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    SubjectRe: [PATCH -v3 6/7] kexec jump: __ftrace_enabled_save/restore
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    On Tue, 2008-08-12 at 09:06 -0400, Vivek Goyal wrote:
    > On Tue, Aug 12, 2008 at 11:14:36AM +0800, Huang Ying wrote:
    > > Add __ftrace_enabled_save/restore, used to disable ftrace for a
    > > while. Now, this is used by kexec jump, which need a version without
    > > lock, for general situation, a locked version should be used.
    > >
    > > Signed-off-by: Huang Ying <ying.huang@intel.com>
    > >
    > > ---
    > > include/linux/ftrace.h | 21 +++++++++++++++++++++
    > > 1 file changed, 21 insertions(+)
    > >
    > > --- a/include/linux/ftrace.h
    > > +++ b/include/linux/ftrace.h
    > > @@ -98,6 +98,27 @@ static inline void tracer_disable(void)
    > > #endif
    > > }
    > >
    > > +/* Ftrace disable/restore without lock. Some synchronization mechanism
    > > + * must be used to prevent ftrace_enabled to be changed between
    > > + * disable/restore. */
    > > +static inline int __ftrace_enabled_save(void)
    > > +{
    > > +#ifdef CONFIG_FTRACE
    > > + int saved_ftrace_enabled = ftrace_enabled;
    > > + ftrace_enabled = 0;
    > > + return saved_ftrace_enabled;
    > > +#else
    > > + return 0;
    > > +#endif
    > > +}
    > > +
    > > +static inline void __ftrace_enabled_restore(int enabled)
    > > +{
    > > +#ifdef CONFIG_FTRACE
    > > + ftrace_enabled = enabled;
    > > +#endif
    > > +}
    > > +
    > > #ifdef CONFIG_FRAME_POINTER
    > > /* TODO: need to fix this for ARM */
    > > # define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))
    >
    > I guess steven would like to see a patch which introduces both locked
    > and lockless versions and with a very good comment explaining in what
    > kind of unusual situation one can use the lockless version.

    Have sent a locked version to Steven. And, there are some comments for
    non-locked version, __ftrace_enabled_save() in above patch. What do you
    think about it?

    Best Regards,
    Huang Ying




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