linux-kernel - Re: [PATCH 3/9] tools: convert comm_str.refcnt from atomic_t to refcount

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Date:   Wed, 22 Feb 2017 17:33:50 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Elena Reshetova <elena.reshetova@...el.com>
Cc:     linux-kernel@...r.kernel.org, alsa-devel@...a-project.org,
        peterz@...radead.org, gregkh@...uxfoundation.org, mingo@...hat.com,
        alexander.shishkin@...ux.intel.com, jolsa@...nel.org,
        mark.rutland@....com, akpm@...ux-foundation.org,
        matija.glavinic-pecotic.ext@...ia.com,
        Hans Liljestrand <ishkamiel@...il.com>,
        Kees Cook <keescook@...omium.org>,
        David Windsor <dwindsor@...il.com>
Subject: Re: [PATCH 3/9] tools: convert comm_str.refcnt from atomic_t to
 refcount_t

Em Tue, Feb 21, 2017 at 05:34:57PM +0200, Elena Reshetova escreveu:
> refcount_t type and corresponding API should be
> used instead of atomic_t when the variable is used as
> a reference counter. This allows to avoid accidental
> refcounter overflows that might lead to use-after-free
> situations.
> 
> Signed-off-by: Elena Reshetova <elena.reshetova@...el.com>
> Signed-off-by: Hans Liljestrand <ishkamiel@...il.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> Signed-off-by: David Windsor <dwindsor@...il.com>

You are doing two things (well three) things here:

1. converting to refcnt.h

2. Initiationg the refcount to 1, which makes this take place:

[acme@...et linux]$ m
make: Entering directory '/home/acme/git/linux/tools/perf'
  BUILD:   Doing 'make -j4' parallel build
Warning: arch/x86/include/asm/cpufeatures.h differs from kernel
  CC       /tmp/build/perf/util/comm.o
  INSTALL  trace_plugins
util/comm.c:16:25: error: ‘comm_str__get’ defined but not used [-Werror=unused-function]
 static struct comm_str *comm_str__get(struct comm_str *cs)
                         ^~~~~~~~~~~~~
cc1: all warnings being treated as errors
mv: cannot stat '/tmp/build/perf/util/.comm.o.tmp': No such file or directory
/home/acme/git/linux/tools/build/Makefile.build:101: recipe for target '/tmp/build/perf/util/comm.o' failed
make[4]: *** [/tmp/build/perf/util/comm.o] Error 1
/home/acme/git/linux/tools/build/Makefile.build:144: recipe for target 'util' failed
make[3]: *** [util] Error 2
Makefile.perf:523: recipe for target '/tmp/build/perf/libperf-in.o' failed
make[2]: *** [/tmp/build/perf/libperf-in.o] Error 2
Makefile.perf:204: recipe for target 'sub-make' failed
make[1]: *** [sub-make] Error 2
Makefile:108: recipe for target 'install-bin' failed
make: *** [install-bin] Error 2
make: Leaving directory '/home/acme/git/linux/tools/perf'
[acme@...et linux]$

3) not test building your patches :-\

I'll let this pass this time, minor, I am removing the now unused
comm_str__get() function.

- Arnaldo