Matt,
I think you are probably right, although there are other places where it
directly calls SetPublicState(). I was wondering about the possibility
there could be other listeners waiting for a broadcast public Stop
event. Is that a possibility?
Some others here were investigating some unit tests that were failing
intermittently (StopHook). Their description of the problem sounds
unrelated to the launch code, but this patch also magically fixes that.
Shawn.
On 8/6/2014 6:26 AM, Matthew Gardiner wrote:
Shawn,
Like I said earlier your patch worked. However I think the right fix
is to arrange that ShouldBroadcast returns false for this first stop.
I believe this, because firstly no stops should be reported here since
the user is only interested in launching a program, and additionally
because it enables us to fix lldb without removing the call to
HandlePrivateEvent. This, I think, is important to preserve as the
central point for process state change handling.
Matt
Shawn Best wrote:
Hi Matthew,
I have also been tracking this bug. I believe there are other bugs
in the unit tests failing indirectly because of this. I also have a
patch that will fix it, but was sitting on it until the other one
landed. These bugs do not show up on OSX since the inferiors are
launched separately then attached to.
The first odd thing the launching code does is push an IOHandler when
it sees the state transition to 'launching'. This is odd because I
believe the launching program will always come up in a stopped state
which will immediately pop the IOHandler.
At launch, the process comes up in the stopped state. The launch
code manually calls HandlePrivateEvent() with the stop event, which
then broadcasts the Event. When HandleProcessEvent gets the public
stop, it dumps out the current thread state just as if an executing
inferior hit a breakpoint and stopped.
One way to fix this would be:
1. Don't push io handler when state is 'launching'
2. Instead of manually calling HandlePrivateEvent, call
SetPublicState().
Alternately, we could try and debug why ShouldBroadcast() returns
true, but that appears to be by design since it is expecting the
public stop event to pop the IOHandler that had been pushed when
launching.
I have attached a patch demonstrating this. In conjunction with the
other patch for IOHandler race condition, it will fix a bunch of this
kind of behaviour.
Shawn.
On 8/5/2014 6:59 AM, Matthew Gardiner wrote:
Jim,
I've been trying to debug an issue (I see it on 64-bit linux) where,
I do "target create" and "process launch" and despite not requesting
*stop at entry*, the first stop (which I believe is just the initial
ptrace attach stop) is reported to the lldb command line. I added
some fprintf to Process::HandlePrivateEvent, which counts the number
of eStoppedState events seen and whether ShouldBroadcastEvent
returns true for this event. Here's the output from my program with
diagnostic:
(lldb) target create ~/me/i64-hello.elf
Current executable set to '~/me/i64-hello.elf' (x86_64).
(lldb) process launch
MG Process::HandlePrivateEvent launching stopped_count 0
should_broadcast 1
Process 31393 launching
MG Process::HandlePrivateEvent stopped stopped_count 1
should_broadcast 1
MG Process::HandlePrivateEvent running stopped_count 1
should_broadcast 1
Process 31393 launched: 'i64-hello.elf' (x86_64)
Process 31393 stopped
* thread #1: tid = 31393, 0x0000003675a011f0, name =
'i64-hello.elf', stop reason = trace
frame #0: 0x0000003675a011f0
-> 0x3675a011f0: movq %rsp, %rdi
0x3675a011f3: callq 0x3675a046e0
0x3675a011f8: movq %rax, %r12
0x3675a011fb: movl 0x21eb97(%rip), %eax
(lldb) MG Process::HandlePrivateEvent stopped stopped_count 2
should_broadcast 0
MG Process::HandlePrivateEvent running stopped_count 2
should_broadcast 0
MG Process::HandlePrivateEvent stopped stopped_count 3
should_broadcast 0
MG Process::HandlePrivateEvent running stopped_count 3
should_broadcast 0
In summary, lldb reports the inferior to be stopped (even though
/proc/pid/status and lldb "target list" say it is running). Clearly
this is wrong (hence my earlier post).
Am I correct in assuming that when ShouldBroadcastEvent returns
true this means that lldb should show this event to the debug user?
(And thus hide other events where ShouldBroadcastEvent=false).
What puzzled me was why ShouldBroadcastEvent return true for this
very first stop. Is this a bug?
I also spent sometime at ShouldBroadcastEvent and saw that this:
case eStateStopped:
case eStateCrashed:
case eStateSuspended:
{
....
if (was_restarted || should_resume ||
m_resume_requested)
{
evaluates as false, and hence the PrivateResume code is not
called... does this seem buggy to you for this very first stop?
I thought I'd try asking you, since in a previous mail from Greg, he
cited you as being a thread-plan expert. (Hope that's ok!). I'd
really appreciate your help in clarifying the above questions for
me, and if you have time, giving me some ideas as to how to trace
this one further e.g. how m_thread_list.ShouldStop and
m_thread_list.ShouldReportStop should behave, etc.
thanks for your help
Matt
Matthew Gardiner wrote:
Folks,
In addition to the overlapping prompt race Shawn Best and myself
are looking at, I'm seeing another issue where if I launch a
process, I get a stop (presumably the in) being reported to the UI.
(lldb) target create ~/mydir/i64-hello.elf
Current executable set to '~/mydir/i64-hello.elf' (x86_64).
(lldb) process launch
Process 27238 launching
Process 27238 launched: '64-hello.elf' (x86_64)
Process 27238 stopped
* thread #1: tid = 27238, 0x0000003675a011f0, name = 'i64-hello.elf'
frame #0:
(lldb) target list
Current targets:
* target #0: i64-hello.elf ( arch=x86_64-unknown-linux,
platform=host, pid=27238, state=running )
(lldb)
As you can see the "target list" reflects that the process is
running. Which I confirmed by looking at /proc/27238/status.
Anyone else seeing this?
thanks
Matt
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