[PATCH next v1 0/2] introduce printk cpu lock

[John Ogness]

While working on removing the safe buffers for printk [0] we
stumbled on a cpu-reentrant spinning lock used by dump_stack(). This
type of lock (dubbed a cpu lock) will cause deadlock risks once we
introduce atomic consoles because atomic consoles also need such a
lock.

Although we are not yet ready to introduce atomic consoles, this is
an appropriate time to provide an official cpu lock to be used for
all things relating to printk (including the atomic consoles, once
they are introduced).

This series also extends the new printk cpu lock to cover
show_regs().

This series is against next-20210528.

John Ogness

[0] https://lore.kernel.org/lkml/YGW63%2FelFr%2FgYW1u@alley

John Ogness (2):
  dump_stack: move cpu lock to printk.c
  nmi_backtrace: use the printk cpu lock for show_regs()

 include/linux/printk.h | 13 ++++++
 kernel/printk/printk.c | 92 ++++++++++++++++++++++++++++++++++++++++++
 lib/dump_stack.c       | 43 ++------------------
 lib/nmi_backtrace.c    |  4 ++
 4 files changed, 112 insertions(+), 40 deletions(-)

-- 
2.20.1