From: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> commit 11c6cbe706f218a8dc7e1f962f12b3a52ddd33a9 upstream. A new 'perf bench epoll' will use this, and to disable it for older systems, add a feature test for this API. This is just a simple program that if successfully compiled, means that the feature is present, at least at the library level, in a build that sets the output directory to /tmp/build/perf (using O=/tmp/build/perf), we end up with: $ ls -la /tmp/build/perf/feature/test-eventfd* -rwxrwxr-x. 1 acme acme 8176 Nov 21 15:58 /tmp/build/perf/feature/test-eventfd.bin -rw-rw-r--. 1 acme acme 588 Nov 21 15:58 /tmp/build/perf/feature/test-eventfd.d -rw-rw-r--. 1 acme acme 0 Nov 21 15:58 /tmp/build/perf/feature/test-eventfd.make.output $ ldd /tmp/build/perf/feature/test-eventfd.bin linux-vdso.so.1 (0x00007fff3bf3f000) libc.so.6 => /lib64/libc.so.6 (0x00007fa984061000) /lib64/ld-linux-x86-64.so.2 (0x00007fa984417000) $ grep eventfd -A 2 -B 2 /tmp/build/perf/FEATURE-DUMP feature-dwarf=1 feature-dwarf_getlocations=1 feature-eventfd=1 feature-fortify-source=1 feature-sync-compare-and-swap=1 $ The main thing here is that in the end we'll have -DHAVE_EVENTFD in CFLAGS, and then the 'perf bench' entry needing that API can be selectively pruned. Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: David Ahern <dsahern@xxxxxxxxx> Cc: Davidlohr Bueso <dbueso@xxxxxxx> Cc: Jason Baron <jbaron@xxxxxxxxxx> Cc: Jiri Olsa <jolsa@xxxxxxxxxx> Cc: Namhyung Kim <namhyung@xxxxxxxxxx> Cc: Wang Nan <wangnan0@xxxxxxxxxx> Link: https://lkml.kernel.org/n/tip-wkeldwob7dpx6jvtuzl8164k@xxxxxxxxxxxxxx Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> Cc: Guenter Roeck <linux@xxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- tools/build/Makefile.feature | 1 + tools/build/feature/Makefile | 4 ++++ tools/build/feature/test-all.c | 5 +++++ tools/build/feature/test-eventfd.c | 9 +++++++++ tools/perf/Makefile.config | 5 ++++- 5 files changed, 23 insertions(+), 1 deletion(-) create mode 100644 tools/build/feature/test-eventfd.c --- a/tools/build/Makefile.feature +++ b/tools/build/Makefile.feature @@ -31,6 +31,7 @@ FEATURE_TESTS_BASIC := backtrace \ dwarf \ dwarf_getlocations \ + eventfd \ fortify-source \ sync-compare-and-swap \ get_current_dir_name \ --- a/tools/build/feature/Makefile +++ b/tools/build/feature/Makefile @@ -5,6 +5,7 @@ FILES= test-bionic.bin \ test-dwarf.bin \ test-dwarf_getlocations.bin \ + test-eventfd.bin \ test-fortify-source.bin \ test-sync-compare-and-swap.bin \ test-get_current_dir_name.bin \ @@ -90,6 +91,9 @@ $(OUTPUT)test-bionic.bin: $(OUTPUT)test-libelf.bin: $(BUILD) -lelf +$(OUTPUT)test-eventfd.bin: + $(BUILD) + $(OUTPUT)test-get_current_dir_name.bin: $(BUILD) --- a/tools/build/feature/test-all.c +++ b/tools/build/feature/test-all.c @@ -50,6 +50,10 @@ # include "test-dwarf_getlocations.c" #undef main +#define main main_test_eventfd +# include "test-eventfd.c" +#undef main + #define main main_test_libelf_getphdrnum # include "test-libelf-getphdrnum.c" #undef main @@ -174,6 +178,7 @@ int main(int argc, char *argv[]) main_test_glibc(); main_test_dwarf(); main_test_dwarf_getlocations(); + main_test_eventfd(); main_test_libelf_getphdrnum(); main_test_libelf_gelf_getnote(); main_test_libelf_getshdrstrndx(); --- /dev/null +++ b/tools/build/feature/test-eventfd.c @@ -0,0 +1,9 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2018, Red Hat Inc, Arnaldo Carvalho de Melo <acme@xxxxxxxxxx> + +#include <sys/eventfd.h> + +int main(void) +{ + return eventfd(0, EFD_NONBLOCK); +} --- a/tools/perf/Makefile.config +++ b/tools/perf/Makefile.config @@ -281,11 +281,14 @@ ifndef NO_BIONIC endif endif +ifeq ($(feature-eventfd), 1) + CFLAGS += -DHAVE_EVENTFD +endif + ifeq ($(feature-get_current_dir_name), 1) CFLAGS += -DHAVE_GET_CURRENT_DIR_NAME endif - ifdef NO_LIBELF NO_DWARF := 1 NO_DEMANGLE := 1
