 17:25:49 -07:00
tree.c	rcu: Confine ->core_needs_qs accesses to the corresponding CPU	2019-10-28 07:02:21 -07:00
tree.h	rcu: Force tick on for nohz_full CPUs not reaching quiescent states	2019-10-28 07:02:21 -07:00
update.c	Merge branches 'consolidate.2019.08.01b', 'fixes.2019.08.12a', 'lists.2019.08.13a' and 'torture.2019.08.01b' into HEAD	2019-08-13 14:30:30 -07:00