Petr Mladek 0f90b88dbc watchdog: reliable handling of timestamps ... Commit 9bf3bc949f ("watchdog: cleanup handling of false positives") tried to handle a virtual host stopped by the host a more straightforward and cleaner way. But it introduced a risk of false softlockup reports. The virtual host might be stopped at any time, for example between kvm_check_and_clear_guest_paused() and is_softlockup(). As a result, is_softlockup() might read the updated jiffies and detects a softlockup. A solution might be to put back kvm_check_and_clear_guest_paused() after is_softlockup() and detect it. But it would put back the cycle that complicates the logic. In fact, the handling of all the timestamps is not reliable. The code does not guarantee when and how many times the timestamps are read. For example, "period_ts" might be touched anytime also from NMI and re-read in is_softlockup(). It works just by chance. Fix all the problems by making the code even more explicit. 1. Make sure that "now" and "period_ts" timestamps are read only once. They might be changed at anytime by NMI or when the virtual guest is stopped by the host. Note that "now" timestamp does this implicitly because "jiffies" is marked volatile. 2. "now" time must be read first. The state of "period_ts" will decide whether it will be used or the period will get restarted. 3. kvm_check_and_clear_guest_paused() must be called before reading "period_ts". It touches the variable when the guest was stopped. As a result, "now" timestamp is used only when the watchdog was not touched and the guest not stopped in the meantime. "period_ts" is restarted in all other situations. Link: https://lkml.kernel.org/r/YKT55gw+RZfyoFf7@alley Fixes: 9bf3bc949f ("watchdog: cleanup handling of false positives") Signed-off-by: Petr Mladek <pmladek@suse.com> Reported-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2021-05-22 15:09:07 -10:00
..
bpf	bpf: Fix leakage of uninitialized bpf stack under speculation	2021-05-03 11:56:23 +02:00
cgroup	cgroup: rstat: punt root-level optimization to individual controllers	2021-04-30 11:20:37 -07:00
configs	drivers/char: remove /dev/kmem for good	2021-05-07 00:26:34 -07:00
debug	printk changes for 5.13	2021-04-27 18:09:44 -07:00
dma	Merge branch 'stable/for-linus-5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/konrad/swiotlb	2021-05-04 10:58:49 -07:00
entry	A trivial cleanup of typo fixes.	2021-04-26 09:41:15 -07:00
events	Merge branch 'for-v5.13-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2021-05-21 06:12:52 -10:00
gcov	gcov: clang: drop support for clang-10 and older	2021-05-07 00:26:32 -07:00
irq	gpio updates for v5.13	2021-05-05 12:39:29 -07:00
kcsan	kcsan: Fix debugfs initcall return type	2021-05-18 10:58:02 -07:00
livepatch	Livepatching changes for 5.13	2021-04-27 18:14:38 -07:00
locking	locking/qrwlock: Cleanup queued_write_lock_slowpath()	2021-05-06 15:33:49 +02:00
power	PM: sleep: fix typos in comments	2021-04-08 19:37:21 +02:00
printk	kernel/printk.c: Fixed mundane typos	2021-03-30 15:34:17 +02:00
rcu	Merge branches 'bitmaprange.2021.03.08a', 'fixes.2021.03.15a', 'kvfree_rcu.2021.03.08a', 'mmdumpobj.2021.03.08a', 'nocb.2021.03.15a', 'poll.2021.03.24a', 'rt.2021.03.08a', 'tasks.2021.03.08a', 'torture.2021.03.08a' and 'torturescript.2021.03.22a' into HEAD	2021-03-24 17:20:18 -07:00
sched	sched/fair: Fix clearing of has_idle_cores flag in select_idle_cpu()	2021-05-12 10:41:28 +02:00
time	alarmtimer: Check RTC features instead of ops	2021-05-11 21:28:04 +02:00
trace	tracing: Handle %.*s in trace_check_vprintf()	2021-05-13 14:20:33 -04:00
.gitignore	.gitignore: prefix local generated files with a slash	2021-05-02 00:43:35 +09:00
acct.c	kernel/acct.c: use #elif instead of #end and #elif	2020-12-15 22:46:15 -08:00
async.c	kernel/async.c: remove async_unregister_domain()	2021-05-07 00:26:33 -07:00
audit_fsnotify.c	audit_alloc_mark(): don't open-code ERR_CAST()	2021-02-23 10:25:27 -05:00
audit_tree.c	fsnotify: generalize handle_inode_event()	2020-12-03 14:58:35 +01:00
audit_watch.c	fsnotify: generalize handle_inode_event()	2020-12-03 14:58:35 +01:00
audit.c	lsm: separate security_task_getsecid() into subjective and objective variants	2021-03-22 15:23:32 -04:00
audit.h	audit: avoid -Wempty-body warning	2021-03-24 12:11:48 -04:00
auditfilter.c	lsm: separate security_task_getsecid() into subjective and objective variants	2021-03-22 15:23:32 -04:00
auditsc.c	audit/stable-5.13 PR 20210426	2021-04-27 13:50:58 -07:00
backtracetest.c
bounds.c
capability.c	capability: handle idmapped mounts	2021-01-24 14:27:16 +01:00
cfi.c	add support for Clang CFI	2021-04-08 16:04:20 -07:00
compat.c
configs.c
context_tracking.c
cpu_pm.c
cpu.c	cpumask/hotplug: Fix cpu_dying() state tracking	2021-04-21 13:55:43 +02:00
crash_core.c	kdump: append uts_namespace.name offset to VMCOREINFO	2020-12-15 22:46:18 -08:00
crash_dump.c
cred.c	kernel/cred.c: make init_groups static	2021-05-06 19:24:11 -07:00
delayacct.c
dma.c
exec_domain.c
exit.c	do_wait: make PIDTYPE_PID case O(1) instead of O(n)	2021-05-06 19:24:13 -07:00
extable.c
fail_function.c	fault-injection: handle EI_ETYPE_TRUE	2020-12-15 22:46:19 -08:00
fork.c	kernel/fork.c: fix typos	2021-05-06 19:24:13 -07:00
freezer.c	Revert "kernel: freezer should treat PF_IO_WORKER like PF_KTHREAD for freezing"	2021-03-27 14:09:10 -06:00
futex.c	futex: Make syscall entry points less convoluted	2021-05-06 20:19:04 +02:00
gen_kheaders.sh	kbuild: redo fake deps at include/config/*.h	2021-04-25 05:26:10 +09:00
groups.c	groups: simplify struct group_info allocation	2021-02-26 09:41:03 -08:00
hung_task.c
iomem.c
irq_work.c	irq_work: record irq_work_queue() call stack	2021-04-30 11:20:42 -07:00
jump_label.c	static_call: Fix static_call_update() sanity check	2021-03-19 13:16:44 +01:00
kallsyms.c	kallsyms: strip ThinLTO hashes from static functions	2021-04-08 16:04:21 -07:00
kcmp.c	Merge branch 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2020-12-15 19:36:48 -08:00
Kconfig.freezer
Kconfig.hz
Kconfig.locks
Kconfig.preempt	preempt: Introduce CONFIG_PREEMPT_DYNAMIC	2021-02-17 14:12:24 +01:00
kcov.c
kexec_core.c	kexec: dump kmessage before machine_kexec	2021-05-07 00:26:32 -07:00
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: move machine_kexec_post_load() to public interface	2021-02-22 12:33:26 +00:00
kexec.c
kheaders.c
kmod.c	modules: add CONFIG_MODPROBE_PATH	2021-05-07 00:26:33 -07:00
kprobes.c	kprobes: Fix to delay the kprobes jump optimization	2021-02-19 14:57:12 -05:00
ksysfs.c
kthread.c	Scheduler updates for this cycle are:	2021-04-28 13:33:57 -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: harden ELF info handling	2021-01-19 10:24:45 +01:00
module_signing.c	module: harden ELF info handling	2021-01-19 10:24:45 +01:00
module-internal.h
module.c	module: check for exit sections in layout_sections() instead of module_init_section()	2021-05-17 09:48:24 +02:00
notifier.c
nsproxy.c	fixes-v5.11	2020-12-14 16:40:27 -08:00
padata.c
panic.c	panic: don't dump stack twice on warn	2020-11-14 11:26:04 -08:00
params.c	Modules updates for v5.11	2020-12-17 13:01:31 -08:00
pid_namespace.c	fixes-v5.11	2020-12-14 16:40:27 -08:00
pid.c	Merge branch 'exec-update-lock-for-v5.11' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2020-12-15 19:36:48 -08:00
profile.c	kernel: Initialize cpumask before parsing	2021-04-10 13:35:54 +02:00
ptrace.c	ptrace: make ptrace() fail if the tracee changed its pid unexpectedly	2021-05-12 10:45:22 -07:00
range.c
reboot.c	Revert "PM: ACPI: reboot: Use S5 for reboot"	2021-03-18 16:58:02 +01:00
regset.c
relay.c	relay: allow the use of const callback structs	2020-12-15 22:46:18 -08:00
resource_kunit.c	resource: provide meaningful MODULE_LICENSE() in test suite	2020-11-25 18:52:35 +01:00
resource.c	kernel/resource: fix return code check in __request_free_mem_region	2021-05-14 19:41:32 -07:00
rseq.c	rseq: Optimise rseq_get_rseq_cs() and clear_rseq_cs()	2021-04-14 18:04:09 +02:00
scftorture.c	scftorture: Add debug output for wrong-CPU warning	2021-01-04 13:53:41 -08:00
scs.c	scs: switch to vmapped shadow stacks	2020-12-01 10:30:28 +00:00
seccomp.c	Merge branch 'work.file' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2021-05-03 11:05:28 -07:00
signal.c	Merge branch 'for-v5.13-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace	2021-05-21 06:12:52 -10:00
smp.c	smp: Fix smp_call_function_single_async prototype	2021-05-06 15:33:49 +02:00
smpboot.c	kthread: Extract KTHREAD_IS_PER_CPU	2021-01-22 15:09:42 +01:00
smpboot.h
softirq.c	RCU changes for this cycle were:	2021-04-28 12:00:13 -07:00
stackleak.c
stacktrace.c
static_call.c	static_call: Fix unused variable warn w/o MODULE	2021-04-09 13:22:12 +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	Add Landlock, a new LSM from Mickaël Salaün <mic@linux.microsoft.com>	2021-05-01 18:50:44 -07:00
sys.c	kernel/sys.c: fix typo	2021-05-07 00:26:34 -07:00
sysctl-test.c
sysctl.c	mm/compaction: remove unused variable sysctl_compact_memory	2021-05-05 11:27:24 -07:00
task_work.c	kasan: record task_work_add() call stack	2021-04-30 11:20:42 -07:00
taskstats.c	treewide: rename nla_strlcpy to nla_strscpy.	2020-11-16 08:08:54 -08:00
test_kprobes.c
torture.c	torture: Replace torture_init_begin string with %s	2021-03-08 14:22:28 -08:00
tracepoint.c	tracepoints: Code clean up	2021-02-09 12:27:29 -05:00
tsacct.c
ucount.c	fanotify: configurable limits via sysfs	2021-03-16 16:49:31 +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	kernel/user_namespace.c: fix typos	2021-05-07 00:26:34 -07:00
user-return-notifier.c
user.c
usermode_driver.c	bpf: Fix umd memory leak in copy_process()	2021-03-19 22:23:19 +01:00
utsname_sysctl.c
utsname.c
watch_queue.c	watch_queue: rectify kernel-doc for init_watch()	2021-01-26 11:16:34 +00:00
watchdog_hld.c
watchdog.c	watchdog: reliable handling of timestamps	2021-05-22 15:09:07 -10:00
workqueue_internal.h
workqueue.c	CFI on arm64 series for v5.13-rc1	2021-04-27 10:16:46 -07:00