RFR: 8273608: Deadlock when jcmd of OnError attaches to itself [v2]

[Xin Liu]

On Mon, 27 Sep 2021 23:27:39 GMT, Xin Liu <xliu at openjdk.org> wrote:

>> This patch allows the custom commands of OnError to attach to HotSpot itself. 
>> It sets the thread of report_and_die() to Native before os::fork_and_exec(cmd). 
>> This prevents cmds which require safepoint synchronization from deadlock.
>> eg. OnError='jcmd %p Thread.print'.
>> 
>> Without this patch, we will encounter a deadlock at safepoint synchronization. 
>> `"main" #1`  is the very thread which executes `os::fork_and_exec(cmd)`.  
>> 
>> 
>> Aborting due to java.lang.OutOfMemoryError: Java heap space
>> #
>> # A fatal error has been detected by the Java Runtime Environment:
>> #
>> #  Internal Error (debug.cpp:364), pid=94632, tid=94633
>> #  fatal error: OutOfMemory encountered: Java heap space
>> #
>> # JRE version: OpenJDK Runtime Environment (18.0) (build 18-internal+0-adhoc.xxinliu.jdk)
>> # Java VM: OpenJDK 64-Bit Server VM (18-internal+0-adhoc.xxinliu.jdk, mixed mode, tiered, compressed oops, compressed class ptrs, g1 gc, linux-amd64)
>> # No core dump will be written. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
>> #
>> # An error report file with more information is saved as:
>> # /local/home/xxinliu/JDK-2085/hs_err_pid94632.log
>> #
>> # -XX:OnError="jcmd %p Thread.print"
>> #   Executing /bin/sh -c "jcmd 94632 Thread.print" ...
>> 94632:
>> [10.616s][warning][safepoint]
>> [10.616s][warning][safepoint] # SafepointSynchronize::begin: Timeout detected:
>> [10.616s][warning][safepoint] # SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.
>> [10.616s][warning][safepoint] # SafepointSynchronize::begin: Threads which did not reach the safepoint:
>> [10.616s][warning][safepoint] # "main" #1 prio=5 os_prio=0 cpu=236.97ms elapsed=10.61s tid=0x00007f01b00232f0 nid=94633 runnable  [0x00007f01b7a08000]
>> [10.616s][warning][safepoint]    java.lang.Thread.State: RUNNABLE
>> [10.616s][warning][safepoint]
>> [10.616s][warning][safepoint] # SafepointSynchronize::begin: (End of list)
>
> Xin Liu has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
> 
>  - Add a new testcase for OutOfMemoryError thrown from NIO.
>  - Make state changer one way in VMError.
>    
>    Add a test to show that jcmd %p won't get stuck.
>  - Merge branch 'master' into JDK-8273608
>  - 8273608: Deadlock when jcmd of OnError attaches to itself
>    
>    Allow custom command of OnError to attach to HotSpot itself. This patch sets
>    the thread of report_and_die() to Native before os::fork_and_exec(cmd). This
>    prevents cmds which require safepoint synchronization from deadlock.
>    eg. OnError='jcmd %p Thread.print'.

hi, Reviewers, 

I added a dedicated test `TestOutOfMemoryErrorFromNIO.java`. TestOnError is too special. `ErrorHandlerTest` crashes HotSpot right after JNI_Create_JVM before Attach Listener Thread.  As a result, it can't trigger the deadlock. 

In TestOutOfMemoryErrorFromNIO.java, I insert 2 jcmd %p dcmds which require safepoint synchronization before and after echo. jcmd %p VM.info doesn't require safepoint. It is trivial for OnError. 

If this 'transition_into_native' works, I would like to use it in JfrEmergencyDump::on_vm_shutdown as a follow-up issue. Could you take a look at this revision?

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PR: https://git.openjdk.java.net/jdk/pull/5590