jstack and the target output

Piotr Bzdyl piotr at bzdyl.net
Thu Nov 21 05:30:17 PST 2013

Both (java and jstack) are started using the same user. It happens on some
systems and if it happens it does with all java versions I checked (java 7
& java 8). On systems where ptrace_scope is available it is set to 0.

Best regards,

On Thu, Nov 21, 2013 at 2:14 PM, Alan Bateman <Alan.Bateman at oracle.com>wrote:

> On 21/11/2013 13:06, Piotr Bzdyl wrote:
>> Hello,
>> I wasn't sure which OpenJDK mailing list I should choose for my question.
>> As I have issues with jstack SA related group seemed the best place.
>> I have the following issue:
>> On console one (let's call it pts/1) I start a sample java app (let's say
>> its pid is 1234). On another console (pts/2) I execute:
>> jstack 1234
>> As a result pts/2 displays:
>> 1234: Unable to open socket file: target process not responding or
>> HotSpot VM not loaded
>> The -F option can be used when the target process is not responding
>> And on pts/1 I see the thread dump printed. I would rather expect that
>> the thread dump will be displayed on pts/2 and nothing will be printed to
>> pts/1. I tried to use different versions of OpenJDK but the result was
>> always the same.
>> Could you provide me any hints what might be wrong?
>> Best regards,
>> Piotr
> Are pts/1 and pts/2 the same user? Alternatively, any special options to
> the target VM that disables the attach mechanism?
> In any case, I suspect the reason that pts/1 is print the stack trace is
> that the mechanism to start the attach mechanism in the target VM requires
> signalling the target VM with SIGQUIT, the same signal that is used to get
> a VM to do a thread dump to its own stdout.
> -Alan
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