Paul E. McKenney d19fb8d1f3 rcu: Don't migrate blocked tasks even if all corresponding CPUs offline ... When the last CPU associated with a given leaf rcu_node structure goes offline, something must be done about the tasks queued on that rcu_node structure. Each of these tasks has been preempted on one of the leaf rcu_node structure's CPUs while in an RCU read-side critical section that it have not yet exited. Handling these tasks is the job of rcu_preempt_offline_tasks(), which migrates them from the leaf rcu_node structure to the root rcu_node structure. Unfortunately, this migration has to be done one task at a time because each tasks allegiance must be shifted from the original leaf rcu_node to the root, so that future attempts to deal with these tasks will acquire the root rcu_node structure's ->lock rather than that of the leaf. Worse yet, this migration must be done with interrupts disabled, which is not so good for realtime response, especially given that there is no bound on the number of tasks on a given rcu_node structure's list. (OK, OK, there is a bound, it is just that it is unreasonably large, especially on 64-bit systems.) This was not considered a problem back when rcu_preempt_offline_tasks() was first written because realtime systems were assumed not to do CPU-hotplug operations while real-time applications were running. This assumption has proved of dubious validity given that people are starting to run multiple realtime applications on a single SMP system and that it is common practice to offline then online a CPU before starting its real-time application in order to clear extraneous processing off of that CPU. So we now need CPU hotplug operations to avoid undue latencies. This commit therefore avoids migrating these tasks, instead letting them be dequeued one by one from the original leaf rcu_node structure by rcu_read_unlock_special(). This means that the clearing of bits from the upper-level rcu_node structures must be deferred until the last such task has been dequeued, because otherwise subsequent grace periods won't wait on them. This commit has the beneficial side effect of simplifying the CPU-hotplug code for TREE_PREEMPT_RCU, especially in CONFIG_RCU_BOOST builds. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>		2015-01-06 11:02:44 -08:00
..
bpf	bpf: verifier: add checks for BPF_ABS | BPF_IND instructions	2014-12-05 21:47:32 -08:00
configs	x86: Add "make tinyconfig" to configure the tiniest possible kernel	2014-08-08 16:30:24 -07:00
debug	kdb: replace strnicmp with strncasecmp	2014-10-14 02:18:25 +02:00
events	Merge branch 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-12-19 13:15:24 -08:00
gcov	gcov: enable GCOV_PROFILE_ALL from ARCH Kconfigs	2014-12-13 12:42:51 -08:00
irq	genirq: Prevent proc race against freeing of irq descriptors	2014-12-13 13:33:07 +01:00
locking	locking/mutex: Don't assume TASK_RUNNING	2014-10-28 10:55:08 +01:00
power	PM: Eliminate CONFIG_PM_RUNTIME	2014-12-19 22:55:06 +01:00
printk	This code is a fork from the trace-3.19 pull as it needed the trace_seq	2014-12-13 14:04:41 -08:00
rcu	rcu: Don't migrate blocked tasks even if all corresponding CPUs offline	2015-01-06 11:02:44 -08:00
sched	sched_show_task: fix unsafe usage of ->real_parent	2014-12-10 17:41:09 -08:00
time	Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-12-19 13:29:20 -08:00
trace	More ACPI and power management updates for 3.19-rc1	2014-12-18 20:28:33 -08:00
.gitignore	Ignore generated file kernel/x509_certificate_list	2013-12-10 18:21:34 +00:00
Kconfig.freezer	…
Kconfig.hz	…
Kconfig.locks	locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER	2014-07-16 14:57:13 +02:00
Kconfig.preempt	…
Makefile	kernel: res_counter: remove the unused API	2014-12-10 17:41:04 -08:00
acct.c	acct: eliminate compile warning	2014-10-09 22:26:04 -04:00
async.c	kernel/async.c: switch to pr_foo()	2014-10-09 22:26:04 -04:00
audit.c	Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit	2014-12-13 13:41:28 -08:00
audit.h	audit: reduce scope of audit_log_fcaps	2014-09-23 16:37:51 -04:00
audit_tree.c	fsnotify: unify inode and mount marks handling	2014-12-13 12:42:53 -08:00
audit_watch.c	audit: invalid op= values for rules	2014-09-23 16:37:53 -04:00
auditfilter.c	Merge git://git.infradead.org/users/eparis/audit	2014-10-19 16:25:56 -07:00
auditsc.c	new helper: audit_file()	2014-11-19 13:01:26 -05:00
backtracetest.c	kernel/backtracetest.c: replace no level printk by pr_info()	2014-06-04 16:54:14 -07:00
bounds.c	page-cgroup: get rid of NR_PCG_FLAGS	2014-08-08 15:57:18 -07:00
capability.c	CAPABILITIES: remove undefined caps from all processes	2014-07-24 21:53:47 +10:00
cgroup.c	cgroup: implement cgroup_get_e_css()	2014-11-18 02:49:52 -05:00
cgroup_freezer.c	cgroup: rename cgroup_subsys->base_cftypes to ->legacy_cftypes	2014-07-15 11:05:09 -04:00
compat.c	compat: nanosleep: Clarify error handling	2014-09-06 12:58:18 +02:00
configs.c	…
context_tracking.c	sched: stop the unbound recursion in preempt_schedule_context()	2014-10-28 10:46:05 +01:00
cpu.c	cpu: Avoid puts_pending overflow	2014-11-03 19:21:01 -08:00
cpu_pm.c	…
cpuset.c	Merge branch 'for-3.19' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup	2014-12-11 18:57:19 -08:00
crash_dump.c	crash_dump: Make is_kdump_kernel() accessible from modules	2014-08-25 15:42:19 -07:00
cred.c	…
delayacct.c	delayacct: Remove braindamaged type conversions	2014-07-23 10:18:06 -07:00
dma.c	…
elfcore.c	…
exec_domain.c	kernel/exec_domain.c: code clean-up	2014-06-04 16:54:15 -07:00
exit.c	TTY/Serial driver patches for 3.19-rc1	2014-12-14 15:23:32 -08:00
extable.c	ftrace/x86/extable: Add is_ftrace_trampoline() function	2014-11-19 15:25:26 -05:00
fork.c	mm: use new helper functions around the i_mmap_mutex	2014-12-13 12:42:45 -08:00
freezer.c	freezer: remove obsolete comments in __thaw_task()	2014-10-21 23:44:20 +02:00
futex.c	futex: Fix a race condition between REQUEUE_PI and task death	2014-10-26 16:16:18 +01:00
futex_compat.c	compat: Get rid of (get|put)_compat_time(val|spec)	2014-02-02 14:09:12 -08:00
groups.c	userns: Don't allow setgroups until a gid mapping has been setablished	2014-12-09 16:58:40 -06:00
hung_task.c	kernel/hung_task.c: convert simple_strtoul to kstrtouint	2014-06-04 16:54:15 -07:00
irq_work.c	percpu: Convert remaining __get_cpu_var uses in 3.18-rcX	2014-10-29 11:18:18 -04:00
jump_label.c	…
kallsyms.c	kernel/kallsyms.c: use __seq_open_private()	2014-10-14 02:18:16 +02:00
kcmp.c	kcmp: fix standard comparison bug	2014-09-10 15:42:12 -07:00
kexec.c	kexec: remove unnecessary KERN_ERR from kexec.c	2014-12-13 12:42:51 -08:00
kmod.c	usermodehelper: kill the kmod_thread_locker logic	2014-12-10 17:41:17 -08:00
kprobes.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux	2014-12-11 17:30:55 -08:00
ksysfs.c	kobject: Make support for uevent_helper optional.	2014-04-25 12:00:49 -07:00
kthread.c	kernel/kthread.c: partial revert of 81c98869fa ("kthread: ensure locality of task_struct allocations")	2014-10-09 22:25:51 -04:00
latencytop.c	kernel/latencytop.c: convert seq_printf to seq_puts	2014-06-04 16:54:15 -07:00
module-internal.h	…
module.c	The exciting thing here is the getting rid of stop_machine on module	2014-12-18 20:55:41 -08:00
module_signing.c	…
notifier.c	kprobes, notifier: Use NOKPROBE_SYMBOL macro in notifier	2014-04-24 10:26:39 +02:00
nsproxy.c	bury struct proc_ns in fs/proc	2014-12-04 14:34:54 -05:00
padata.c	padata: Fix wrong usage of rcu_dereference()	2013-12-05 21:28:42 +08:00
panic.c	kernel: add panic_on_warn	2014-12-10 17:41:10 -08:00
params.c	param: do not set store func without write perm	2014-12-18 12:38:51 +10:30
pid.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2014-12-16 15:53:03 -08:00
pid_namespace.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2014-12-16 15:53:03 -08:00
profile.c	kernel/profile.c: use static const char instead of static char	2014-06-06 16:08:13 -07:00
ptrace.c	exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent()	2014-12-10 17:41:10 -08:00
range.c	…
reboot.c	kernel: add support for kernel restart handler call chain	2014-09-26 00:00:06 -07:00
relay.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2014-04-12 14:49:50 -07:00
resource.c	x86: optimize resource lookups for ioremap	2014-10-14 02:18:22 +02:00
seccomp.c	Merge branch 'x86-seccomp-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-10-14 02:27:06 +02:00
signal.c	Merge branch 'x86-mpx-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2014-12-10 09:34:43 -08:00
smp.c	Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu	2014-10-15 07:48:18 +02:00
smpboot.c	sched, smp: Correctly deal with nested sleeps	2014-10-28 10:56:24 +01:00
smpboot.h	…
softirq.c	rcu: Remove "cpu" argument to rcu_note_context_switch()	2014-11-03 19:20:34 -08:00
stacktrace.c	stacktrace: introduce snprint_stack_trace for buffer output	2014-12-13 12:42:48 -08:00
stop_machine.c	kernel/stop_machine.c: kernel-doc warning fix	2014-06-04 16:54:15 -07:00
sys.c	x86, mpx: On-demand kernel allocation of bounds tables	2014-11-18 00:58:53 +01:00
sys_ni.c	syscalls: implement execveat() system call	2014-12-13 12:42:51 -08:00
sysctl.c	As the merge window is still open, and this code was not as complex	2014-12-16 12:53:59 -08:00
sysctl_binary.c	kernel: add panic_on_warn	2014-12-10 17:41:10 -08:00
system_certificates.S	KEYS: correct alignment of system_certificate_list content in assembly file	2013-12-10 18:25:28 +00:00
system_keyring.c	KEYS: validate certificate trust only with builtin keys	2014-07-17 09:35:17 -04:00
task_work.c	…
taskstats.c	kill f_dentry uses	2014-11-19 13:01:25 -05:00
test_kprobes.c	kernel/test_kprobes.c: use current logging functions	2014-08-08 15:57:18 -07:00
torture.c	torture: Address race in module cleanup	2014-09-16 13:41:06 -07:00
tracepoint.c	tracing: syscall_regfunc() should not skip kernel threads	2014-06-21 00:15:26 -04:00
tsacct.c	sched: Make task->start_time nanoseconds based	2014-07-23 10:18:05 -07:00
uid16.c	groups: Consolidate the setgroups permission checks	2014-12-05 17:19:27 -06:00
up.c	smp: Rename __smp_call_function_single() to smp_call_function_single_async()	2014-02-24 14:47:15 -08:00
user-return-notifier.c	scheduler: Replace __get_cpu_var with this_cpu_ptr	2014-08-26 13:45:45 -04:00
user.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2014-12-17 12:31:40 -08:00
user_namespace.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2014-12-17 12:31:40 -08:00
utsname.c	copy address of proc_ns_ops into ns_common	2014-12-04 14:34:47 -05:00
utsname_sysctl.c	sysctl: convert use of typedef ctl_table to struct ctl_table	2014-06-06 16:08:16 -07:00
watchdog.c	Merge branch 'for-3.18-consistent-ops' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu	2014-10-15 07:48:18 +02:00
workqueue.c	workqueue: allow rescuer thread to do more work.	2014-12-08 12:39:16 -05:00
workqueue_internal.h	workqueue: rename manager_mutex to attach_mutex	2014-05-20 10:59:32 -04:00