RFR: 8368565: Adjust comment regarding dependency of libjvm.so to librt

[Matthias Baesken]

On Thu, 25 Sep 2025 03:16:49 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> We have a legacy dependency of libjvm to librt for the` clock_*` functions :
>> https://github.com/openjdk/jdk/blob/f993f90c86f89eb0c7f42ebecb45a68eae0bd9ea/make/autoconf/libraries.m4#L139
>> 
>> But this is for very old systems with distros like RHEL 6 or SLES11 with glibc 2.16 or older, where the clock_ functions were still in librt ; but those ancient distros play no role any more for current JDK26.
>> On the other hand, we now use the `timer_*` functions from librt e.g. in JFR and these are _really_  in librt so the comment should be adjusted.
>
> make/autoconf/libraries.m4 line 141:
> 
>> 139:   # librt
>> 140:   if test "x$OPENJDK_TARGET_OS" = xlinux; then
>> 141:     # Needed for the timer_* functions from librt used in JFR
> 
> It isn't just JFR - CompilerThreadTimeout also uses timers. I suggest just one comment at line 139 "#librt - for timers".

Additional to JFR I see some stuff in ASSERT coding in the compiler threads coding using  `timer_*` so it is not important for release JVMs.  But probably you are right we can simplify the comments, no need to mention old stuff and too many details.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/27473#discussion_r2378062934