tools build feature: Check if eventfd() is available

2018-11-22T01:25:44Z

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 Cc: Andrew Morton Cc: David Ahern Cc: Davidlohr Bueso Cc: Jason Baron Cc: Jiri Olsa Cc: Namhyung Kim Cc: Wang Nan Link: https://lkml.kernel.org/n/tip-wkeldwob7dpx6jvtuzl8164k@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

linux/tools/build/feature/test-eventfd.c, branch master

tools build feature: Check if eventfd() is available