Hurd: make sigstates hold a reference on thread ports

This change is required in order to correctly release per-thread
resources. Directly reusing the threading library reference isn't
possible since the sigstate is also used early in the main thread,
before threading is initialized.

* hurd/hurd/signal.h (_hurd_self_sigstate): Drop thread reference after
calling _hurd_thread_sigstate.
(_hurd_critical_section_lock): Likewise.
* hurd/hurdsig.c (_hurd_thread_sigstate): Add a reference on the thread.
(_hurd_sigstate_delete): Drop thread reference.

1 files changed, 14 insertions, 3 deletions

diff --git a/hurd/hurd/signal.h b/hurd/hurd/signal.h
index db60e6f0a1..1d1218a88a 100644
--- a/hurd/hurd/signal.h
+++ b/hurd/hurd/signal.h
@@ -64,7 +64,9 @@ struct hurd_sigstate
 
     spin_lock_t lock;		/* Locks most of the rest of the structure.  */
 
+    /* The signal state holds a reference on the thread port.  */
     thread_t thread;
+
     struct hurd_sigstate *next; /* Linked-list of thread sigstates.  */
 
     sigset_t blocked;		/* What signals are blocked.  */
@@ -118,7 +120,9 @@ extern struct hurd_sigstate *_hurd_sigstates;
 
 extern struct mutex _hurd_siglock; /* Locks _hurd_sigstates.  */
 
-/* Get the sigstate of a given thread, taking its lock.  */
+/* Get the sigstate of a given thread.  If there was no sigstate for
+   the thread, one is created, and the thread gains a reference.  If
+   the given thread is MACH_PORT_NULL, return the global sigstate.  */
 
 extern struct hurd_sigstate *_hurd_thread_sigstate (thread_t);
 
@@ -161,7 +165,11 @@ _hurd_self_sigstate (void)
   struct hurd_sigstate **location =
     (void *) __hurd_threadvar_location (_HURD_THREADVAR_SIGSTATE);
   if (*location == NULL)
-    *location = _hurd_thread_sigstate (__mach_thread_self ());
+    {
+      thread_t self = __mach_thread_self ();
+      *location = _hurd_thread_sigstate (self);
+      __mach_port_deallocate (__mach_task_self (), self);
+    }
   return *location;
 }
 
@@ -192,11 +200,14 @@ _hurd_critical_section_lock (void)
   struct hurd_sigstate *ss = *location;
   if (ss == NULL)
     {
+      thread_t self = __mach_thread_self ();
+
       /* The thread variable is unset; this must be the first time we've
 	 asked for it.  In this case, the critical section flag cannot
 	 possible already be set.  Look up our sigstate structure the slow
 	 way; this locks the sigstate lock.  */
-      ss = *location = _hurd_thread_sigstate (__mach_thread_self ());
+      ss = *location = _hurd_thread_sigstate (self);
+      __mach_port_deallocate (__mach_task_self (), self);
       __spin_unlock (&ss->lock);
     }