The commit 719f6a7040f1bdaf96 ("printk: Use the main logbuf in NMI
when logbuf_lock is available") brought back the possible deadlocks
in printk() and NMI.
This is rework of the proposed fix, see
https://lkml.kernel.org/r/20180606111557.xzs6l3lkvg7lq3ts@xxxxxxxxxxxxxxx
I realized that we could rather easily move the check to vprintk_func()
and still avoid any race. I believe that this is a win-win solution.
Changes against v1:
+ Move the check from vprintk_emit() to vprintk_func()
+ More straightforward commit message
+ Fix build with CONFIG_PRINTK_NMI disabled
Petr Mladek (3):
printk: Split the code for storing a message into the log buffer
printk: Create helper function to queue deferred console handling
printk/nmi: Prevent deadlock when accessing the main log buffer in NMI
include/linux/printk.h | 4 ++++
kernel/printk/internal.h | 9 ++++++-
kernel/printk/printk.c | 57 +++++++++++++++++++++++++++-----------------
kernel/printk/printk_safe.c | 58 +++++++++++++++++++++++++++++----------------
kernel/trace/trace.c | 4 +++-
lib/nmi_backtrace.c | 3 ---
6 files changed, 87 insertions(+), 48 deletions(-)
--
2.13.7
