Guilherme G. Piccoli 106a648780 clocksource: Fix the CPUs' choice in the watchdog per CPU verification ... [ Upstream commit 08d7becc1a ] Right now, if the clocksource watchdog detects a clocksource skew, it might perform a per CPU check, for example in the TSC case on x86. In other words: supposing TSC is detected as unstable by the clocksource watchdog running at CPU1, as part of marking TSC unstable the kernel will also run a check of TSC readings on some CPUs to be sure it is synced between them all. But that check happens only on some CPUs, not all of them; this choice is based on the parameter "verify_n_cpus" and in some random cpumask calculation. So, the watchdog runs such per CPU checks on up to "verify_n_cpus" random CPUs among all online CPUs, with the risk of repeating CPUs (that aren't double checked) in the cpumask random calculation. But if "verify_n_cpus" > num_online_cpus(), it should skip the random calculation and just go ahead and check the clocksource sync between all online CPUs, without the risk of skipping some CPUs due to duplicity in the random cpumask calculation. Tests in a 4 CPU laptop with TSC skew detected led to some cases of the per CPU verification skipping some CPU even with verify_n_cpus=8, due to the duplicity on random cpumask generation. Skipping the randomization when the number of online CPUs is smaller than verify_n_cpus, solves that. Suggested-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com> Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Paul E. McKenney <paulmck@kernel.org> Link: https://lore.kernel.org/all/20250323173857.372390-1-gpiccoli@igalia.com Signed-off-by: Sasha Levin <sashal@kernel.org>		2025-06-27 11:05:27 +01:00
..
bpf	bpf: Avoid __bpf_prog_ret0_warn when jit fails	2025-06-27 11:05:14 +01:00
cgroup	cgroup: Fix compilation issue due to cgroup_mutex not being exported	2025-06-04 14:37:54 +02:00
configs
debug	kdb: Do not assume write() callback available	2025-03-13 12:50:45 +01:00
dma	dma/contiguous: avoid warning about unused size_bytes	2025-05-02 07:44:29 +02:00
entry	entry: Respect changes to system call number by trace_sys_enter()	2024-04-10 16:18:46 +02:00
events	perf: Ensure bpf_perf_link path is properly serialized	2025-06-27 11:05:20 +01:00
futex	futex: Don't include process MM in futex key on no-MMU	2023-11-20 11:08:13 +01:00
gcov	gcov: add support for GCC 14	2024-07-05 09:14:34 +02:00
irq	genirq: Make handle_enforce_irqctx() unconditionally available	2025-03-13 12:49:52 +01:00
kcsan	kcsan: Turn report_filterlist_lock into a raw_spinlock	2024-12-14 19:51:35 +01:00
livepatch	livepatch: Fix missing newline character in klp_resolve_symbols()	2023-11-20 11:08:25 +01:00
locking	locking/lockdep: Decrease nr_unused_locks if lock unused in zap_class()	2025-05-02 07:44:03 +02:00
power	PM: wakeup: Delete space in the end of string shown by pm_show_wakelocks()	2025-06-27 11:05:10 +01:00
printk	printk: Fix signed integer overflow when defining LOG_BUF_LEN_MAX	2025-03-13 12:50:17 +01:00
rcu	rcu: handle quiescent states for PREEMPT_RCU=n, PREEMPT_COUNT=y	2025-06-04 14:38:03 +02:00
sched	cpufreq/sched: Fix the usage of CPUFREQ_NEED_UPDATE_LIMITS	2025-05-02 07:44:11 +02:00
time	clocksource: Fix the CPUs' choice in the watchdog per CPU verification	2025-06-27 11:05:27 +01:00
trace	ftrace: Fix UAF when lookup kallsym after ftrace disabled	2025-06-27 11:05:26 +01:00
.gitignore
acct.c	acct: block access to kernel internal filesystems	2025-03-13 12:50:54 +01:00
async.c	async: Introduce async_schedule_dev_nocall()	2024-02-23 08:54:25 +01:00
audit_fsnotify.c	fsnotify: make allow_dups a property of the group	2024-04-10 16:19:02 +02:00
audit_tree.c	fsnotify: pass flags argument to fsnotify_alloc_group()	2024-04-10 16:19:02 +02:00
audit_watch.c	fsnotify: pass flags argument to fsnotify_alloc_group()	2024-04-10 16:19:02 +02:00
audit.c	audit: Send netlink ACK before setting connection in auditd_set	2024-02-23 08:54:37 +01:00
audit.h	audit: log AUDIT_TIME_* records only from rules	2022-04-08 14:23:06 +02:00
auditfilter.c	ima: Avoid blocking in RCU read-side critical section	2024-07-18 13:07:34 +02:00
auditsc.c	audit: fix possible soft lockup in __audit_inode_child()	2023-09-19 12:22:39 +02:00
backtracetest.c
bounds.c	bounds: Use the right number of bits for power-of-two CONFIG_NR_CPUS	2024-05-02 16:24:50 +02:00
capability.c
cfi.c	cfi: Fix __cfi_slowpath_diag RCU usage with cpuidle	2022-06-22 14:22:04 +02:00
compat.c	sched_getaffinity: don't assume 'cpumask_size()' is fully initialized	2023-04-05 11:24:53 +02:00
configs.c
context_tracking.c
cpu_pm.c
cpu.c	hrtimers: Handle CPU state correctly on hotplug	2025-01-23 17:16:02 +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	cred: switch to using atomic_long_t	2023-12-20 15:17:37 +01:00
delayacct.c
dma.c
exec_domain.c
exit.c	mm: optimize the redundant loop of mm_update_owner_next()	2024-07-18 13:07:32 +02:00
extable.c
fail_function.c	kernel/fail_function: fix memory leak with using debugfs_lookup()	2023-03-11 13:57:38 +01:00
fork.c	fork: use pidfd_prepare()	2025-06-04 14:38:07 +02:00
freezer.c
gen_kheaders.sh	kheaders: Ignore silly-rename files	2025-01-23 17:16:00 +01:00
groups.c
hung_task.c	hung_task: move hung_task sysctl interface to hung_task.c	2025-03-13 12:49:50 +01:00
iomem.c
irq_work.c
jump_label.c
kallsyms.c	kallsyms: Make kallsyms_on_each_symbol generally available	2023-12-13 18:36:45 +01:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt
kcov.c	kcov: mark in_softirq_really() as __always_inline	2025-01-09 13:28:50 +01:00
kexec_core.c	kexec: fix a memory leak in crash_shrink_memory()	2023-07-23 13:46:52 +02:00
kexec_elf.c	kexec: initialize ELF lowest address to ULONG_MAX	2025-04-10 14:32:01 +02:00
kexec_file.c	kexec: support purgatories with .text.hot sections	2023-06-21 15:59:14 +02:00
kexec_internal.h	panic, kexec: make __crash_kexec() NMI safe	2023-04-20 12:13:57 +02:00
kexec.c	kernel: kexec: copy user-array safely	2023-11-28 16:56:16 +00:00
kheaders.c	kheaders: Use array declaration instead of char	2023-05-11 23:00:17 +09:00
kmod.c
kprobes.c	kprobes: Fix to check symbol prefixes correctly	2024-08-19 05:45:42 +02:00
ksysfs.c	kexec: turn all kexec_mutex acquisitions into trylocks	2023-04-20 12:13:57 +02:00
kthread.c	kthread: unpark only parked kthread	2024-10-17 15:12:00 +02:00
latencytop.c
Makefile	futex: Move to kernel/futex/	2022-12-31 13:14:04 +01:00
module_signature.c
module_signing.c
module-internal.h
module.c	NFSD: Remove svc_serv_ops::svo_module	2024-04-10 16:19:01 +02:00
notifier.c
nsproxy.c
padata.c	padata: do not leak refcount in reorder_work	2025-06-04 14:38:05 +02:00
panic.c	panic: Flush kernel log buffer at the end	2024-04-13 13:01:43 +02:00
params.c	module: ensure that kobject_put() is safe for module type kobjects	2025-05-18 08:20:37 +02:00
pid_namespace.c	zap_pid_ns_processes: clear TIF_NOTIFY_SIGNAL along with TIF_SIGPENDING	2024-07-05 09:14:24 +02:00
pid.c
profile.c	profiling: remove profile=sleep support	2024-08-19 05:45:39 +02:00
ptrace.c	ptrace: Reimplement PTRACE_KILL by always sending SIGKILL	2022-06-09 10:22:29 +02:00
range.c
reboot.c	kernel/reboot: emergency_restart: Set correct system_state	2023-11-28 16:56:31 +00:00
regset.c
relay.c	relayfs: fix out-of-bounds access in relay_file_read	2023-05-11 23:00:18 +09:00
resource_kunit.c
resource.c	resource: fix region_intersects() vs add_memory_driver_managed()	2024-10-17 15:11:59 +02:00
rseq.c	rseq: Remove broken uapi field layout on 32-bit little endian	2022-04-08 14:23:10 +02:00
scftorture.c	scftorture: Forgive memory-allocation failure if KASAN	2023-09-23 11:09:55 +02:00
scs.c
seccomp.c	seccomp: Invalidate seccomp mode to catch death failures	2022-02-16 12:56:38 +01:00
signal.c	signal: Replace BUG_ON()s	2024-10-17 15:11:27 +02:00
smp.c	smp: Add missing destroy_work_on_stack() call in smp_call_on_cpu()	2024-09-12 11:07:49 +02:00
smpboot.c
smpboot.h
softirq.c	lockdep: Fix wait context check on softirq for PREEMPT_RT	2025-06-04 14:37:55 +02:00
stackleak.c	gcc-plugins/stackleak: Use noinstr in favor of notrace	2022-02-23 12:03:07 +01:00
stacktrace.c	stacktrace: move filter_irq_stacks() to kernel/stacktrace.c	2022-04-13 20:59:28 +02:00
static_call_inline.c	x86/static-call: provide a way to do very early static-call updates	2024-12-19 18:07:22 +01:00
static_call.c	static_call: Don't make __static_call_return0 static	2022-04-13 20:59:28 +02:00
stop_machine.c
sys_ni.c	syscalls: fix compat_sys_io_pgetevents_time64 usage	2024-07-05 09:14:50 +02:00
sys.c	getrusage: use sig->stats_lock rather than lock_task_sighand()	2024-03-15 10:48:22 -04:00
sysctl-test.c
sysctl.c	fs: move fs stat sysctls to file_table.c	2025-03-13 12:49:50 +01:00
task_work.c	task_work: Introduce task_work_cancel() again	2024-08-19 05:45:13 +02:00
taskstats.c
test_kprobes.c
torture.c	torture: Fix hang during kthread shutdown phase	2023-08-30 16:18:19 +02:00
tracepoint.c
tsacct.c	taskstats: Cleanup the use of task->exit_code	2022-01-27 11:05:35 +01:00
ucount.c	ucounts: fix counter leak in inc_rlimit_get_ucounts()	2024-11-14 13:13:42 +01:00
uid16.c
uid16.h
umh.c
up.c
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
usermode_driver.c
utsname_sysctl.c
utsname.c
watch_queue.c	watch_queue: fix pipe accounting mismatch	2025-04-10 14:31:57 +02:00
watchdog_hld.c	watchdog/perf: properly initialize the turbo mode timestamp and rearm counter	2024-08-19 05:45:20 +02:00
watchdog.c	watchdog: move softlockup_panic back to early_param	2023-11-28 16:56:28 +00:00
workqueue_internal.h
workqueue.c	workqueue: Improve scalability of workqueue watchdog touch	2024-09-12 11:07:52 +02:00