[PATCH 4/4] selftests: kvm: fix get_run_delay() ignoring fscanf() return warn

From: Shuah Khan <skhan@linuxfoundation.org>
To: pbonzini@redhat.com, shuah@kernel.org
Cc: Shuah Khan <skhan@linuxfoundation.org>,
	kvm@vger.kernel.org, linux-kselftest@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 4/4] selftests: kvm: fix get_run_delay() ignoring fscanf() return warn
Date: Wed, 15 Sep 2021 15:28:09 -0600	[thread overview]
Message-ID: <b93a1779df180a61e765bb67be7a83600585901c.1631737524.git.skhan@linuxfoundation.org> (raw)
In-Reply-To: <cover.1631737524.git.skhan@linuxfoundation.org>

Fix get_run_delay() to check fscanf() return value to get rid of the
following warning. When fscanf() fails return MIN_RUN_DELAY_NS from
get_run_delay(). Move MIN_RUN_DELAY_NS from steal_time.c to test_util.h
so get_run_delay() and steal_time.c can use it.

lib/test_util.c: In function ‘get_run_delay’:
lib/test_util.c:316:2: warning: ignoring return value of ‘fscanf’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
  316 |  fscanf(fp, "%ld %ld ", &val[0], &val[1]);
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
---
 tools/testing/selftests/kvm/include/test_util.h | 2 ++
 tools/testing/selftests/kvm/lib/test_util.c     | 4 +++-
 tools/testing/selftests/kvm/steal_time.c        | 1 -
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index c7409b9b4e5b..451fed5ce8e7 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -95,6 +95,8 @@ struct vm_mem_backing_src_alias {
 	uint32_t flag;
 };
 
+#define MIN_RUN_DELAY_NS	200000UL
+
 bool thp_configured(void);
 size_t get_trans_hugepagesz(void);
 size_t get_def_hugetlb_pagesz(void);
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index f80dd38a38b2..a9107bfae402 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -313,7 +313,9 @@ long get_run_delay(void)
 
 	sprintf(path, "/proc/%ld/schedstat", syscall(SYS_gettid));
 	fp = fopen(path, "r");
-	fscanf(fp, "%ld %ld ", &val[0], &val[1]);
+	/* Return MIN_RUN_DELAY_NS upon failure just to be safe */
+	if (fscanf(fp, "%ld %ld ", &val[0], &val[1]) < 2)
+		val[1] = MIN_RUN_DELAY_NS;
 	fclose(fp);
 
 	return val[1];
diff --git a/tools/testing/selftests/kvm/steal_time.c b/tools/testing/selftests/kvm/steal_time.c
index 51fe95a5c36a..2172d65b85e4 100644
--- a/tools/testing/selftests/kvm/steal_time.c
+++ b/tools/testing/selftests/kvm/steal_time.c
@@ -19,7 +19,6 @@
 
 #define NR_VCPUS		4
 #define ST_GPA_BASE		(1 << 30)
-#define MIN_RUN_DELAY_NS	200000UL
 
 static void *st_gva[NR_VCPUS];
 static uint64_t guest_stolen_time[NR_VCPUS];
-- 
2.30.2

