lkml.org 
[lkml]   [2008]   [Jun]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] add a printk_init variant storing format strings in __initdata
    On Tue, 3 Jun 2008 10:27:32 +0100 Andy Whitcroft <apw@shadowen.org> wrote:

    >
    > [As gcc seems unable to help us out selecting the appropriate data segment
    > for the code, how about we did something like this?]
    >
    > When using printk from __init functions it would be desirable to place
    > the printk format strings in __initdata. Add a printk_init() variant
    > which does this.
    >
    > This printk_init() is necessarily a #define so that we can declare the
    > format string in static scope and mark it __initdata. We then call a
    > newly introduced __printk_init() variant which is identicle to printk() but
    > marked __init itself. By ensuring that an __init variant of printk is used
    > we get proper section violation warnings when this is used incorrectly:
    >
    > WARNING: vmlinux.o(.text+0x3): Section mismatch in reference from the
    > function something() to the variable .init.data:__printk_init_fmt.31426
    > The function something() references
    > the variable __initdata __printk_init_fmt.31426.
    > This is often because something lacks a __initdata
    > annotation or the annotation of __printk_init_fmt.31426 is wrong.
    >
    > Note I have followed printk's pattern for __cold annotations.
    >

    Ho hum. This give everyone another way in which to bury everyone else
    with patches.

    Wouldn't it be great if checkpatch were to detect
    fail-to-use-printk_init() in an __init function?

    oh, speaking of checkpatch: please use it :)

    > ---
    > include/linux/kernel.h | 10 ++++++++++
    > kernel/printk.c | 12 ++++++++++++
    > 2 files changed, 22 insertions(+), 0 deletions(-)
    > diff --git a/include/linux/kernel.h b/include/linux/kernel.h
    > index 792bf0a..7754196 100644
    > --- a/include/linux/kernel.h
    > +++ b/include/linux/kernel.h
    > @@ -180,6 +180,13 @@ struct pid;
    > extern struct pid *session_of_pgrp(struct pid *pgrp);
    >
    > #ifdef CONFIG_PRINTK
    > +#define printk_init(fmt, args...) \
    > +do { \
    > + static char __printk_init_fmt[] __initdata = fmt; \
    > + __printk_init(__printk_init_fmt, ##args); \
    > +} while (0)
    > +asmlinkage int __printk_init(const char * fmt, ...)
    > + __attribute__ ((format (printf, 1, 2))) __cold;
    > asmlinkage int vprintk(const char *fmt, va_list args)
    > __attribute__ ((format (printf, 1, 0)));
    > asmlinkage int printk(const char * fmt, ...)
    > @@ -196,6 +203,9 @@ extern int __printk_ratelimit(int ratelimit_jiffies, int ratelimit_burst);
    > extern bool printk_timed_ratelimit(unsigned long *caller_jiffies,
    > unsigned int interval_msec);
    > #else
    > +asmlinkage int printk_init(const char * fmt, ...)
    > + __attribute__ ((format (printf, 1, 2))) __cold;
    > +static inline int __cold printk_init(const char *s, ...) { return 0; }
    > static inline int vprintk(const char *s, va_list args)
    > __attribute__ ((format (printf, 1, 0)));
    > static inline int vprintk(const char *s, va_list args) { return 0; }
    > diff --git a/kernel/printk.c b/kernel/printk.c
    > index 8fb01c3..992a5c0 100644
    > --- a/kernel/printk.c
    > +++ b/kernel/printk.c
    > @@ -616,6 +616,18 @@ asmlinkage int printk(const char *fmt, ...)
    > return r;
    > }
    >
    > +asmlinkage __init int __printk_init(const char *fmt, ...)
    > +{
    > + va_list args;
    > + int r;
    > +
    > + va_start(args, fmt);
    > + r = vprintk(fmt, args);
    > + va_end(args);
    > +
    > + return r;
    > +}

    We're going to want to be able to call printk_init() from modules.
    Please fix and test that, if we decide to proceed.

    Oh, and we're going to need printk_meminit() and printk_cpuinit() and
    whatever.

    Which probably means that __printk_init() can't be __init, unless all
    the CONFIG_ settings which control __cpuinit, __meminit etc are blowing
    in the right direction.

    It would be good if we could get some idea of the savings here, because
    boy this is going to be a pain.



    \
     
     \ /
      Last update: 2008-06-04 10:21    [W:0.026 / U:0.660 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site