Messages in this thread | | | Subject | Re: [PATCH] Use bool for boolean flag in printk_once() | From | Joe Perches <> | Date | Thu, 13 Aug 2009 14:33:47 -0700 |
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On Thu, 2009-08-13 at 14:21 -0700, Andrew Morton wrote: > On Thu, 13 Aug 2009 13:48:26 -0700 > Roland Dreier <rdreier@cisco.com> wrote: > > > Using the type bool (instead of int) for the __print_once flag in the > > printk_once() macro matches the intent of the code better, and allows > > the compiler to generate smaller code; eg a typical callsite with gcc > > 4.3.3 on i386: > > > > add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-6 (-6) > > function old new delta > > static.__print_once 4 1 -3 > > get_cpu_vendor 146 143 -3 > > > > Saving 6 bytes of object size per callsite by slightly improving the > > readability of the source seems like a win to me. > > > > Signed-off-by: Roland Dreier <rolandd@cisco.com> > > --- > > include/linux/kernel.h | 4 ++-- > > 1 files changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/include/linux/kernel.h b/include/linux/kernel.h > > index d6320a3..f828ce9 100644 > > --- a/include/linux/kernel.h > > +++ b/include/linux/kernel.h > > @@ -249,10 +249,10 @@ extern bool printk_timed_ratelimit(unsigned long *caller_jiffies, > > * Print a one-time message (analogous to WARN_ONCE() et al): > > */ > > #define printk_once(x...) ({ \ > > - static int __print_once = 1; \ > > + static bool __print_once = true; \ > > \ > > if (__print_once) { \ > > - __print_once = 0; \ > > + __print_once = false; \ > > printk(x); \ > > } \ > > }) > > hm, OK, in trace_recursive_lock() we get: > > cmpl $0, __print_once.28104(%rip) #, __print_once > je .L719 #, > > changed to > > cmpb $0, __print_once.28104(%rip) # __print_once > je .L719 #,
The test should be inverted so that it's not initialized.
I submitted this once: http://lkml.indiana.edu/hypermail/linux/kernel/0905.2/02636.html
static bool printed; if (!printed) { printed = true; printk... }
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