[tip:perf/core] perf tools: Do parameter validation earlier on fetch_kernel_version()

[tip-bot for Arnaldo Carvalho de Melo <tipbot@zytor.com>]

Commit-ID:  44b58e06e8e3872b6741e5aee59a7a93dfe3834a
Gitweb:     http://git.kernel.org/tip/44b58e06e8e3872b6741e5aee59a7a93dfe3834a
Author:     Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Tue, 20 Jun 2017 12:19:16 -0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Tue, 20 Jun 2017 12:19:16 -0300

perf tools: Do parameter validation earlier on fetch_kernel_version()

While trying to reduce util.[ch] I noticed that fetch_kernel_version()
and fetch_ubuntu_kernel_version() do lots of operations only to check if
they are needed, i.e. it checks if the pointer where to return the
kernel version is NULL only after obtaining the kernel version from
/proc/version_signature or by parsing the results from uname().

Do it earlier not to confuse people reading this code in the future :-)

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-i94qwyekk4tzbu0b9ce1r1mz@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/util.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 3cd4299..988111e 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -350,8 +350,12 @@ fetch_ubuntu_kernel_version(unsigned int *puint)
 	size_t line_len = 0;
 	char *ptr, *line = NULL;
 	int version, patchlevel, sublevel, err;
-	FILE *vsig = fopen("/proc/version_signature", "r");
+	FILE *vsig;
 
+	if (!puint)
+		return 0;
+
+	vsig = fopen("/proc/version_signature", "r");
 	if (!vsig) {
 		pr_debug("Open /proc/version_signature failed: %s\n",
 			 strerror(errno));
@@ -381,8 +385,7 @@ fetch_ubuntu_kernel_version(unsigned int *puint)
 		goto errout;
 	}
 
-	if (puint)
-		*puint = (version << 16) + (patchlevel << 8) + sublevel;
+	*puint = (version << 16) + (patchlevel << 8) + sublevel;
 	err = 0;
 errout:
 	free(line);
@@ -409,6 +412,9 @@ fetch_kernel_version(unsigned int *puint, char *str,
 		str[str_size - 1] = '\0';
 	}
 
+	if (!puint || int_ver_ready)
+		return 0;
+
 	err = sscanf(utsname.release, "%d.%d.%d",
 		     &version, &patchlevel, &sublevel);
 
@@ -418,8 +424,7 @@ fetch_kernel_version(unsigned int *puint, char *str,
 		return -1;
 	}
 
-	if (puint && !int_ver_ready)
-		*puint = (version << 16) + (patchlevel << 8) + sublevel;
+	*puint = (version << 16) + (patchlevel << 8) + sublevel;
 	return 0;
 }