linux-kernel - Re: perf_events: zero time running and enabled, but non-zero count

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Date:	Mon, 02 Nov 2009 16:27:16 -0800
From:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>, paulus@....ibm.com,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: perf_events: zero time running and enabled, but non-zero count

Frederic Weisbecker wrote:
> On Sun, Oct 25, 2009 at 07:37:09PM -0700, Corey Ashford wrote:
>>  I'm getting this error on a Power5 box:
>>
>> ../../lib/find_next_bit.c: In function ‘ext2_swabp’:
>> ../../lib/find_next_bit.c:168: warning: passing argument 1 of  
>> ‘__swab64p’ from incompatible pointer type
>> make: *** [util/find_next_bit.o] Error 1
>>
>> I looked at the code and it looks ok to me.  There's a cast from an  
>> "unsigned long *" to a "unsigned long long *", but those types should be  
>> of the same size (in -m64 mode), so I don't know why this is failing.
> 
> 
> Yeah, it's ok because we have the BITS_PER_LONG check. But gcc is not
> aware of that and just consider the cast as breaking the strict aliasing
> rules.
> 
> Can you tell me if the following patch works for you? (only for
> this build error).

Thanks for looking into the build problem, Frederic.  With your patch, I'm still 
seeing the error:

% patch -p1 < ~/patch
patching file tools/perf/Makefile
Hunk #1 succeeded at 845 (offset -1 lines).
% cd tools/perf
~/linux.trees.git/tools/perf
% make
Makefile:472: No libdwarf.h found or old libdwarf.h found, disables dwarf 
support. Please install libdwarf-dev/libdwarf-devel >= 20081231
     CC util/find_next_bit.o
cc1: warnings being treated as errors
../../lib/find_next_bit.c: In function 'ext2_swabp':
../../lib/find_next_bit.c:168: warning: passing argument 1 of '__swab64p' from 
incompatible pointer type
make: *** [util/find_next_bit.o] Error 1
elm3c4.beaverton.ibm.com:corey-13% cat ~/patch
diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 800783d..167bc04 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -846,8 +846,9 @@ util/bitmap.o: ../../lib/bitmap.c PERF-CFLAGS
  util/hweight.o: ../../lib/hweight.c PERF-CFLAGS
         $(QUIET_CC)$(CC) -o util/hweight.o -c $(ALL_CFLAGS) 
-DETC_PERFCONFIG='"$(ETC_PERFCONFIG_SQ)"' $<

+KFNB_FLAGS = `echo $(ALL_CFLAGS) | sed s/-Wstrict-aliasing=3//`
  util/find_next_bit.o: ../../lib/find_next_bit.c PERF-CFLAGS
-       $(QUIET_CC)$(CC) -o util/find_next_bit.o -c $(ALL_CFLAGS) 
-DETC_PERFCONFIG='"$(ETC_PERFCONFIG_SQ)"' $<
+       $(QUIET_CC)$(CC) -o util/find_next_bit.o -c $(KFNB_FLAGS) 
-DETC_PERFCONFIG='"$(ETC_PERFCONFIG_SQ)"' $<

  perf-%$X: %.o $(PERFLIBS)
         $(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) 
$(LIBS)

> 
> 
> diff --git a/tools/perf/Makefile b/tools/perf/Makefile
> index 800783d..167bc04 100644
> --- a/tools/perf/Makefile
> +++ b/tools/perf/Makefile
> @@ -846,8 +846,9 @@ util/bitmap.o: ../../lib/bitmap.c PERF-CFLAGS
>  util/hweight.o: ../../lib/hweight.c PERF-CFLAGS
>  	$(QUIET_CC)$(CC) -o util/hweight.o -c $(ALL_CFLAGS) -DETC_PERFCONFIG='"$(ETC_PERFCONFIG_SQ)"' $<
> 
> +KFNB_FLAGS = `echo $(ALL_CFLAGS) | sed s/-Wstrict-aliasing=3//`
>  util/find_next_bit.o: ../../lib/find_next_bit.c PERF-CFLAGS
> -	$(QUIET_CC)$(CC) -o util/find_next_bit.o -c $(ALL_CFLAGS) -DETC_PERFCONFIG='"$(ETC_PERFCONFIG_SQ)"' $<
> +	$(QUIET_CC)$(CC) -o util/find_next_bit.o -c $(KFNB_FLAGS) -DETC_PERFCONFIG='"$(ETC_PERFCONFIG_SQ)"' $<
> 
>  perf-%$X: %.o $(PERFLIBS)
>  	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(ALL_LDFLAGS) $(filter %.o,$^) $(LIBS)
> 
> 

-- 
Regards,

- Corey

Corey Ashford
Software Engineer
IBM Linux Technology Center, Linux Toolchain
Beaverton, OR
503-578-3507
cjashfor@...ibm.com

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