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John Ogness 2bb2b7b57f printk: add functions to prefer direct printing 
Once kthread printing is available, console printing will no longer
occur in the context of the printk caller. However, there are some
special contexts where it is desirable for the printk caller to
directly print out kernel messages. Using pr_flush() to wait for
threaded printers is only possible if the caller is in a sleepable
context and the kthreads are active. That is not always the case.

Introduce printk_prefer_direct_enter() and printk_prefer_direct_exit()
functions to explicitly (and globally) activate/deactivate preferred
direct console printing. The term "direct console printing" refers to
printing to all enabled consoles from the context of the printk
caller. The term "prefer" is used because this type of printing is
only best effort. If the console is currently locked or other
printers are already actively printing, the printk caller will need
to rely on the other contexts to handle the printing.

This preferred direct printing is how all printing has been handled
until now (unless it was explicitly deferred).

When kthread printing is introduced, there may be some unanticipated
problems due to kthreads being unable to flush important messages.
In order to minimize such risks, preferred direct printing is
activated for the primary important messages when the system
experiences general types of major errors. These are:

 - emergency reboot/shutdown
 - cpu and rcu stalls
 - hard and soft lockups
 - hung tasks
 - warn
 - sysrq

Note that since kthread printing does not yet exist, no behavior
changes result from this commit. This is only implementing the
counter and marking the various places where preferred direct
printing is active.

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org> # for RCU
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20220421212250.565456-13-john.ogness@linutronix.de
2022-04-22 21:30:58 +02:00
..
bpf bpf: Add schedule points in batch ops 2022-02-17 10:48:26 -08:00
cgroup Linux 5.17-rc8 2022-03-15 10:28:12 +01:00
configs configs/debug: restore DEBUG_INFO=y for overriding 2022-03-17 11:02:13 -07:00
debug kdb: Adopt scheduler's task classification 2021-11-03 17:21:37 +00:00
dma cma: factor out minimum alignment requirement 2022-03-22 15:57:05 -07:00
entry Changes in this cycle were: 2022-03-22 14:39:12 -07:00
events Folio changes for 5.18 2022-03-22 17:03:12 -07:00
futex mm/truncate: Inline invalidate_complete_page() into its one caller 2022-03-21 12:59:01 -04:00
gcov gcov: Remove compiler version check 2021-12-02 17:25:21 +09:00
irq Changes in this cycle were: 2022-03-22 14:39:12 -07:00
kcsan KCSAN updates for v5.17 2022-01-11 09:51:26 -08:00
livepatch Livepatching changes for 5.17 2022-01-16 10:08:13 +02:00
locking Changes in this cycle were: 2022-03-22 13:44:21 -07:00
power for-5.18/block-2022-03-18 2022-03-21 16:48:55 -07:00
printk printk: add functions to prefer direct printing 2022-04-22 21:30:58 +02:00
rcu printk: add functions to prefer direct printing 2022-04-22 21:30:58 +02:00
sched Merge branch 'akpm' (patches from Andrew) 2022-03-22 16:11:53 -07:00
time tick/rcu: Stop allowing RCU_SOFTIRQ in idle 2022-03-07 23:01:34 +01:00
trace Changes in this cycle were: 2022-03-22 14:39:12 -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/stable-5.18 PR 20220321 2022-03-21 20:53:11 -07:00
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 Changes in this cycle were: 2022-03-22 14:39:12 -07:00
crash_core.c kernel/crash_core: suppress unknown crashkernel parameter warning 2021-12-25 12:20:55 -08:00
crash_dump.c
cred.c ucounts: Base set_cred_ucounts changes on the real user 2022-02-17 09:11:02 -06:00
delayacct.c delayacct: track delays from memory compact 2022-01-20 08:52:55 +02:00
dma.c
exec_domain.c
exit.c for-5.18/block-2022-03-18 2022-03-21 16:48:55 -07:00
extable.c extable: use is_kernel_text() helper 2021-11-09 10:02:51 -08:00
fail_function.c
fork.c Core code updates: 2022-03-21 12:37:33 -07:00
freezer.c sched: Add get_current_state() 2021-06-18 11:43:08 +02:00
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: Also rcuwait for !IRQ_WORK_HARD_IRQ on PREEMPT_RT 2021-10-15 11:25:18 +02:00
jump_label.c jump_label: Fix jump_label_text_reserved() vs __init 2021-07-05 10:46:20 +02:00
kallsyms.c Livepatching changes for 5.17 2022-01-16 10:08:13 +02:00
kcmp.c
Kconfig.freezer
Kconfig.hz
Kconfig.locks locking/rwlock: Provide RT variant 2021-08-17 17:50:51 +02:00
Kconfig.preempt Changes in this cycle were: 2022-03-22 14:39:12 -07:00
kcov.c kcov: replace local_irq_save() with a local_lock_t 2021-11-09 10:02:52 -08:00
kexec_core.c exit: Move oops specific logic from do_exit into make_task_dead 2021-12-13 12:04:45 -06:00
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 kprobe: move sysctl_kprobes_optimization to kprobes.c 2022-01-22 08:33:36 +02:00
ksysfs.c
kthread.c sched/isolation: Use single feature type while referring to housekeeping cpumask 2022-02-16 15:57:55 +01:00
latencytop.c
Makefile module: add in-kernel support for decompressing 2022-01-11 18:45:02 -08:00
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: add functions to prefer direct printing 2022-04-22 21:30:58 +02:00
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: Remove second setting of PT_SEIZED in ptrace_attach 2022-01-08 12:43:57 -06:00
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 proc: remove PDE_DATA() completely 2022-01-22 08:33:37 +02:00
rseq.c rseq: Remove broken uapi field layout on 32-bit little endian 2022-02-02 13:11:34 +01:00
scftorture.c scftorture: Always log error message 2021-12-07 16:36:17 -08:00
scs.c scs: Release kasan vmalloc poison in scs_free process 2021-09-30 09:37:27 +01:00
seccomp.c seccomp: Invalidate seccomp mode to catch death failures 2022-02-10 19:09:12 -08:00
signal.c signal, x86: Delay calling signals in atomic on RT enabled kernels 2022-03-04 14:58:54 +01:00
smp.c sched: Improve wake_up_all_idle_cpus() take #2 2021-10-22 15:32:46 +02:00
smpboot.c smpboot: Replace deprecated CPU-hotplug functions. 2021-08-10 14:57:42 +02:00
smpboot.h
softirq.c genirq, softirq: Use in_hardirq() instead of in_irq() 2022-02-02 21:34:19 +01:00
stackleak.c gcc-plugins/stackleak: Use noinstr in favor of notrace 2022-02-03 17:02:21 -08:00
stacktrace.c stacktrace: move filter_irq_stacks() to kernel/stacktrace.c 2021-11-06 13:30:43 -07:00
static_call.c static_call: Fix static_call_text_reserved() vs __init 2021-07-05 10:46:33 +02:00
stop_machine.c
sys_ni.c mm/mempolicy: wire up syscall set_mempolicy_home_node 2022-01-15 16:30:30 +02:00
sys.c mm: refactor vm_area_struct::anon_vma_name usage code 2022-03-05 11:08:32 -08:00
sysctl-test.c kernel/sysctl-test: Remove some casts which are no-longer required 2021-06-23 16:41:24 -06:00
sysctl.c Merge branch 'akpm' (patches from Andrew) 2022-03-22 16:11:53 -07:00
task_work.c
taskstats.c
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 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 2022-03-21 12:48:32 +00:00
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 sched/isolation: Use single feature type while referring to housekeeping cpumask 2022-02-16 15:57:55 +01:00