linux-kernel - Re: [PATCH] perf tools: Add file-handle feature test

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Message-ID: <20200402183715.GF8736@kernel.org>
Date:   Thu, 2 Apr 2020 15:37:15 -0300
From:   Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
To:     Namhyung Kim <namhyung@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Jiri Olsa <jolsa@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf tools: Add file-handle feature test

Em Thu, Apr 02, 2020 at 12:37:48PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Thu, Apr 02, 2020 at 10:52:49AM +0900, Namhyung Kim escreveu:
> > The file handle (FHANDLE) support is configurable so some systems might
> > not have it.  So add a config feature item to check it on build time
> > and reject cgroup tracking based on that.
> 
> Ok, I'll break this patch in two, add the feature test first, then fold
> the usage of HAVE_FILE_HANDLE with the patch that uses it, so that we
> keep the codebase bisectable,

> > +++ b/tools/build/feature/test-file-handle.c
> > @@ -0,0 +1,14 @@
> > +#define _GNU_SOURCE
> > +#include <sys/types.h>
> > +#include <sys/stat.h>
> > +#include <fcntl.h>
> > +
> > +int main(void)
> > +{
> > +	struct file_handle fh;
> > +	int mount_id;
> > +
> > +	name_to_handle_at(AT_FDCWD, "/", &fh, &mount_id, 0);
> > +	return 0;

Also had to do it just like you use in your patches, see patch below, to
cover this case as well:

  CC       /tmp/build/perf/util/synthetic-events.o
  CC       /tmp/build/perf/util/data.o
  CC       /tmp/build/perf/util/tsc.o
  CC       /tmp/build/perf/util/cloexec.o
util/synthetic-events.c:428:22: error: field 'fh' with   CC       /tmp/build/perf/util/call-path.o
variable sized type 'struct file_handle' not at the end of a struct or class is a GNU
      extension [-Werror,-Wgnu-variable-sized-type-not-at-end]
                struct file_handle fh;
                                   ^
1 error generated.
mv: can't rename '/tmp/build/perf/util/.synthetic-events.o.tmp': No such file or directory
make[4]: *** [/git/linux/tools/build/Makefile.build:97: /tmp/build/perf/util/synthetic-events.o] Error 1
make[4]: *** Waiting for unfinished jobs....


This is on Alpine Linux 3.11 onwards, musl libc.

- Arnaldo


diff --git a/tools/build/feature/test-file-handle.c b/tools/build/feature/test-file-handle.c
index e325b2a060ed..bed871e3978d 100644
--- a/tools/build/feature/test-file-handle.c
+++ b/tools/build/feature/test-file-handle.c
@@ -5,9 +5,12 @@
 
 int main(void)
 {
-	struct file_handle fh;
+        struct {
+                struct file_handle fh;
+                uint64_t cgroup_id;
+        } handle;
 	int mount_id;
 
-	name_to_handle_at(AT_FDCWD, "/", &fh, &mount_id, 0);
+	name_to_handle_at(AT_FDCWD, "/", &handle.fh, &mount_id, 0);
 	return 0;
 }