Paul E. McKenney e3663b1024 rcu: Handle gpnum/completed wrap while dyntick idle ... Subtle race conditions can result if a CPU stays in dyntick-idle mode long enough for the ->gpnum and ->completed fields to wrap. For example, consider the following sequence of events: o CPU 1 encounters a quiescent state while waiting for grace period 5 to complete, but then enters dyntick-idle mode. o While CPU 1 is in dyntick-idle mode, the grace-period counters wrap around so that the grace period number is now 4. o Just as CPU 1 exits dyntick-idle mode, grace period 4 completes and grace period 5 begins. o The quiescent state that CPU 1 passed through during the old grace period 5 looks like it applies to the new grace period 5. Therefore, the new grace period 5 completes without CPU 1 having passed through a quiescent state. This could clearly be a fatal surprise to any long-running RCU read-side critical section that happened to be running on CPU 1 at the time. At one time, this was not a problem, given that it takes significant time for the grace-period counters to overflow even on 32-bit systems. However, with the advent of NO_HZ_FULL and SMP embedded systems, arbitrarily long idle periods are now becoming quite feasible. It is therefore time to close this race. This commit therefore avoids this race condition by having the quiescent-state forcing code detect when a CPU is falling too far behind, and setting a new rcu_data field ->gpwrap when this happens. Whenever this new ->gpwrap field is set, the CPU's ->gpnum and ->completed fields are known to be untrustworthy, and can be ignored, along with any associated quiescent states. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>		2015-01-06 11:05:28 -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: Handle gpnum/completed wrap while dyntick idle	2015-01-06 11:05:28 -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
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
bounds.c	page-cgroup: get rid of NR_PCG_FLAGS	2014-08-08 15:57:18 -07:00
capability.c
cgroup.c	cgroup: implement cgroup_get_e_css()	2014-11-18 02:49:52 -05:00
cgroup_freezer.c
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
dma.c
elfcore.c
exec_domain.c
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
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
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
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
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
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
Makefile	kernel: res_counter: remove the unused API	2014-12-10 17:41:04 -08:00
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
nsproxy.c	bury struct proc_ns in fs/proc	2014-12-04 14:34:54 -05:00
padata.c
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
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
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
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
system_keyring.c
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
tsacct.c
uid16.c	groups: Consolidate the setgroups permission checks	2014-12-05 17:19:27 -06:00
up.c
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
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