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

From: Corey Ashford
Date: Mon Nov 02 2009 - 19:27:23 EST


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 âext2_swabpâ:
../../lib/find_next_bit.c:168: warning: passing argument 1 of â__swab64pâ 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@xxxxxxxxxx

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