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.

2 files changed, 28 insertions, 6 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);
     }
 
diff --git a/hurd/hurdsig.c b/hurd/hurdsig.c
index 72c582f00b..486be7ca9d 100644
--- a/hurd/hurdsig.c
+++ b/hurd/hurdsig.c
@@ -105,6 +105,8 @@ _hurd_thread_sigstate (thread_t thread)
 	}
       else
 	{
+	  error_t err;
+
 	  /* Use the global actions as a default for new threads.  */
 	  struct hurd_sigstate *s = _hurd_global_sigstate;
 	  if (s)
@@ -118,6 +120,11 @@ _hurd_thread_sigstate (thread_t thread)
 
 	  ss->next = _hurd_sigstates;
 	  _hurd_sigstates = ss;
+
+	  err = __mach_port_mod_refs (__mach_task_self (), thread,
+				      MACH_PORT_RIGHT_SEND, 1);
+	  if (err)
+	    __libc_fatal ("hurd: Can't add reference on Mach thread\n");
 	}
     }
   __mutex_unlock (&_hurd_siglock);
@@ -125,8 +132,7 @@ _hurd_thread_sigstate (thread_t thread)
 }
 
 /* Destroy a sigstate structure.  Called by libpthread just before the
- * corresponding thread is terminated (the kernel thread port must remain valid
- * until this function is called.) */
+ * corresponding thread is terminated.  */
 void
 _hurd_sigstate_delete (thread_t thread)
 {
@@ -143,7 +149,12 @@ _hurd_sigstate_delete (thread_t thread)
 
   __mutex_unlock (&_hurd_siglock);
   if (ss)
-    free (ss);
+    {
+      if (ss->thread != MACH_PORT_NULL)
+	__mach_port_deallocate (__mach_task_self (), ss->thread);
+
+      free (ss);
+    }
 }
 
 /* Make SS a global receiver, with pthread signal semantics.  */