RFR: 8273608: Deadlock when jcmd of OnError attaches to itself [v4]

[David Holmes]

On Mon, 4 Oct 2021 06:39:31 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 incrementally with one additional commit since the last revision:
> 
>   Cleanup: remove a statment of debugging.

Hi Xin,

A couple of minor nits below but otherwise this seems okay now.

Thanks,
David

src/hotspot/share/runtime/mutexLocker.cpp line 376:

> 374: }
> 375: 
> 376: void unlock_locks_on_error(JavaThread* thread) {

Nit: s/thread/current/ as we must be applying this to the current thread.

src/hotspot/share/runtime/mutexLocker.hpp line 176:

> 174: void print_owned_locks_on_error(outputStream* st);
> 175: // Unlock all Mutex/Monitors currently owned by a JavaThread.
> 176: void unlock_locks_on_error(JavaThread* t);

Nit: s/t/current/ as we must be applying this to the current thread.

Also as a matter of style the parameter names in the declaration should match those in the definition.

test/hotspot/jtreg/runtime/ErrorHandling/TestOutOfMemoryErrorFromNIO.java line 26:

> 24: /*
> 25:  * @test TestOutOfMemoryErrorFromNIO
> 26:  * @bug 8155004 8273608

This shouldn't reference 8155004 as it makes no sense to claim to be a regression test for an issue that did not generate a code change.

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

Marked as reviewed by dholmes (Reviewer).

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