On Fri, 15 Jan 2021 04:57:24 GMT, David Holmes <[email protected]> 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 Looks like a good cleanup. But please minimize the use of -lrt to hotspot only as per the comment above. make/autoconf/flags-ldflags.m4 line 116: > 114: # has glibc 2.17, this can be removed as the functions are > 115: # in libc. > 116: OS_LDFLAGS="-lrt" I believe this should be `OS_LDFLAGS_JVM_ONLY`, right? ------------- Changes requested by ihse (Reviewer). PR: https://git.openjdk.java.net/jdk/pull/2090
