Name: tb29552 Date: 03/06/2001


java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.0)
Java HotSpot(TM) Client VM (build 1.3.0, mixed mode)



If a breakpoint happens immediately after "cont"
or "resume" command (e.g. if a breakpoint is set inside
a tight loop) then from time to time jdb loses track of
the current thread
these is cause by a race in jdb code
look at tty/Commands.java

    void commandCont() {
        if (ThreadInfo.current == null) {
            out.println("Nothing suspended.");
            return;
        }
        Env.vm().resume();
        ThreadInfo.invalidateAll();
    }

obviously, if a next breakpoint is hit before invalidateAll()
is finished, then invalidateAll() invalidates the breakpoint context

Same thing for commandResume()
(Review ID: 118077)
======================================================================
tim.bell@Eng 2001-05-23

Test case:

% cat Test.java
class Test {
    public int doTest(int i, int max) {
        int m = 0;
        int result = 0;
        for (int j = i; j < max; j++) {
            result += j; // Source Line 5
            m++;
            m++;
        }
        return (result);
    }
   public static void main(String[] args) {
      System.out.println("Hello World");
      Test my = new Test();
      System.out.println(my.doTest(1,1000));
   }
}

% cat jdb.ini
stop at Test:6
stop at Test:7


Easy to reproduce on a single-CPU system:


% javac -g Test.java
% jdb Test
Initializing jdb...
*** Reading commands from /tmpjava/4422139/jdb.ini
Deferring breakpoint Test:6.
It will be set after the class is loaded.
> Deferring breakpoint Test:7.
It will be set after the class is loaded.
> > run
run Test
>
VM Started: Set deferred breakpoint Test:7
Set deferred breakpoint Test:6
Hello World

Breakpoint hit: thread="main", Test.doTest(), line=6, bci=11
  6 result += j; // Source Line 5

main[1] cont

Breakpoint hit: > thread="main", Test.doTest(), line=7, bci=18
  7 m++;

> cont
Nothing suspended.
> thread 1
main[1] cont

Breakpoint hit: > thread="main", Test.doTest(), line=6, bci=11
  6 result += j; // Source Line 5

> cont
Nothing suspended.
> thread 1
main[1] cont

Breakpoint hit: > thread="main", Test.doTest(), line=7, bci=18
  7 m++;

> cont
Nothing suspended.
>