Phil Auld 00b32ad42d sched/fair: Limit sched_cfs_period_timer() loop to avoid hard lockup ... [ Upstream commit 2e8e19226398db8265a8e675fcc0118b9e80c9e8 ] With extremely short cfs_period_us setting on a parent task group with a large number of children the for loop in sched_cfs_period_timer() can run until the watchdog fires. There is no guarantee that the call to hrtimer_forward_now() will ever return 0. The large number of children can make do_sched_cfs_period_timer() take longer than the period. NMI watchdog: Watchdog detected hard LOCKUP on cpu 24 RIP: 0010:tg_nop+0x0/0x10 <IRQ> walk_tg_tree_from+0x29/0xb0 unthrottle_cfs_rq+0xe0/0x1a0 distribute_cfs_runtime+0xd3/0xf0 sched_cfs_period_timer+0xcb/0x160 ? sched_cfs_slack_timer+0xd0/0xd0 __hrtimer_run_queues+0xfb/0x270 hrtimer_interrupt+0x122/0x270 smp_apic_timer_interrupt+0x6a/0x140 apic_timer_interrupt+0xf/0x20 </IRQ> To prevent this we add protection to the loop that detects when the loop has run too many times and scales the period and quota up, proportionally, so that the timer can complete before then next period expires. This preserves the relative runtime quota while preventing the hard lockup. A warning is issued reporting this state and the new values. Signed-off-by: Phil Auld <pauld@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: <stable@vger.kernel.org> Cc: Anton Blanchard <anton@ozlabs.org> Cc: Ben Segall <bsegall@google.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20190319130005.25492-1-pauld@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2019-07-27 22:10:10 +02:00
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auto_group.c	sched/autogroup: Fix possible Spectre-v1 indexing for sched_prio_to_weight[]	2019-07-27 21:52:06 +02:00
auto_group.h
clock.c
core.c	sched/core: Fix TASK_DEAD race in finish_task_switch()	2019-07-27 22:09:34 +02:00
cpuacct.c
cpuacct.h
cpudeadline.c
cpudeadline.h
cpupri.c
cpupri.h
cputime.c	sched: Change thread_group_cputime() to use for_each_thread()	2019-07-27 22:09:16 +02:00
deadline.c
debug.c	sched: print_rq(): Don't use tasklist_lock	2019-07-27 22:09:20 +02:00
fair.c	sched/fair: Limit sched_cfs_period_timer() loop to avoid hard lockup	2019-07-27 22:10:10 +02:00
features.h	Import latest Samsung release	2017-04-18 03:43:52 +02:00
idle_task.c
Makefile
rt.c
sched.h	sched/core: Fix TASK_DEAD race in finish_task_switch()	2019-07-27 22:09:34 +02:00
sched_avg.c	sched: Fix integer overflow in sched_update_nr_prod()	2016-09-29 02:12:18 -07:00
stats.c
stats.h
stop_task.c
wait.c