Valentin Schneider 1e0e63ad62 sched/rt: Plug rt_mutex_setprio() vs push_rt_task() race ... [ Upstream commit 49bef33e4b ] John reported that push_rt_task() can end up invoking find_lowest_rq(rq->curr) when curr is not an RT task (in this case a CFS one), which causes mayhem down convert_prio(). This can happen when current gets demoted to e.g. CFS when releasing an rt_mutex, and the local CPU gets hit with an rto_push_work irqwork before getting the chance to reschedule. Exactly who triggers this work isn't entirely clear to me - switched_from_rt() only invokes rt_queue_pull_task() if there are no RT tasks on the local RQ, which means the local CPU can't be in the rto_mask. My current suspected sequence is something along the lines of the below, with the demoted task being current. mark_wakeup_next_waiter() rt_mutex_adjust_prio() rt_mutex_setprio() // deboost originally-CFS task check_class_changed() switched_from_rt() // Only rt_queue_pull_task() if !rq->rt.rt_nr_running switched_to_fair() // Sets need_resched __balance_callbacks() // if pull_rt_task(), tell_cpu_to_push() can't select local CPU per the above raw_spin_rq_unlock(rq) // need_resched is set, so task_woken_rt() can't // invoke push_rt_tasks(). Best I can come up with is // local CPU has rt_nr_migratory >= 2 after the demotion, so stays // in the rto_mask, and then: <some other CPU running rto_push_irq_work_func() queues rto_push_work on this CPU> push_rt_task() // breakage follows here as rq->curr is CFS Move an existing check to check rq->curr vs the next pushable task's priority before getting anywhere near find_lowest_rq(). While at it, add an explicit sched_class of rq->curr check prior to invoking find_lowest_rq(rq->curr). Align the DL logic to also reschedule regardless of next_task's migratability. Fixes: a7c81556ec ("sched: Fix migrate_disable() vs rt/dl balancing") Reported-by: John Keeping <john@metanate.com> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: John Keeping <john@metanate.com> Link: https://lore.kernel.org/r/20220127154059.974729-1-valentin.schneider@arm.com Signed-off-by: Sasha Levin <sashal@kernel.org>		2022-04-08 14:23:11 +02:00
..
bpf	bpf: Fix possible race in inc_misses_counter	2022-03-08 19:12:40 +01:00
cgroup	cgroup-v1: Correct privileges check in release_agent writes	2022-03-02 11:47:47 +01:00
configs	drivers/char: remove /dev/kmem for good	2021-05-07 00:26:34 -07:00
debug	kdb: Adopt scheduler's task classification	2021-11-18 19:17:06 +01:00
dma	Revert "swiotlb: rework "fix info leak with DMA_FROM_DEVICE""	2022-04-08 14:22:45 +02:00
entry	signal: Replace force_fatal_sig with force_exit_sig when in doubt	2021-11-25 09:49:07 +01:00
events	perf/core: Fix address filter parser for multiple filters	2022-04-08 14:23:10 +02:00
gcov	Kconfig: Introduce ARCH_WANTS_NO_INSTR and CC_HAS_NO_PROFILE_FN_ATTR	2021-06-22 11:07:18 -07:00
irq	PCI/MSI: Move non-mask check back into low level accessors	2021-11-18 19:17:14 +01:00
kcsan	LKMM updates:	2021-09-02 13:00:15 -07:00
livepatch	livepatch: Replace deprecated CPU-hotplug functions.	2021-08-19 12:00:24 +02:00
locking	locking/lockdep: Avoid potential access of invalid memory in lock_class	2022-04-08 14:22:48 +02:00
power	PM: suspend: fix return value of __setup handler	2022-04-08 14:23:07 +02:00
printk	printk: restore flushing of NMI buffers on remote CPUs after NMI backtraces	2021-11-25 09:48:45 +01:00
rcu	rcu: Don't deboost before reporting expedited quiescent state	2022-03-28 09:58:45 +02:00
sched	sched/rt: Plug rt_mutex_setprio() vs push_rt_task() race	2022-04-08 14:23:11 +02:00
time	clocksource: Avoid accidental unstable marking of clocksources	2022-01-27 11:04:08 +01:00
trace	tracing: Have trace event string test handle zero length strings	2022-04-08 14:22:57 +02:00
.gitignore	.gitignore: prefix local generated files with a slash	2021-05-02 00:43:35 +09:00
acct.c	kernel/acct.c: use dedicated helper to access rlimit values	2021-09-08 11:50:26 -07:00
async.c	Revert "module, async: async_synchronize_full() on module init iff async is used"	2022-02-23 12:03:07 +01:00
audit_fsnotify.c
audit_tree.c	audit: move put_tree() to avoid trim_trees refcount underflow and UAF	2021-08-24 18:52:36 -04:00
audit_watch.c
audit.c	audit: improve audit queue handling when "audit=1" on cmdline	2022-02-08 18:34:03 +01:00
audit.h	audit: log AUDIT_TIME_* records only from rules	2022-04-08 14:23:06 +02:00
auditfilter.c	lsm: separate security_task_getsecid() into subjective and objective variants	2021-03-22 15:23:32 -04:00
auditsc.c	audit: log AUDIT_TIME_* records only from rules	2022-04-08 14:23:06 +02:00
backtracetest.c
bounds.c
capability.c
cfi.c	cfi: Use rcu_read_{un}lock_sched_notrace	2021-08-11 13:11:12 -07:00
compat.c	arch: remove compat_alloc_user_space	2021-09-08 15:32:35 -07:00
configs.c
context_tracking.c
cpu_pm.c	PM: cpu: Make notifier chain use a raw_spinlock_t	2021-08-16 18:55:32 +02:00
cpu.c	sched/scs: Reset task stack state in bringup_cpu()	2021-12-01 09:04:54 +01:00
crash_core.c	kernel/crash_core: suppress unknown crashkernel parameter warning	2021-12-29 12:28:49 +01:00
crash_dump.c
cred.c	ucounts: Base set_cred_ucounts changes on the real user	2022-02-23 12:03:20 +01:00
delayacct.c	delayacct: Add sysctl to enable at runtime	2021-05-12 11:43:25 +02:00
dma.c
exec_domain.c
exit.c	io_uring: remove files pointer in cancellation functions	2021-08-23 13:10:37 -06:00
extable.c
fail_function.c
fork.c	sched: Fix yet more sched_fork() races	2022-03-08 19:12:49 +01:00
freezer.c	sched: Add get_current_state()	2021-06-18 11:43:08 +02:00
futex.c	futex: Remove unused variable 'vpid' in futex_proxy_trylock_atomic()	2021-09-03 23:00:22 +02:00
gen_kheaders.sh	kbuild: clean up ${quiet} checks in shell scripts	2021-05-27 04:01:50 +09:00
groups.c
hung_task.c	Merge branch 'akpm' (patches from Andrew)	2021-07-02 12:08:10 -07:00
iomem.c
irq_work.c	irq_work: Make irq_work_queue() NMI-safe again	2021-06-10 10:00:08 +02:00
jump_label.c	jump_label: Fix jump_label_text_reserved() vs __init	2021-07-05 10:46:20 +02:00
kallsyms.c	module: add printk formats to add module build ID to stacktraces	2021-07-08 11:48:22 -07:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks	locking/rwlock: Provide RT variant	2021-08-17 17:50:51 +02:00
Kconfig.preempt	sched/core: Disable CONFIG_SCHED_CORE by default	2021-06-28 22:43:05 +02:00
kcov.c
kexec_core.c	Merge branch 'rework/printk_safe-removal' into for-linus	2021-08-30 16:36:10 +02:00
kexec_elf.c
kexec_file.c	kernel: kexec_file: fix error return code of kexec_calculate_store_digests()	2021-05-07 00:26:32 -07:00
kexec_internal.h
kexec.c	kexec: avoid compat_alloc_user_space	2021-09-08 15:32:34 -07:00
kheaders.c
kmod.c	modules: add CONFIG_MODPROBE_PATH	2021-05-07 00:26:33 -07:00
kprobes.c	kprobes: Limit max data_size of the kretprobe instances	2021-12-08 09:04:41 +01:00
ksysfs.c
kthread.c	Merge branch 'akpm' (patches from Andrew)	2021-06-29 17:29:11 -07:00
latencytop.c
Makefile	kbuild: update config_data.gz only when the content of .config is changed	2021-05-02 00:43:35 +09:00
module_signature.c
module_signing.c
module-internal.h
module.c	Revert "module, async: async_synchronize_full() on module init iff async is used"	2022-02-23 12:03:07 +01:00
notifier.c	notifier: Remove atomic_notifier_call_chain_robust()	2021-08-16 18:55:32 +02:00
nsproxy.c	memcg: enable accounting for new namesapces and struct nsproxy	2021-09-03 09:58:12 -07:00
padata.c	padata: Remove repeated verbose license text	2021-08-27 16:30:18 +08:00
panic.c	Merge branch 'rework/printk_safe-removal' into for-linus	2021-08-30 16:36:10 +02:00
params.c	params: lift param_set_uint_minmax to common code	2021-08-16 14:42:22 +02:00
pid_namespace.c	memcg: enable accounting for new namesapces and struct nsproxy	2021-09-03 09:58:12 -07:00
pid.c	kernel/pid.c: implement additional checks upon pidfd_create() parameters	2021-08-10 12:53:07 +02:00
profile.c	profiling: fix shift-out-of-bounds bugs	2021-09-08 11:50:26 -07:00
ptrace.c	ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE	2022-04-08 14:22:50 +02:00
range.c
reboot.c	reboot: Add hardware protection power-off	2021-06-21 13:08:36 +01:00
regset.c
relay.c
resource_kunit.c
resource.c	kernel/resource: fix return code check in __request_free_mem_region	2021-05-14 19:41:32 -07:00
rseq.c	rseq: Remove broken uapi field layout on 32-bit little endian	2022-04-08 14:23:10 +02:00
scftorture.c	scftorture: Avoid NULL pointer exception on early exit	2021-07-27 11:39:30 -07:00
scs.c	scs: Release kasan vmalloc poison in scs_free process	2021-11-18 19:16:29 +01:00
seccomp.c	seccomp: Invalidate seccomp mode to catch death failures	2022-02-16 12:56:38 +01:00
signal.c	signal: In get_signal test for signal_group_exit every time through the loop	2022-03-08 19:12:34 +01:00
smp.c	smp: Fix all kernel-doc warnings	2021-08-11 14:47:16 +02:00
smpboot.c	smpboot: Replace deprecated CPU-hotplug functions.	2021-08-10 14:57:42 +02:00
smpboot.h
softirq.c	genirq: Change force_irqthreads to a static key	2021-08-10 22:50:07 +02:00
stackleak.c	gcc-plugins/stackleak: Use noinstr in favor of notrace	2022-02-23 12:03:07 +01:00
stacktrace.c
static_call.c	static_call: Fix static_call_text_reserved() vs __init	2021-07-05 10:46:33 +02:00
stop_machine.c	stop_machine: Add caller debug info to queue_stop_cpus_work	2021-03-23 16:01:58 +01:00
sys_ni.c	compat: remove some compat entry points	2021-09-08 15:32:35 -07:00
sys.c	ucounts: Move RLIMIT_NPROC handling after set_user	2022-02-23 12:03:20 +01:00
sysctl-test.c	kernel/sysctl-test: Remove some casts which are no-longer required	2021-06-23 16:41:24 -06:00
sysctl.c	x86/speculation: Include unprivileged eBPF status in Spectre v2 mitigation reporting	2022-03-11 12:22:31 +01:00
task_work.c	kasan: record task_work_add() call stack	2021-04-30 11:20:42 -07:00
taskstats.c
test_kprobes.c
torture.c	torture: Replace deprecated CPU-hotplug functions.	2021-08-10 10:48:07 -07:00
tracepoint.c	tracepoint: Fix kerneldoc comments	2021-08-16 11:39:51 -04:00
tsacct.c	taskstats: Cleanup the use of task->exit_code	2022-01-27 11:05:35 +01:00
ucount.c	ucounts: Handle wrapping in is_ucounts_overlimit	2022-02-23 12:03:20 +01:00
uid16.c
uid16.h
umh.c	kernel/umh.c: fix some spelling mistakes	2021-05-07 00:26:34 -07:00
up.c	A set of locking related fixes and updates:	2021-05-09 13:07:03 -07:00
user_namespace.c	ucounts: Fix systemd LimitNPROC with private users regression	2022-03-08 19:12:42 +01:00
user-return-notifier.c
user.c	fs/epoll: use a per-cpu counter for user's watches count	2021-09-08 11:50:27 -07:00
usermode_driver.c	Merge branch 'work.namei' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2021-07-03 11:41:14 -07:00
utsname_sysctl.c
utsname.c
watch_queue.c	watch_queue: Actually free the watch	2022-04-08 14:23:10 +02:00
watchdog_hld.c
watchdog.c	kernel: watchdog: modify the explanation related to watchdog thread	2021-06-29 10:53:46 -07:00
workqueue_internal.h	workqueue: Assign a color to barrier work items	2021-08-17 07:49:10 -10:00
workqueue.c	workqueue: Fix unbind_workers() VS wq_worker_running() race	2022-01-16 09:12:41 +01:00