@@ -187,6 +187,7 @@ TESTPROGS = adler32 \
camellia \
color_utils \
cpu \
+ cpu_init \
crc \
des \
dict \
@@ -44,7 +44,20 @@
#include <unistd.h>
#endif
-static int flags, checked;
+static int cpu_flags = -1;
+
+static int get_cpu_flags(void)
+{
+ if (ARCH_AARCH64)
+ return ff_get_cpu_flags_aarch64();
+ if (ARCH_ARM)
+ return ff_get_cpu_flags_arm();
+ if (ARCH_PPC)
+ return ff_get_cpu_flags_ppc();
+ if (ARCH_X86)
+ return ff_get_cpu_flags_x86();
+ return 0;
+}
void av_force_cpu_flags(int arg){
if ( (arg & ( AV_CPU_FLAG_3DNOW |
@@ -69,33 +82,22 @@ void av_force_cpu_flags(int arg){
arg |= AV_CPU_FLAG_MMX;
}
- flags = arg;
- checked = arg != -1;
+ cpu_flags = arg;
}
int av_get_cpu_flags(void)
{
- if (checked)
- return flags;
-
- if (ARCH_AARCH64)
- flags = ff_get_cpu_flags_aarch64();
- if (ARCH_ARM)
- flags = ff_get_cpu_flags_arm();
- if (ARCH_PPC)
- flags = ff_get_cpu_flags_ppc();
- if (ARCH_X86)
- flags = ff_get_cpu_flags_x86();
-
- checked = 1;
+ int flags = cpu_flags;
+ if (flags == -1) {
+ flags = get_cpu_flags();
+ cpu_flags = flags;
+ }
return flags;
}
void av_set_cpu_flags_mask(int mask)
{
- checked = 0;
- flags = av_get_cpu_flags() & mask;
- checked = 1;
+ cpu_flags = get_cpu_flags() & mask;
}
int av_parse_cpu_flags(const char *s)
new file mode 100644
@@ -0,0 +1,72 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/*
+ * This test program tests whether the one-time initialization in
+ * av_get_cpu_flags() has data races.
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "config.h"
+
+#include "libavutil/cpu.h"
+#include "libavutil/thread.h"
+
+#if HAVE_PTHREADS
+static void *thread_main(void *arg)
+{
+ int *flags = arg;
+
+ *flags = av_get_cpu_flags();
+ return NULL;
+}
+#endif
+
+
+int main(int argc, char **argv)
+{
+#if HAVE_PTHREADS
+ int cpu_flags1;
+ int cpu_flags2;
+ int ret;
+ pthread_t thread1;
+ pthread_t thread2;
+
+ if ((ret = pthread_create(&thread1, NULL, thread_main, &cpu_flags1))) {
+ fprintf(stderr, "pthread_create failed: %s.\n", strerror(ret));
+ return 1;
+ }
+ if ((ret = pthread_create(&thread2, NULL, thread_main, &cpu_flags2))) {
+ fprintf(stderr, "pthread_create failed: %s.\n", strerror(ret));
+ return 1;
+ }
+ pthread_join(thread1, NULL);
+ pthread_join(thread2, NULL);
+
+ if (cpu_flags1 < 0)
+ return 2;
+ if (cpu_flags2 < 0)
+ return 2;
+ if (cpu_flags1 != cpu_flags2)
+ return 3;
+#endif
+
+ return 0;
+}
Remove the |checked| variable because the invalid value of -1 for |flags| can be used to indicate the same condition. Also rename |flags| to |cpu_flags| because there are a local variable and a function parameter named |flags| in the same file. Add a test program libavutil/tests/cpu_init.c to check whether the one-time initialization in av_get_cpu_flags() has data races. Co-author: Dmitry Vyukov of Google Signed-off-by: Wan-Teh Chang <wtc@google.com> --- libavutil/Makefile | 1 + libavutil/cpu.c | 40 ++++++++++++++------------ libavutil/tests/cpu_init.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 94 insertions(+), 19 deletions(-) create mode 100644 libavutil/tests/cpu_init.c