On Mon, 25 Jan 2021 04:46:52 GMT, David Holmes <dhol...@openjdk.org> wrote:
>> We are now confident that we have build-time and runtime support for >> clock_gettime and CLOCK_MONOTONIC on all our OpenJDK supported POSIX >> platforms - see bug report for some more details on different OS. >> Consequently we can simplify a lot of the code in this area and move common >> code to os_posix. >> >> As of glibc 2.17 the necessary functions are in glibc rather than librt, but >> we (Oracle at least) aren't yet in position to set our minimum Linux version >> to support that. We still have supported platforms at glibc 2.12. So to >> address that we link librt at build time on Linux. This seems to work find >> for older and more modern Linuxes and also works for the Apline Linux with >> Musl variant. >> >> The changes are in layered commits: >> >> Step 1: Remove build time checks. SUPPORTS_CLOCK_MONOTONIC is assumed true >> and removed. >> Step 2: make supports_monotonic_clock always true and so remove checking in >> OS code >> Step 3: Replace gettimeofday by clock_gettime(CLOCK_REALTIME) >> Step 4: Move shared time functions to os_posix.cpp >> Step 5: Alway link librt on Linux so we don't rely on glibc > 2.17 >> >> Testing: tiers 1-3 for functional testing >> built and checked (-Xlog:os) on Linux with glibc 2.12 and 2.17, >> macOS 10.13.6 and 10.15.7 > > David Holmes has updated the pull request with a new target base due to a > merge or a rebase. The pull request now contains 12 commits: > > - 'Merge branch 'master' into 8246112-mono > - Update copyrights > - Remove the always true os::supports_monotonic_clock() > - Merge > - Merge branch 'master' into 8246112-mono > - Restrict librt linking to JVM - per Magnus's request > - Merge branch 'master' into 8246112-mono > - Alway link librt on Linux so we don't rely on glibc > 2.12 > - Step 4: Move shared time functions to os_posix.cpp > - Step 3: Replace gettimeofday by clock_gettime(CLOCK_REALTIME) > - ... and 2 more: > https://git.openjdk.java.net/jdk/compare/764111ff...f4bf2b8a src/hotspot/os/posix/os_posix.cpp line 1292: > 1290: return jlong(ts.tv_sec) * MILLIUNITS + > 1291: jlong(ts.tv_nsec) / NANOUNITS_PER_MILLIUNIT; > 1292: } David, Great to see simplifications like this happening in OpenJdk code. - Posix letting you delete platform specific code. - Always nice to see 'if' branching eliminated to simplify test coverage and runtime. ------------- PR: https://git.openjdk.java.net/jdk/pull/2090
