mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-05-01 02:32:49 -04:00
e012c49998
The printk layer at the moment does not seem to have a good way to force
flush printk messages that are created in NMI context, except in the
panic path.
NMI-context printk messages normally get to the console with irq_work,
but that won't help if the CPU is stuck with irqs disabled, as can be
the case for hard lockup watchdog messages.
The watchdog currently flushes the printk buffers after detecting a
lockup on remote CPUs, but they may not have processed their NMI IPI
yet by that stage, or they may have self-detected a lockup in which
case they won't go via this NMI IPI path.
Improve the situation by having NMI-context mark a flag if it called
printk, and have watchdog timer interrupts check if that flag was set
and try to flush if it was. Latency is not a big problem because we
were already stuck for a while, just need to try to make sure the
messages eventually make it out.
Depends-on: 5d5e4522a7 ("printk: restore flushing of NMI buffers on remote CPUs after NMI backtraces")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211119113146.752759-6-npiggin@gmail.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.