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    SubjectRe: [PATCH 02/21] ftrace.c: Add #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
    On Mon, 2009-10-05 at 09:10 -0400, Steven Rostedt wrote:
    > On Sun, 2009-10-04 at 17:53 -0700, Joe Perches wrote:
    > > Remove prefixes from pr_<level>, use pr_fmt(fmt)
    > > No change in output.
    > What does KBUILD_MODNAME give us in the core code? This file does not
    > belong to any module and is only compiled into the core kernel.

    Hi Steven.

    KBUILD_MODNAME is basename(__FILE__), or if multiple files are
    grouped in the Makefile, then it's the basename(group)

    For ftrace.c, it gives "ftrace", which is the same
    as the prefix you were using, so there's no change
    in the output.

    For other entries in say kernel/power, there were
    messages that did not have prefixes

    I believe these are some of the +/-'s of each approach:


    o Allows some messages to not have a prefix at all
    o Prefixes can vary inside a specific compilation unit


    o Consistent, smaller source code, with no typos
    for instance: acpi/apic typos were found/fixed
    kernel/power had messages without PM:
    mce used "MCE: " and "mce: " prefixes
    o Compatible with KMSG_COMPONENT
    o All logging messages should have a prefix so
    it could be easier to grep/categorize logs
    o Future:
    - Doesn't require each compilation unit to #define pr_fmt
    - Smaller objects without duplicated prefixes
    - Extensible via some dynamic_debug like mechanism
    to hide or show modname/__func__/offset without
    significant overhead or any increase in object size
    (printk would emit the prefix via some insertion
    mechanism after "<level>")

    cheers, Joe

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