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Ben Segall 54d27365ca sched/fair: Prevent throttling in early pick_next_task_fair() 
The optimized task selection logic optimistically selects a new task
to run without first doing a full put_prev_task(). This is so that we
can avoid a put/set on the common ancestors of the old and new task.

Similarly, we should only call check_cfs_rq_runtime() to throttle
eligible groups if they're part of the common ancestry, otherwise it
is possible to end up with no eligible task in the simple task
selection.

Imagine:
		/root
	/prev		/next
	/A		/B

If our optimistic selection ends up throttling /next, we goto simple
and our put_prev_task() ends up throttling /prev, after which we're
going to bug out in set_next_entity() because there aren't any tasks
left.

Avoid this scenario by only throttling common ancestors.

Reported-by: Mohammed Naser <mnaser@vexxhost.com>
Reported-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Ben Segall <bsegall@google.com>
[ munged Changelog ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <klamm@yandex-team.ru>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: pjt@google.com
Fixes: 678d5718d8 ("sched/fair: Optimize cgroup pick_next_task_fair()")
Link: http://lkml.kernel.org/r/xm26wq1oswoq.fsf@sword-of-the-dawn.mtv.corp.google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
 		2015-06-07 15:57:44 +02:00
..
bpf bpf: fix 64-bit divide 2015-04-27 23:11:49 -04:00
configs
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debug debug: prevent entering debug mode on panic/exception. 2015-02-19 12:39:03 -06:00
events perf: Annotate inherited event ctx->mutex recursion 2015-05-08 11:59:40 +02:00
gcov gcov: fix softlockups 2015-04-17 09:04:08 -04:00
irq genirq: Set IRQCHIP_SKIP_SET_WAKE flag for dummy_irq_chip 2015-04-24 20:57:06 +02:00
livepatch Merge branch 'for-4.1/core-noarch' into for-linus 2015-04-13 23:57:20 +02:00
locking sched: Handle priority boosted tasks proper in setscheduler() 2015-05-08 11:53:55 +02:00
power Merge back earlier suspend/hibernate material for v4.1. 2015-04-10 12:01:59 +02:00
printk TTY/Serial patches for 4.1-rc1 2015-04-21 09:33:10 -07:00
rcu rcu: Control grace-period delays directly from value 2015-04-14 19:33:59 -07:00
sched sched/fair: Prevent throttling in early pick_next_task_fair() 2015-06-07 15:57:44 +02:00
time Merge branch 'linus' into sched/core, to resolve conflict 2015-06-02 08:05:42 +02:00
trace tracing: Make ftrace_print_array_seq compute buf_len 2015-05-06 23:03:23 -04:00
.gitignore
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Kconfig.freezer
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Kconfig.hz
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Kconfig.locks locking/mcs: Better differentiate between MCS variants 2015-01-14 15:07:32 +01:00
Kconfig.preempt
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Makefile modsign: change default key details 2015-04-30 09:35:41 -07:00
acct.c acct: check FMODE_CAN_WRITE 2015-04-11 22:27:55 -04:00
async.c
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audit.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-26 17:22:07 -07:00
audit.h Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit 2015-04-22 14:49:23 -07:00
audit_tree.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-26 17:22:07 -07:00
audit_watch.c VFS: audit: d_backing_inode() annotations 2015-04-15 15:06:55 -04:00
auditfilter.c Merge branch 'upstream' of git://git.infradead.org/users/pcmoore/audit 2015-02-11 20:07:47 -08:00
auditsc.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2015-04-26 17:22:07 -07:00
backtracetest.c
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bounds.c
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capability.c kernel: conditionally support non-root users, groups and capabilities 2015-04-15 16:35:22 -07:00
cgroup.c cgroup: remove use of seq_printf return value 2015-04-15 16:35:25 -07:00
cgroup_freezer.c
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compat.c all arches, signal: move restart_block to struct task_struct 2015-02-12 18:54:12 -08:00
configs.c
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context_tracking.c context_tracking: Export context_tracking_user_enter/exit 2015-03-09 15:43:00 +01:00
cpu.c Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-04-14 13:36:04 -07:00
cpu_pm.c
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cpuset.c kernel, cpuset: remove exception for __GFP_THISNODE 2015-04-14 16:49:03 -07:00
crash_dump.c
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cred.c kernel: conditionally support non-root users, groups and capabilities 2015-04-15 16:35:22 -07:00
delayacct.c
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dma.c
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elfcore.c
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exec_domain.c Remove rest of exec domains. 2015-04-12 21:03:31 +02:00
exit.c Remove execution domain support 2015-04-12 20:58:24 +02:00
extable.c ftrace/x86/extable: Add is_ftrace_trampoline() function 2014-11-19 15:25:26 -05:00
fork.c sched/preempt, mm/fault: Count pagefault_disable() levels in pagefault_disabled 2015-05-19 08:39:13 +02:00
freezer.c
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futex.c futex: Implement lockless wakeups 2015-05-08 12:21:40 +02:00
futex_compat.c
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groups.c kernel: conditionally support non-root users, groups and capabilities 2015-04-15 16:35:22 -07:00
hung_task.c kernel/hung_task.c: change hung_task.c to use for_each_process_thread() 2015-04-15 16:35:22 -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
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kallsyms.c
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kcmp.c
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kexec.c kexec: allocate the kexec control page with KEXEC_CONTROL_MEMORY_GFP 2015-04-23 16:52:01 +02:00
kmod.c usermodehelper: kill the kmod_thread_locker logic 2014-12-10 17:41:17 -08:00
kprobes.c kprobes: makes kprobes/enabled works correctly for optimized kprobes. 2015-02-13 21:21:42 -08:00
ksysfs.c
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kthread.c
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latencytop.c
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module-internal.h
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module.c module: Call module notifier on failure after complete_formation() 2015-05-09 03:29:24 +09:30
module_signing.c
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notifier.c rcu: Make SRCU optional by using CONFIG_SRCU 2015-01-06 11:04:29 -08:00
nsproxy.c bury struct proc_ns in fs/proc 2014-12-04 14:34:54 -05:00
padata.c padata: use %*pb[l] to print bitmaps including cpumasks and nodemasks 2015-02-13 21:21:38 -08:00
panic.c livepatch: kernel: add TAINT_LIVEPATCH 2014-12-22 15:40:48 +01:00
params.c params: handle quotes properly for values not of form foo="bar". 2015-04-15 13:31:23 +09:30
pid.c fork: report pid reservation failure properly 2015-04-17 09:04:06 -04:00
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 profile: use %*pb[l] to print bitmaps including cpumasks and nodemasks 2015-02-13 21:21:38 -08:00
ptrace.c ptrace: ptrace_detach() can no longer race with SIGKILL 2015-04-17 09:04:06 -04:00
range.c kernel: avoid overflow in cmp_range 2015-01-17 10:02:23 +13:00
reboot.c kernel/reboot.c: add orderly_reboot for graceful reboot 2015-04-15 16:35:23 -07:00
relay.c VFS: kernel/: d_inode() annotations 2015-04-15 15:06:55 -04:00
resource.c kernel/resource.c: remove deprecated __check_region() and friends 2015-04-15 16:35:22 -07:00
seccomp.c seccomp: cap SECCOMP_RET_ERRNO data to MAX_ERRNO 2015-02-17 14:34:55 -08:00
signal.c signals, sched: Change all uses of JOBCTL_* from 'int' to 'long' 2015-05-08 12:04:36 +02:00
smp.c smp: Fix error case handling in smp_call_function_*() 2015-04-19 13:19:23 -07:00
smpboot.c smpboot: Add common code for notification from dying CPU 2015-03-11 13:20:25 -07:00
smpboot.h
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softirq.c Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-02-09 15:24:03 -08:00
stacktrace.c stacktrace: introduce snprint_stack_trace for buffer output 2014-12-13 12:42:48 -08:00
stop_machine.c
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sys.c prctl: avoid using mmap_sem for exe_file serialization 2015-04-17 09:04:07 -04:00
sys_ni.c kernel: conditionally support non-root users, groups and capabilities 2015-04-15 16:35:22 -07:00
sysctl.c kernel/sysctl.c: detect overflows when converting to int 2015-04-17 09:04:08 -04:00
sysctl_binary.c kernel: add panic_on_warn 2014-12-10 17:41:10 -08:00
system_certificates.S
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system_keyring.c
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task_work.c
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taskstats.c netlink: make nlmsg_end() and genlmsg_end() void 2015-01-18 01:03:45 -05:00
test_kprobes.c
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torture.c
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tracepoint.c
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tsacct.c
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uid16.c groups: Consolidate the setgroups permission checks 2014-12-05 17:19:27 -06:00
up.c
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user-return-notifier.c
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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
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watchdog.c watchdog: fix double lock in watchdog_nmi_enable_all 2015-05-19 10:57:03 -07:00
workqueue.c workqueue: Reorder sysfs code 2015-04-06 11:16:04 -04:00
workqueue_internal.h
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