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Moving enabling of function tracing to early boot, even before scheduling is enabled, means that it is not safe to enable interrupts. When function tracing was enabled at boot up, it use to happen after scheduling and the other CPUs were brought up. That required running a sync across all CPUs when modifying the function hook locations in the code. To do the synchronization, interrupts had to be enabled. Now function tracing can be started before the other CPUs are brought up, and enabling interrupts in that case is dangerous. As only tho boot CPU is active, there is no reason to run the synchronization. If the online CPU count is one, do not bother doing the synchronization. This removes the need to enable interrupts. Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.