POSIX: detach every thread, not just the main pid - #244
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Process::detach() only issued PTRACE_DETACH for _pid, the main thread. ptrace() traces each thread of a multithreaded process as its own tracee: threads created after the initial attach arrive via PTRACE_EVENT_CLONE rather than a fresh PTRACE_ATTACH, but each one still needs its own PTRACE_DETACH. Detaching only the main pid leaves every other thread parked in its last ptrace-stop indefinitely, so a detached multithreaded inferior can appear to hang rather than resume. This reproduces directly in lldb's TestDetachResumes: a program spawns five threads that all hit a breakpoint at once, the debugger detaches, and the test waits for the process to finish running on its own. The other four threads never got continued, so the process never exits. Enumerate every tracked thread and detach the rest before the existing, error-checked detach of the main pid. When LLDB sends D1, DebugSessionImplBase::onDetach suspends every thread first because the target is expected to remain stopped after detaching. PTRACE_DETACH always resumes the tracee as part of detaching regardless of any signal already pending from that earlier suspend, so the new per-thread detach calls need to carry that intent explicitly rather than rely on it as a side effect: pass SIGSTOP as the detach signal for every thread, main included, when the caller asked for the process to stay stopped, and 0 otherwise. detach() picks up a stopped parameter for this, threaded through from onDetach; the Windows override ignores it, since DebugActiveProcessStop always resumes the debuggee regardless.
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Process::detach() only issued PTRACE_DETACH for _pid, the main thread. ptrace() traces each thread of a multithreaded process as its own tracee: threads created after the initial attach arrive via PTRACE_EVENT_CLONE rather than a fresh PTRACE_ATTACH, but each one still needs its own PTRACE_DETACH. Detaching only the main pid leaves every other thread parked in its last ptrace-stop indefinitely, so a detached multithreaded inferior can appear to hang rather than resume.
This reproduces directly in lldb's TestDetachResumes: a program spawns five threads that all hit a breakpoint at once, the debugger detaches, and the test waits for the process to finish running on its own. The other four threads never got continued, so the process never exits.
Enumerate every tracked thread and best-effort detach the rest before the existing, error-checked detach of the main pid.