From 2170017a1cd033b6f28e16476921022712a522d8 Mon Sep 17 00:00:00 2001 From: Wan-Teh Chang Date: Wed, 7 Dec 2016 16:16:02 -0800 Subject: avutil: fix data race in av_get_cpu_flags() Make the one-time initialization in av_get_cpu_flags() thread-safe. The static variables |flags|, |cpuflags_mask|, and |checked| in libavutil/cpu.c are read and written using normal load and store operations. These are considered as data races. The fix is to use atomic load and store operations. Remove the |checked| variable because the invalid value of -1 for |flags| can be used to indicate the same condition. Rename |flags| to |cpu_flags| and move it to file scope. The fix can be verified by running the libavutil/tests/cpu_init.c test program under ThreadSanitizer: ./configure --toolchain=clang-tsan make libavutil/tests/cpu_init libavutil/tests/cpu_init There should be no warnings from ThreadSanitizer. Co-author: Dmitry Vyukov of Google, who suggested the data race fix. Signed-off-by: Wan-Teh Chang --- libavutil/cpu.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'libavutil/cpu.h') diff --git a/libavutil/cpu.h b/libavutil/cpu.h index deff4ccf55..c205ee16f6 100644 --- a/libavutil/cpu.h +++ b/libavutil/cpu.h @@ -73,8 +73,6 @@ int av_get_cpu_flags(void); /** * Set a mask on flags returned by av_get_cpu_flags(). * This function is mainly useful for testing. - * - * @warning this function is not thread safe. */ void av_set_cpu_flags_mask(int mask); -- cgit v1.2.3