Sebastian Siewior
11e11d0a7d
Safe mode disables interrupts in order to minimize the window where printk calls use deferred printing. Currently local_irq_save() is used for this, however on PREEMPT_RT this can lead to large latencies because safe mode is enabled for the duration of printing a record. Use a local_lock instead of local_irq_save(). For !PREEMPT_RT it has the same affect of disabling interrupts for that CPU. For PREEMPT_RT it will disable preemption, which is enough to prevent interruption from the irq threads. Note that disabling preemption for PREEMPT_RT is also very bad since it is still blocking RT tasks. The atomic/threaded (NOBKL) consoles were developed such that safe mode is not needed. So it is expected that a PREEMPT_RT machine does not run with any legacy consoles registered. Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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.