Petr Mladek c3230283e2 printk: Block console kthreads when direct printing will be required ... There are known situations when the console kthreads are not reliable or does not work in principle, for example, early boot, panic, shutdown. For these situations there is the direct (legacy) mode when printk() tries to get console_lock() and flush the messages directly. It works very well during the early boot when the console kthreads are not available at all. It gets more complicated in the other situations when console kthreads might be actively printing and block console_trylock() in printk(). The same problem is in the legacy code as well. Any console_lock() owner could block console_trylock() in printk(). It is solved by a trick that the current console_lock() owner is responsible for printing all pending messages. It is actually the reason why there is the risk of softlockups and why the console kthreads were introduced. The console kthreads use the same approach. They are responsible for printing the messages by definition. So that they handle the messages anytime when they are awake and see new ones. The global console_lock is available when there is nothing to do. It should work well when the problematic context is correctly detected and printk() switches to the direct mode. But it seems that it is not enough in practice. There are reports that the messages are not printed during panic() or shutdown() even though printk() tries to use the direct mode here. The problem seems to be that console kthreads become active in these situation as well. They steel the job before other CPUs are stopped. Then they are stopped in the middle of the job and block the global console_lock. First part of the solution is to block console kthreads when the system is in a problematic state and requires the direct printk() mode. Link: https://lore.kernel.org/r/20220610205038.GA3050413@paulmck-ThinkPad-P17-Gen-1 Link: https://lore.kernel.org/r/CAMdYzYpF4FNTBPZsEFeWRuEwSies36QM_As8osPWZSr2q-viEA@mail.gmail.com Suggested-by: John Ogness <john.ogness@linutronix.de> Tested-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20220615162805.27962-2-pmladek@suse.com		2022-06-15 22:03:38 +02:00
..
bpf	rcu: Make the TASKS_RCU Kconfig option be selected	2022-04-20 16:52:58 -07:00
cgroup	cgroup/cpuset: Remove cpus_allowed/mems_allowed setup in cpuset_init_smp()	2022-05-05 08:57:00 -10:00
configs	x86/configs: Add x86 debugging Kconfig fragment plus docs	2022-04-06 19:56:29 +02:00
debug	lockdown: also lock down previous kgdb use	2022-05-24 11:29:34 -07:00
dma	dma-direct: avoid redundant memory sync for swiotlb	2022-04-14 06:30:39 +02:00
entry	Locking changes in this cycle were:	2022-05-24 10:18:23 -07:00
events	Page cache changes for 5.19	2022-05-24 19:55:07 -07:00
futex	futex: Remove a PREEMPT_RT_FULL reference.	2022-05-13 12:36:51 +02:00
gcov	gcov: Remove compiler version check	2021-12-02 17:25:21 +09:00
irq	Updates for interrupt core and drivers:	2022-05-23 16:58:49 -07:00
kcsan	kcsan: Use preemption model accessors	2022-04-05 10:24:42 +02:00
livepatch	ptrace: Cleanups for v5.18	2022-03-28 17:29:53 -07:00
locking	locking/qrwlock: Change "queue rwlock" to "queued rwlock"	2022-05-11 16:27:04 +02:00
power	Merge branches 'pm-em' and 'pm-cpuidle'	2022-05-23 19:18:51 +02:00
printk	printk: Block console kthreads when direct printing will be required	2022-06-15 22:03:38 +02:00
rcu	printk changes for 5.19	2022-05-25 10:32:08 -07:00
sched	Scheduler changes in this cycle were:	2022-05-24 11:11:13 -07:00
time	Random number generator updates for Linux 5.19-rc1.	2022-05-24 11:58:10 -07:00
trace	Scheduler changes in this cycle were:	2022-05-24 11:11:13 -07:00
.gitignore
acct.c	kernel: remove spurious blkdev.h includes	2021-10-18 06:17:01 -06:00
async.c	Revert "module, async: async_synchronize_full() on module init iff async is used"	2022-02-03 11:20:34 -08:00
audit_fsnotify.c	fsnotify: clarify contract for create event hooks	2021-10-27 12:32:34 +02:00
audit_tree.c	audit: use struct_size() helper in kmalloc()	2021-12-14 17:39:42 -05:00
audit_watch.c	\n	2021-11-06 16:43:20 -07:00
audit.c	audit: improve audit queue handling when "audit=1" on cmdline	2022-01-25 13:22:51 -05:00
audit.h	audit: log AUDIT_TIME_* records only from rules	2022-02-22 13:51:40 -05:00
auditfilter.c	audit/stable-5.17 PR 20220110	2022-01-11 13:08:21 -08:00
auditsc.c	audit,io_uring,io-wq: call __audit_uring_exit for dummy contexts	2022-05-17 15:03:36 -04:00
backtracetest.c
bounds.c
capability.c	xfs: don't generate selinux audit messages for capability testing	2022-03-09 10:32:06 -08:00
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	Intel Trust Domain Extensions	2022-05-23 17:51:12 -07:00
crash_core.c	kdump: return -ENOENT if required cmdline option does not exist	2022-05-07 19:54:33 +01:00
crash_dump.c
cred.c	x86: Mark __invalid_creds() __noreturn	2022-03-15 10:32:44 +01:00
delayacct.c	delayacct: track delays from memory compact	2022-01-20 08:52:55 +02:00
dma.c
exec_domain.c
exit.c	ptrace: Cleanups for v5.18	2022-03-28 17:29:53 -07:00
extable.c	lkdtm: Really write into kernel text in WRITE_KERN	2022-02-16 23:25:12 +11:00
fail_function.c
fork.c	- Add Raptor Lake to the set of CPU models which support splitlock	2022-05-23 19:24:47 -07:00
freezer.c
gen_kheaders.sh
groups.c
hung_task.c	printk: add functions to prefer direct printing	2022-04-22 21:30:58 +02:00
iomem.c
irq_work.c	irq_work: use kasan_record_aux_stack_noalloc() record callstack	2022-04-15 14:49:55 -07:00
jump_label.c
kallsyms.c	kallsyms: Skip the name search for empty string	2022-03-17 20:17:18 -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	Revert "signal, x86: Delay calling signals in atomic on RT enabled kernels"	2022-03-31 10:36:55 +02:00
kcov.c	kcov: don't generate a warning on vm_insert_page()'s failure	2022-04-21 20:01:10 -07:00
kexec_core.c	ELF: Remove elf_core_copy_kernel_regs()	2022-04-14 14:08:26 +02:00
kexec_elf.c
kexec_file.c	memblock: add MEMBLOCK_DRIVER_MANAGED to mimic IORESOURCE_SYSRAM_DRIVER_MANAGED	2021-11-06 13:30:42 -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
kprobes.c	kprobes: Fix KRETPROBES when CONFIG_KRETPROBE_ON_RETHOOK is set	2022-04-26 16:09:36 +02:00
ksysfs.c	kernel/ksysfs.c: use helper macro __ATTR_RW	2022-03-23 19:00:33 -07:00
kthread.c	kthread: unexport kthread_blkcg	2022-05-02 14:06:20 -06:00
latencytop.c
Makefile	static_call: Don't make __static_call_return0 static	2022-04-05 09:59:38 +02:00
module_decompress.c	module: fix building with sysfs disabled	2022-02-16 12:51:32 -08:00
module_signature.c
module_signing.c
module-internal.h	module: add in-kernel support for decompressing	2022-01-11 18:45:02 -08:00
module.c	NFSD: Remove svc_serv_ops::svo_module	2022-02-28 10:26:40 -05:00
notifier.c	notifier: Return an error when a callback has already been registered	2021-12-29 10:37:33 +01:00
nsproxy.c	memcg: enable accounting for new namesapces and struct nsproxy	2021-09-03 09:58:12 -07:00
padata.c	padata: replace cpumask_weight with cpumask_empty in padata.c	2022-01-31 11:21:46 +11:00
panic.c	printk changes for 5.19	2022-05-25 10:32:08 -07:00
params.c	kobject: remove kset from struct kset_uevent_ops callbacks	2021-12-28 11:26:18 +01:00
pid_namespace.c	memcg: enable accounting for new namesapces and struct nsproxy	2021-09-03 09:58:12 -07:00
pid.c	pid: add pidfd_get_task() helper	2021-10-14 13:29:18 +02:00
profile.c	exit: Remove profile_handoff_task	2022-01-08 12:43:57 -06:00
ptrace.c	ptrace: Check PTRACE_O_SUSPEND_SECCOMP permission on PTRACE_SEIZE	2022-03-22 13:06:05 -05:00
range.c
reboot.c	printk: add functions to prefer direct printing	2022-04-22 21:30:58 +02:00
regset.c
relay.c
resource_kunit.c
resource.c	kernel/resource: fix kfree() of bootmem memory again	2022-03-23 19:00:35 -07:00
rseq.c	rseq: Remove broken uapi field layout on 32-bit little endian	2022-02-02 13:11:34 +01:00
scftorture.c	scftorture: Fix distribution of short handler delays	2022-04-11 17:07:29 -07:00
scs.c	kasan, vmalloc: only tag normal vmalloc allocations	2022-03-24 19:06:48 -07:00
seccomp.c	seccomp: Add wait_killable semantic to seccomp user notifier	2022-05-03 14:11:58 -07:00
signal.c	signal: Deliver SIGTRAP on perf event asynchronously if blocked	2022-04-22 12:14:05 +02:00
smp.c	Scheduler changes in this cycle were:	2022-05-24 11:11:13 -07:00
smpboot.c	cpu/hotplug: Allow the CPU in CPU_UP_PREPARE state to be brought up again.	2022-04-12 14:13:01 +02:00
smpboot.h
softirq.c	smp: Make softirq handling RT safe in flush_smp_call_function_queue()	2022-05-01 10:03:43 +02:00
stackleak.c	stackleak: add on/off stack variants	2022-05-08 01:33:09 -07:00
stacktrace.c	uaccess: remove CONFIG_SET_FS	2022-02-25 09:36:06 +01:00
static_call_inline.c	static_call: Don't make __static_call_return0 static	2022-04-05 09:59:38 +02:00
static_call.c	static_call: Don't make __static_call_return0 static	2022-04-05 09:59:38 +02:00
stop_machine.c	Scheduler changes in this cycle were:	2022-05-24 11:11:13 -07:00
sys_ni.c	mm/mempolicy: wire up syscall set_mempolicy_home_node	2022-01-15 16:30:30 +02:00
sys.c	arm64/sme: Implement vector length configuration prctl()s	2022-04-22 18:50:54 +01:00
sysctl-test.c
sysctl.c	timers: Move timer sysctl into the timer code	2022-04-10 12:38:45 +02:00
task_work.c	task_work: allow TWA_SIGNAL without a rescheduling IPI	2022-04-30 08:39:32 -06:00
taskstats.c	taskstats: remove unneeded dead assignment	2022-03-23 19:00:35 -07:00
torture.c	torture: Wake up kthreads after storing task_struct pointer	2022-02-01 17:24:39 -08:00
tracepoint.c	tracepoint: Fix kerneldoc comments	2021-08-16 11:39:51 -04:00
tsacct.c	taskstats: Cleanup the use of task->exit_code	2022-01-08 12:43:57 -06:00
ucount.c	ucounts: Handle wrapping in is_ucounts_overlimit	2022-02-17 09:11:57 -06:00
uid16.c
uid16.h
umh.c
up.c
user_namespace.c	ucounts: Fix systemd LimitNPROC with private users regression	2022-02-25 10:40:14 -06:00
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
utsname_sysctl.c
utsname.c
watch_queue.c	watch_queue: Free the page array when watch_queue is dismantled	2022-04-02 10:37:39 -07:00
watchdog_hld.c	printk: add functions to prefer direct printing	2022-04-22 21:30:58 +02:00
watchdog.c	printk: add functions to prefer direct printing	2022-04-22 21:30:58 +02:00
workqueue_internal.h	workqueue: Assign a color to barrier work items	2021-08-17 07:49:10 -10:00
workqueue.c	Merge branch 'for-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq	2022-03-23 12:40:51 -07:00