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Subject[RFC][PATCHv2 0/8] printk: introduce printing kernel thread


This patch set adds a printk() kernel thread which lets us to
print kernel messages to the console from a non-atomic/schedule-able
context, avoiding different sort of lockups, stalls, etc.

The biggest difference compared to v1 is a further expansion of
"switch to old printk() mode", which we now call printk_emergency mode,
annotations (pm, kexec, sysrq).

We also have a bunch of other ideas to try out/consider (not in
this patch set). E.g. automatic printk_emergency switch on printk_kthread
stalls (when we can't run printk_kthread), moving klogd irq_work out of
per-CPU memory, and so on.

-- introduce printk_emergency mode and API to switch it on/off
-- move printk_pending out of per-CPU memory
-- add printk emergency_mode sysfs node
-- switch sysrq handlers (some of them) to printk_emergency
-- cleanus/etc.

Sergey Senozhatsky (8):
printk: move printk_pending out of per-cpu
printk: introduce printing kernel thread
printk: offload printing from wake_up_klogd_work_func()
pm: switch to printk.emergency mode in unsafe places
sysrq: switch to printk.emergency mode in unsafe places
kexec: switch to printk.emergency mode in unsafe places
printk: add printk emergency_mode parameter
printk: enable printk offloading

drivers/tty/sysrq.c | 7 ++
include/linux/console.h | 3 +
kernel/kexec_core.c | 4 ++
kernel/power/hibernate.c | 8 +++
kernel/power/suspend.c | 4 ++
kernel/printk/printk.c | 178 +++++++++++++++++++++++++++++++++++++++++------
6 files changed, 182 insertions(+), 22 deletions(-)


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