+/* GNU/Linux libthread_db support.
+
+ libthread_db is a library, provided along with libpthread.so, which
+ exposes the internals of the thread library to a debugger. It
+ allows GDB to find existing threads, new threads as they are
+ created, thread IDs (usually, the result of pthread_self), and
+ thread-local variables.
+
+ The libthread_db interface originates on Solaris, where it is
+ both more powerful and more complicated. This implementation
+ only works for LinuxThreads and NPTL, the two glibc threading
+ libraries. It assumes that each thread is permanently assigned
+ to a single light-weight process (LWP).
+
+ libthread_db-specific information is stored in the "private" field
+ of struct thread_info. When the field is NULL we do not yet have
+ information about the new thread; this could be temporary (created,
+ but the thread library's data structures do not reflect it yet)
+ or permanent (created using clone instead of pthread_create).
+
+ Process IDs managed by linux-thread-db.c match those used by
+ linux-nat.c: a common PID for all processes, an LWP ID for each
+ thread, and no TID. We save the TID in private. Keeping it out
+ of the ptid_t prevents thread IDs changing when libpthread is
+ loaded or unloaded. */
+