Hi Chris,
It attaches to the instrumentation buffer when it is getting a MonitoredVm
object inside check() method at
jdk.jcmd/share/classes/sun/tools/common/ProcessArgumentMatcher.java:85. It
needs a monitored VM to retrieve a main class name ( line 86) and use it on
lines 100 and 104 to filter out processes that don't match.
private static boolean check(VirtualMachineDescriptor vmd, String excludeClass,
String partialMatch) {
81 String mainClass = null;
82 try {
83 VmIdentifier vmId = new VmIdentifier(vmd.id());
84 MonitoredHost monitoredHost =
MonitoredHost.getMonitoredHost(vmId);
85 MonitoredVm monitoredVm =
monitoredHost.getMonitoredVm(vmId, -1);
86 mainClass = MonitoredVmUtil.mainClass(monitoredVm, true);
87 monitoredHost.detach(monitoredVm);
88 } catch (NullPointerException npe) {
89 // There is a potential race, where a running java app is
being
90 // queried, unfortunately the java app has shutdown after
this
91 // method is started but before getMonitoredVM is called.
92 // If this is the case, then the /tmp/hsperfdata_xxx/pid
file
93 // will have disappeared and we will get a
NullPointerException.
94 // Handle this gracefully....
95 return false;
96 } catch (MonitorException | URISyntaxException e) {
97 return false;
98 }
99
100 if (excludeClass != null && mainClass.equals(excludeClass)) {
101 return false;
102 }
103
104 if (partialMatch != null && mainClass.indexOf(partialMatch) ==
-1) {
105 return false;
106 }
107
108 return true;
109 }
Below is the stack trace for that:
attach:-1, Perf (jdk.internal.perf)
attachImpl:270, Perf (jdk.internal.perf)
attach:200, Perf (jdk.internal.perf)
<init>:64, PerfDataBuffer (sun.jvmstat.perfdata.monitor.protocol.local)
<init>:68, LocalMonitoredVm (sun.jvmstat.perfdata.monitor.protocol.local)
getMonitoredVm:77, MonitoredHostProvider
(sun.jvmstat.perfdata.monitor.protocol.local)
check:85, ProcessArgumentMatcher (sun.tools.common)
getVMDs:129, ProcessArgumentMatcher (sun.tools.common)
getVirtualMachinePids:154, ProcessArgumentMatcher (sun.tools.common)
main:83, JCmd (sun.tools.jcmd)
Best regards,
Daniil
On 11/29/18, 5:16 PM, "Chris Plummer" <[email protected]> wrote:
Can you remind me why the test is trying to attach to all running java
processes.
Chris
On 11/29/18 1:30 PM, Daniil Titov wrote:
> Thank you, David!
>
> The proposed fix didn't help. It still hangs at some occasions.
Additional tracing showed that when jcmd is invoked with the main class name it
iterates over all running Java processes and temporary attaches to them to
retrieve the main class name. It hangs while trying to attach to one of the
running Java processes. There are numerous Java processes running at the host
machine some associated with the test framework itself and another with the
tests running in parallel. It is not clear what exact is this particular
process since the jcmd hangs before retrieving the process' main class name,
but after all tests terminated the process with this id is no longer running.
I have to revoke this review since more investigation is required.
>
>
> Best regards,
> Daniil
>
>
>
> On 11/11/18, 1:35 PM, "David Holmes" <[email protected]> wrote:
>
> Hi Daniil,
>
> I took a quick look at this one ... two minor comments
>
> The static class names could just be "Process" as they will acquire
the
> enclosing class name as part of their own name anyway. As it is this
> gets repeated eg:
>
> HelpTest$HelpTestProcess
> InvalidCommandTest$InvalidCommandTestProcess
>
> TestJavaProcess.java:
>
> 39 public static void main(String argv[]) {
>
> Nit: Should be "String[] argv" in Java style
>
> Thanks,
> David
>
> On 10/11/2018 3:18 PM, Daniil Titov wrote:
> > Please review the change that fixes
serviceability/dcmd/framework/* tests from a time out. The fix for JDK-8166642
made serviceability/dcmd/framework/* tests non-concurrent to ensure that they
don't interact with each other and there are no multiple tests running
simultaneously since all they do share the common main class name
com.sun.javatest.regtest.agent.MainWrapper. However, it looks like the tests
from other directories still might run in parallel with these tests and they
also have com.sun.javatest.regtest.agent.MainWrapper as a main class.
> >
> > The fix ensures that each serviceability/dcmd/framework/* test
uses a Java process with a unique main class name when connecting to this
process with jcmd and the main class name.
> >
> > Bug: https://bugs.openjdk.java.net/browse/JDK-8205654
> > Webrev: http://cr.openjdk.java.net/~dtitov/8205654/webrev.001/
> >
> > Best regards,
> > Daniil
> >
> >
>
>
>
