Hi Sharath,
Ah, I see: it is the call to System.exit() that is causing readLine to return.
That makes sense, and I now understand the fix.
Reviewed.
Thanks,
/Staffan
> On 28 apr. 2016, at 10:25, Sharath Ballal <sharath.bal...@oracle.com> wrote:
>
> Hi Staffan,
> The root cause of this problem is that BufferedReader.readLine() is
> intermittently returning 'null' during System.exit(0).
>
> In TTY.java:751 we are always blocking on readLine(). Whenever a user enters
> a command in JDB, the readLine() returns the command, which gets executed.
> This is running in the 'main' thread.
>
> When JDB is done, as part of the shutdown it calls System.exit() at
> Env.java:92 in a different thread 'event-handler'.
>
> Usually (in the passing cases) calling System.exit() is the end of the
> process and readLine() doesn't return 'null', but in the failing case
> readLine() at TTY.java:751 returns 'null'. This causes the string "Input
> stream closed." to be printed. The jtreg testcase looks for this string to
> decide that the testcase failed.
>
> The fix I have done is avoiding the print because we know that we are
> shutting down and hence can discard the ‘null’ returned by readLine().
>
> Regarding the testing, I have run few of the failing jtreg testcases about
> 200 times and not seen the problem (earlier I was able to recreate without
> the fix). I have to do other tests, but sent for review to do it in parallel.
>
> jdk/src/jdk.jdi/share/classes/com/sun/tools/example/debug/tty/TTY.java
>
> 708 BufferedReader in =
> 709 new BufferedReader(new InputStreamReader(System.in));
> .......
> .......
> 748 // Process interactive commands.
> 749 MessageOutput.printPrompt();
> 750 while (true) {
> 751 String ln = in.readLine();
> 752 if (ln == null) {
> 753 MessageOutput.println("Input stream closed.");
> 754 ln = "quit";
> 755 }
>
> jdk/src/jdk.jdi/share/classes/com/sun/tools/example/debug/tty/Env.java
>
> 79 static void shutdown(String message) {
> 80 if (connection != null) {
> 81 try {
> 82 connection.disposeVM();
> 83 } catch (VMDisconnectedException e) {
> 84 // Shutting down after the VM has gone away. This is
> 85 // not an error, and we just ignore it.
> 86 }
> 87 }
> 88 if (message != null) {
> 89 MessageOutput.lnprint(message);
> 90 MessageOutput.println();
> 91 }
> 92 System.exit(0);
> 93 }
>
>
> -Sharath Ballal
>
>
> From: Staffan Larsen
> Sent: Thursday, April 28, 2016 1:17 PM
> To: Sharath Ballal
> Cc: serviceability-dev@openjdk.java.net
> Subject: Re: RFR: JDK-8154144 Tests in com/sun/jdi fails intermittently with
> "jdb input stream closed prematurely
>
> Hi Sharath,
>
> Can you explain more how this help with the problem in the bug?
>
> It looks like you are trying to avoid a race by not printing the "Input
> stream closed.” message while shutting down. You added this:
> 136 ((TTY)notifier).setShuttingDown(true);
> 137 Env.shutdown(shutdownMessageKey);
> The call on line 137 will result in a System.exit(0) call if I am reading the
> code right. So adding the shutdown flag to line 136 will maybe make the race
> smaller, but isn’t really solving it?
>
> What kind of testing have you run this fix through?
>
> Thanks,
> /Staffan
>
>
>
> On 28 apr. 2016, at 09:22, Sharath Ballal <sharath.bal...@oracle.com
> <mailto:sharath.bal...@oracle.com>> wrote:
>
> Hi,
>
> Pls review the change for bug
>
> JDK-8154144 <https://bugs.openjdk.java.net/browse/JDK-8154144> - Tests in
> com/sun/jdi fails intermittently with "jdb input stream closed prematurely
>
> Webrev:
> http://cr.openjdk.java.net/~sballal/8154144/webrev.00/
> <http://cr.openjdk.java.net/~sballal/8154144/webrev.00/>
>
> -Sharath Ballal
