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    Subject[PATCH 07/10] dynamic debug: resurrect old pr_debug() semantics as pr_devel()
    Date
    From: Michael Ellerman <michael@ellerman.id.au>

    pr_debug() used to produce zero code unless DEBUG was #defined. This is
    now no longer the case in practice[1].

    There are places where it's useful to have debugging printks, but we don't
    want them to generate any code in production kernels.

    So add a new macro, pr_devel(), for _devel_opment, to provide the old
    semantics, ie. if the programmer doesn't explicitly enable debugging, no
    code is produced.

    [1]: You can turn CONFIG_DYNAMIC_DEBUG off, but it's enabled in at least
    one distro kernel, so it's not really a solution.

    Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
    Cc: Jason Baron <jbaron@redhat.com>
    Cc: Greg Banks <gnb@sgi.com>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    include/linux/kernel.h | 9 +++++++++
    1 files changed, 9 insertions(+), 0 deletions(-)

    diff --git a/include/linux/kernel.h b/include/linux/kernel.h
    index d9e75ec..883cd44 100644
    --- a/include/linux/kernel.h
    +++ b/include/linux/kernel.h
    @@ -377,6 +377,15 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
    #define pr_cont(fmt, ...) \
    printk(KERN_CONT fmt, ##__VA_ARGS__)

    +/* pr_devel() should produce zero code unless DEBUG is defined */
    +#ifdef DEBUG
    +#define pr_devel(fmt, ...) \
    + printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
    +#else
    +#define pr_devel(fmt, ...) \
    + ({ if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); 0; })
    +#endif
    +
    /* If you are writing a driver, please use dev_dbg instead */
    #if defined(DEBUG)
    #define pr_debug(fmt, ...) \
    --
    1.6.2


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