On Wed 2018-06-27 16:08:14, Petr Mladek wrote:
> 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(-)
JFYI, I have renamed the new function defer_console() to
defer_console_output() and pushed everything to printk.git,
branch for-4.19-nmi.
Best Regards,
Petr
