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commit85e3e7fbbbupstream. [This patch implements subset of original commit85e3e7fbbb("printk: remove NMI tracking") where commit1007843a91("mm/page_alloc: fix potential deadlock on zonelist_update_seq seqlock") depends on, for commit3d36424b3b("mm/page_alloc: fix race condition between build_all_zonelists and page allocation") was backported to stable.] All NMI contexts are handled the same as the safe context: store the message and defer printing. There is no need to have special NMI context tracking for this. Using in_nmi() is enough. There are several parts of the kernel that are manually calling into the printk NMI context tracking in order to cause general printk deferred printing: arch/arm/kernel/smp.c arch/powerpc/kexec/crash.c kernel/trace/trace.c For arm/kernel/smp.c and powerpc/kexec/crash.c, provide a new function pair printk_deferred_enter/exit that explicitly achieves the same objective. For ftrace, remove the printk context manipulation completely. It was added in commit03fc7f9c99("printk/nmi: Prevent deadlock when accessing the main log buffer in NMI"). The purpose was to enforce storing messages directly into the ring buffer even in NMI context. It really should have only modified the behavior in NMI context. There is no need for a special behavior any longer. All messages are always stored directly now. The console deferring is handled transparently in vprintk(). Signed-off-by: John Ogness <john.ogness@linutronix.de> [pmladek@suse.com: Remove special handling in ftrace.c completely. Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20210715193359.25946-5-john.ogness@linutronix.de [penguin-kernel: Copy only printk_deferred_{enter,safe}() definition ] Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.