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Fix handling of non-waitable zombie threads. Now they are not

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considered running, so WaitStop doesn't lock up and
breakpoints get installed and uninstalled.  We also don't try
to detach from them, since that will fail.

R=rsc
APPROVED=rsc
DELTA=35  (26 added, 2 deleted, 7 changed)
OCL=31683
CL=31731
This commit is contained in:
Austin Clements 2009-07-16 09:48:37 -07:00
parent 13960ae8ae
commit 1902283053
2 changed files with 33 additions and 9 deletions
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3
usr/austin/ptrace/ptrace-nptl.txt
View File

@ -115,7 +115,8 @@ don't think the process is done until all of the threads have exited.
Unfortunately, signals cannot be delivered to non-waitable zombies.
Most notably, SIGSTOP cannot be delivered; as a result, when you
broadcast SIGSTOP to all of the threads, you must not wait for
non-waitable zombies to stop.
non-waitable zombies to stop. Furthermore, any ptrace command on a
non-waitable zombie, including PTRACE_DETACH, will return ESRCH.
== Multi-threaded debuggers ==

39
usr/austin/ptrace/ptrace_linux.go
View File

@ -43,7 +43,21 @@ const (
*/
// Each thread can be in one of the following set of states.
// Each state satisfies (isRunning() || isStopped() || isTerminal()).
// Each state satisfies
// isRunning() || isStopped() || isZombie() || isTerminal().
//
// Running threads can be sent signals and must be waited on, but they
// cannot be inspected using ptrace.
//
// Stopped threads can be inspected and continued, but cannot be
// meaningfully waited on. They can be sent signals, but the signals
// will be queued until they are running again.
//
// Zombie threads cannot be inspected, continued, or sent signals (and
// therefore they cannot be stopped), but they must be waited on.
//
// Terminal threads no longer exist in the OS and thus you can't do
// anything with them.
type threadState string;
const (
@ -61,13 +75,17 @@ const (
)
func (ts threadState) isRunning() bool {
return ts == running || ts == singleStepping || ts == stopping || ts == exiting;
return ts == running || ts == singleStepping || ts == stopping;
}
func (ts threadState) isStopped() bool {
return ts == stopped || ts == stoppedBreakpoint || ts == stoppedSignal || ts == stoppedThreadCreate || ts == stoppedExiting;
}
func (ts threadState) isZombie() bool {
return ts == exiting;
}
func (ts threadState) isTerminal() bool {
return ts == exited || ts == detached;
}
@ -429,7 +447,7 @@ func (t *thread) setState(new threadState) {
t.state = new;
t.logTrace("state %v -> %v", old, new);
if !old.isRunning() && new.isRunning() {
if !old.isRunning() && (new.isRunning() || new.isZombie()) {
// Start waiting on this thread
go t.wait();
}
@ -1020,7 +1038,11 @@ func (p *process) Continue() os.Error {
if err != nil {
return err;
}
t.setState(running);
if t.state == stoppedExiting {
t.setState(exiting);
} else {
t.setState(running);
}
}
return nil;
});
@ -1050,8 +1072,6 @@ func (p *process) WaitStop() os.Error {
h := &transitionHandler{};
h.handle = func (st *thread, old, new threadState) {
if !new.isRunning() {
// TODO(austin) This gets stuck on
// zombie threads.
if p.someRunningThread() == nil {
ready <- nil;
return;
@ -1094,8 +1114,11 @@ func (p *process) Detach() os.Error {
}
for pid, t := range p.threads {
if err := t.ptraceDetach(); err != nil {
return err;
if t.state.isStopped() {
// We can't detach from zombies.
if err := t.ptraceDetach(); err != nil {
return err;
}
}
t.setState(detached);
p.threads[pid] = nil, false;