Messages in this thread | | | Subject | Re: [PATCH] ratelimit: check the condition in WARN_RATELIMIT first | From | Joe Perches <> | Date | Fri, 17 Aug 2012 11:45:39 -0700 |
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On Fri, 2012-08-17 at 20:15 +0200, Jiri Slaby wrote: > On 08/17/2012 07:39 PM, Joe Perches wrote: > > On Fri, 2012-08-17 at 15:42 +0200, Jiri Slaby wrote: > >> Before calling __ratelimit in __WARN_RATELIMIT, check the condition > >> first. When this check was not there, we got constant income of: > >> tty_init_dev: 60 callbacks suppressed > >> tty_init_dev: 59 callbacks suppressed > > [] > >> diff --git a/include/linux/ratelimit.h b/include/linux/ratelimit.h > > [] > >> @@ -49,8 +49,9 @@ extern int ___ratelimit(struct ratelimit_state *rs, const char *func); > >> #define __WARN_RATELIMIT(condition, state, format...) \ > >> ({ \ > >> int rtn = 0; \ > >> - if (unlikely(__ratelimit(state))) \ > >> - rtn = WARN(condition, format); \ > >> + int __rtcond = !!condition; \ > >> + if (unlikely(__rtcond && __ratelimit(state))) \ > >> + rtn = WARN(__rtcond, format); \ > >> rtn; \ > >> }) > >> > > > > Hi Jiri. > > > > This seems fine to me but are there any conditions that > > are computationally expensive? > > It's not about expensiveness of the computation. The complexity remained > the same except I moved the computation one layer up.
If ratelimit(state) is not true, condition wasn't tested or performed at all. With this change, it's always done.
> > Maybe something like this? [] > Yup, something like that looks OK to me.
OK, David, do you want an official patch?
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