Hi Yasumasa,
Sorry about the delay in getting back to you. I've looked at your
updated webrev:
http://cr.openjdk.java.net/~ysuenaga/JDK-8225690/webrev.02/
Comments below:
On 7/10/19 5:18 PM, Yasumasa Suenaga wrote:
Hi Chris,
Thank you for your comment!
I uploaded new webrev:
http://cr.openjdk.java.net/~ysuenaga/JDK-8225690/webrev.01/
I write some comments the following.
On 2019/07/11 4:29, Chris Plummer wrote:
Hi Yasumasa,
I just took a quick look at this. I understand a little about how the
attach mechanism works, but am by no means an expert, and find myself
easily lost in some of the logic. I'll look again after others have
also contributed comments. Here area few comments.
I don't understand the need for the following in
attach_listener_thread_entry()
428 AttachListener::set_state(AL_NOT_INITIALIZED);
There is no path to this statement since the only way out of the loop
is the following:
I agree with you, but I think we need to reset the status of Attach
Listener
in the end of the function.
Why, if it is never executed?
We might be able to use ShouldNotReachHere() at here.
I think ShouldNotReachHere() would be appropriate at the end of this
function, but it's really just adding an assert for what I've already
said is the case. You can't reach this point so there is no reason to
add any logic there (other than asserting).
How are errors in AttachListener::init() properly propagated. I see
is_init_trigger() does the following:
548 if (os::Posix::matches_effective_uid_or_root(st.st_uid)) {
549 init();
550 log_trace(attach)("Attach triggered by %s", fn);
551 return true;
So "true" is returned even though init() maybe have failed, but then
check_socket_file() doesn't even check the result from
is_init_trigger():
509 is_init_trigger();
510 return true;
The SIGBREAK code does check the is_init_trigger() result, but since
init() failures are not propagated to is_init_trigger(), the result
may not be accurate.
In case of Linux, HotSpot has some phase to start Attach Listener:
1. Check attach file (.attach_pid*) -> is_init_trigger()
2. Create unix domain socket -> is_init_trigger()
3. Start Attach Listener thread -> init()
is_init_trigger() returns whether init() is kicked or not.
OTOH init() is declared as a void function, so we cannot know
Attach Listener is started.
(We can know it through exception message on the console, but
it will not handle in HotSpot.)
Thus I thought we can add new field AttachListener::_state
to know current status of Attach Listener.
Ok.
Have you done any testing of the error handling by forcing errors to
happen?
Do you mean it is the race of the attach request?
If so, I've added the testcase (ConcAttachTest.java).
If you mean the failure of init() and/or is_init_trigger(),
I do not have idea how to test it.
Yes, I mean unexpected failures that you've written code to handle. The
best way to test them is either in gdb or just programmatically
introduce the failure (change the code so the failure happens). I'm just
asking that you step through the code one time under failure, not that
you have a test to induce the failure, which probably is not possible.
The following code needs a comment to indicate that the current state
is AL_INITIALIZED, and if the socket file was removed it needs to be
recreated and a new socket opened.
379 } else if (AttachListener::check_socket_file()) {
380 continue;
381 }
I added it in new webrev.
Thanks!
Chris
Thanks,
Yasumasa
thanks,
Chris
On 7/4/19 6:27 AM, Yasumasa Suenaga wrote:
Hi all,
Please review this change:
JBS: https://bugs.openjdk.java.net/browse/JDK-8225690
webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8225690/webrev.00/
This issue has been discussed on [1] and [2].
This webrev passed tests on submit repo
(mach5-one-ysuenaga-JDK-8225690-20190704-1214-3626907).
It includes the fix for JDK-8225193. They relate each other, so I
fix them together.
Thanks,
Yasumasa
[1]
https://mail.openjdk.java.net/pipermail/serviceability-dev/2019-July/028585.html
[2]
https://mail.openjdk.java.net/pipermail/serviceability-dev/2019-June/028418.html
