linux/kernel
Paul E. McKenney 7cb9249900 rcu: Permit dyntick-idle with callbacks pending
The current implementation of RCU_FAST_NO_HZ prevents CPUs from entering
dyntick-idle state if they have RCU callbacks pending.  Unfortunately,
this has the side-effect of often preventing them from entering this
state, especially if at least one other CPU is not in dyntick-idle state.
However, the resulting per-tick wakeup is wasteful in many cases: if the
CPU has already fully responded to the current RCU grace period, there
will be nothing for it to do until this grace period ends, which will
frequently take several jiffies.

This commit therefore permits a CPU that has done everything that the
current grace period has asked of it (rcu_pending() == 0) even if it
still as RCU callbacks pending.  However, such a CPU posts a timer to
wake it up several jiffies later (6 jiffies, based on experience with
grace-period lengths).  This wakeup is required to handle situations
that can result in all CPUs being in dyntick-idle mode, thus failing
to ever complete the current grace period.  If a CPU wakes up before
the timer goes off, then it cancels that timer, thus avoiding spurious
wakeups.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2011-12-11 10:32:07 -08:00
..
debug kdb: Make KDB use the new is_idle_task() API 2011-12-11 10:31:52 -08:00
events events: Make events use the new is_idle_task() API 2011-12-11 10:31:54 -08:00
gcov gcov: disable CONSTRUCTORS for UML 2011-07-26 16:49:45 -07:00
irq genirq: Fix race condition when stopping the irq thread 2011-12-02 11:54:24 +01:00
power PM / Hibernate: Do not leak memory in error/test code paths 2011-11-23 21:03:38 +01:00
time nohz: Remove tick_nohz_idle_enter_norcu() / tick_nohz_idle_exit_norcu() 2011-12-11 10:31:57 -08:00
trace trace: Allow ftrace_dump() to be called from modules 2011-12-11 10:31:25 -08:00
.gitignore
acct.c
async.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
audit_tree.c audit_tree,rcu: Convert call_rcu(__put_tree) to kfree_rcu() 2011-07-20 14:10:11 -07:00
audit_watch.c kill path_lookup() 2011-03-14 09:15:23 -04:00
audit.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
audit.h
auditfilter.c netlink: kill loginuid/sessionid/sid members from struct netlink_skb_parms 2011-03-03 10:55:40 -08:00
auditsc.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
backtracetest.c
bounds.c memcg: remove direct page_cgroup-to-page pointer 2011-03-23 19:46:28 -07:00
capability.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
cgroup_freezer.c cgroup_freezer: fix freezing groups with stopped tasks 2011-11-24 11:58:22 -08:00
cgroup.c memcg: replace ss->id_lock with a rwlock 2011-11-02 16:07:03 -07:00
compat.c kernel: Fix files explicitly needing EXPORT_SYMBOL infrastructure 2011-10-31 19:30:05 -04:00
configs.c kernel/configs.c: include MODULE_*() when CONFIG_IKCONFIG_PROC=n 2011-07-25 20:57:15 -07:00
cpu_pm.c cpu_pm: call notifiers during suspend 2011-09-23 12:05:29 +05:30
cpu.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
cpuset.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
crash_dump.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
cred.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
delayacct.c KVM: Steal time implementation 2011-07-14 12:59:14 +03:00
dma.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
elfcore.c
exec_domain.c
exit.c oom: remove oom_disable_count 2011-10-31 17:30:45 -07:00
extable.c extable, core_kernel_data(): Make sure all archs define _sdata 2011-05-20 08:56:56 +02:00
fork.c writeback: remove vm_dirties and task->dirties 2011-11-17 20:49:06 +08:00
freezer.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
futex_compat.c userns: user namespaces: convert several capable() calls 2011-03-23 19:47:08 -07:00
futex.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
groups.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
hrtimer.c Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2011-11-28 08:43:52 -08:00
hung_task.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
irq_work.c kernel: fix two implicit header assumptions in irq_work.c 2011-10-31 09:20:12 -04:00
itimer.c
jump_label.c jump_label: jump_label_inc may return before the code is patched 2011-12-05 13:28:46 -05:00
kallsyms.c Merge branch 'core-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip 2011-03-25 17:52:22 -07:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks arch:Kconfig.locks Remove unused config option. 2011-04-10 17:01:05 +02:00
Kconfig.preempt sched: Isolate preempt counting in its own config option 2011-06-10 15:15:40 +02:00
kexec.c [S390] kdump: Add infrastructure for unmapping crashkernel memory 2011-10-30 15:16:42 +01:00
kfifo.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
kmod.c kmod: prevent kmod_loop_msg overflow in __request_module() 2011-10-26 13:10:39 +10:30
kprobes.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
ksysfs.c kernel: ksysfs.c is implicitly using stat.h 2011-10-31 09:20:13 -04:00
kthread.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
latencytop.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
lockdep_internals.h
lockdep_proc.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
lockdep_states.h
lockdep.c rcu: Inform the user about extended quiescent state on PROVE_RCU warning 2011-12-11 10:31:30 -08:00
Makefile Merge branch 'devel-stable' of http://ftp.arm.linux.org.uk/pub/linux/arm/kernel/git-cur/linux-2.6-arm 2011-10-28 12:02:27 -07:00
module.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
mutex-debug.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mutex-debug.h mutex: Use p->on_cpu for the adaptive spin 2011-04-14 08:52:33 +02:00
mutex.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
mutex.h mutex: Use p->on_cpu for the adaptive spin 2011-04-14 08:52:33 +02:00
notifier.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
nsproxy.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
padata.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
panic.c module,bug: Add TAINT_OOT_MODULE flag for modules not built in-tree 2011-11-07 07:54:42 +10:30
params.c kernel: params.c needs module.h not moduleparam.h 2011-10-31 09:20:13 -04:00
pid_namespace.c pidns: call pid_ns_prepare_proc() from create_pid_namespace() 2011-03-23 19:46:58 -07:00
pid.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
posix-cpu-timers.c Merge branch 'core-locking-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2011-10-26 16:17:32 +02:00
posix-timers.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
printk.c printk: avoid double lock acquire 2011-12-09 07:50:28 -08:00
profile.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
ptrace.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
range.c range: fix bogus misuse of module.h to get printk() 2011-10-31 09:20:11 -04:00
rcu.h rcu: Deconfuse dynticks entry-exit tracing 2011-12-11 10:31:42 -08:00
rcupdate.c rcu: Detect illegal rcu dereference in extended quiescent state 2011-12-11 10:31:30 -08:00
rcutiny_plugin.h kernel: fix up module header handling in rcutiny files 2011-10-31 09:20:13 -04:00
rcutiny.c rcu: Make RCU use the new is_idle_task() API 2011-12-11 10:31:48 -08:00
rcutorture.c rcu: Add rcutorture CPU-hotplug capability 2011-12-11 10:31:56 -08:00
rcutree_plugin.h rcu: Permit dyntick-idle with callbacks pending 2011-12-11 10:32:07 -08:00
rcutree_trace.c rcu: Track idleness independent of idle tasks 2011-12-11 10:31:24 -08:00
rcutree.c rcu: Permit dyntick-idle with callbacks pending 2011-12-11 10:32:07 -08:00
rcutree.h rcu: Permit dyntick-idle with callbacks pending 2011-12-11 10:32:07 -08:00
relay.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
res_counter.c memcg: res_counter_read_u64(): fix potential races on 32-bit machines 2011-03-23 19:46:22 -07:00
resource.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
rtmutex_common.h rtmutex: Simplify PI algorithm and make highest prio task get lock 2011-01-27 21:13:51 -05:00
rtmutex-debug.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
rtmutex-debug.h
rtmutex-tester.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
rtmutex.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
rtmutex.h
rwsem.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
sched_autogroup.c Fix common misspellings 2011-03-31 11:26:23 -03:00
sched_autogroup.h sched: Skip autogroup when looking for all rt sched groups 2011-07-01 10:39:08 +02:00
sched_clock.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
sched_cpupri.c sched/cpupri: Remove cpupri->pri_active 2011-08-14 12:01:11 +02:00
sched_cpupri.h sched/cpupri: Remove cpupri->pri_active 2011-08-14 12:01:11 +02:00
sched_debug.c sched: Get rid of lock_depth 2011-04-24 13:18:38 +02:00
sched_fair.c sched: Fix buglet in return_cfs_rq_runtime() 2011-11-16 08:43:45 +01:00
sched_features.h sched, rt: Provide means of disabling cross-cpu bandwidth sharing 2011-11-14 12:50:40 +01:00
sched_idletask.c sched: Drop the rq argument to sched_class::select_task_rq() 2011-04-14 08:52:36 +02:00
sched_rt.c sched, rt: Provide means of disabling cross-cpu bandwidth sharing 2011-11-14 12:50:40 +01:00
sched_stats.h locking, sched: Annotate thread_group_cputimer as raw 2011-09-13 11:11:55 +02:00
sched_stoptask.c sched: Implement hierarchical task accounting for SCHED_OTHER 2011-08-14 12:01:13 +02:00
sched.c sched: Set the command name of the idle tasks in SMP kernels 2011-11-14 12:50:43 +01:00
seccomp.c
semaphore.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
signal.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
smp.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
softirq.c rcu: Fix early call to rcu_idle_enter() 2011-12-11 10:31:38 -08:00
spinlock.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
srcu.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
stacktrace.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
stop_machine.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
sys_ni.c Cross Memory Attach 2011-10-31 17:30:44 -07:00
sys.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
sysctl_binary.c ipv4: NET_IPV4_ROUTE_GC_INTERVAL removal 2011-10-03 14:13:01 -04:00
sysctl_check.c xfs: remove subdirectories 2011-08-12 16:21:35 -05:00
sysctl.c Merge branch 'akpm' (Andrew's incoming) 2011-10-31 17:46:07 -07:00
taskstats.c Make TASKSTATS require root access 2011-09-19 17:04:37 -07:00
test_kprobes.c
time.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
timeconst.pl
timer.c sys_getppid: add missing rcu_dereference 2011-12-09 07:50:29 -08:00
tracepoint.c Tracepoint: Dissociate from module mutex 2011-08-10 20:38:14 -04:00
tsacct.c Make taskstats round statistics down to nearest 1k bytes/events 2011-09-19 17:10:57 -07:00
uid16.c userns: user namespaces: convert several capable() calls 2011-03-23 19:47:08 -07:00
up.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user_namespace.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user-return-notifier.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
user.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
utsname_sysctl.c Merge branch 'modsplit-Oct31_2011' of git://git.kernel.org/pub/scm/linux/kernel/git/paulg/linux 2011-11-06 19:44:47 -08:00
utsname.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
wait.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00
watchdog.c watchdog: move watchdog_*_all_cpus under CONFIG_SYSCTL 2011-10-31 17:30:53 -07:00
workqueue_sched.h
workqueue.c kernel: Map most files to use export.h instead of module.h 2011-10-31 09:20:12 -04:00