RFR: 8358568: C2 compilation hits "must have a monitor" assert with -XX:-GenerateSynchronizationCode [v5]

[Aleksey Shipilev]

On Fri, 4 Jul 2025 06:43:02 GMT, hanguanqiang <duke at openjdk.org> wrote:

>> This PR fixes JDK-8358568, a JVM crash triggered when running with -XX:-GenerateSynchronizationCode
>> 
>> Problem：
>> When synchronization code generation is disabled by -XX:-GenerateSynchronizationCode, the compiler’s do_monitor_exit() method still tries to access monitor objects without checking if any monitors exist.This causes an assertion failure and JVM crash.
>> 
>> Root Cause：
>> Parse::do_monitor_exit() calls shared_unlock() using monitor info unconditionally,but with GenerateSynchronizationCode disabled, no monitor info is available, leading to invalid access.
>> 
>> Fix
>> Add a check in do_monitor_exit() to skip monitor unlocking if GenerateSynchronizationCode is false, avoiding invalid monitor access and preventing the crash.
>
> hanguanqiang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   correct an error
>   
>   correct an error

I renamed the JBS bug, match the PR title, please. Also, go to https://github.com/hgqxjj/jdk/actions -- and enable the workflows. We need to have a clean GHA run before we can integrate.

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

PR Comment: https://git.openjdk.org/jdk/pull/26108#issuecomment-3035170988