[PATCH 10/15] Hurd signals: provide a sigstate destructor

[Jeremie Koenig <jk at jk dot fr dot eu dot org>]

We can no longer afford to keep stale sigstate structures in the
_hurd_sigstates list if some of them are marked as global receivers,
otherwise we might try to use them to deliver signals.

* hurd/hurdsig.c (_hurd_sigstate_delete): New function. Remove a sigstate
from the list and release its memory. To be used by libpthread at thread
destruction time.
* hurd/Versions (_hurd_sigstate_delete): Add the new symbol.
* hurd/hurd/signal.h (_hurd_sigstate_delete): Add its prototype.
---
 hurd/Versions      |    1 +
 hurd/hurd/signal.h |    3 +++
 hurd/hurdsig.c     |   22 ++++++++++++++++++++++
 3 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/hurd/Versions b/hurd/Versions
index fe65d25..ec405db 100644
--- a/hurd/Versions
+++ b/hurd/Versions
@@ -162,6 +162,7 @@ libc {
     _hurd_sigstate_lock;
     _hurd_sigstate_pending;
     _hurd_sigstate_unlock;
+    _hurd_sigstate_delete;
   }
 
 %if !SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_2)
diff --git a/hurd/hurd/signal.h b/hurd/hurd/signal.h
index 6b4d695..1c4733a 100644
--- a/hurd/hurd/signal.h
+++ b/hurd/hurd/signal.h
@@ -150,6 +150,9 @@ extern struct sigaction *_hurd_sigstate_actions (struct hurd_sigstate *ss);
 extern sigset_t _hurd_sigstate_pending (const struct hurd_sigstate *ss);
 extern void _hurd_sigstate_unlock (struct hurd_sigstate *ss);
 
+/* Used by libpthread to remove stale sigstate structures.  */
+extern void _hurd_sigstate_delete (thread_t thread);
+
 #ifndef _HURD_SIGNAL_H_EXTERN_INLINE
 #define _HURD_SIGNAL_H_EXTERN_INLINE __extern_inline
 #endif
diff --git a/hurd/hurdsig.c b/hurd/hurdsig.c
index eaf5ac1..f5fa659 100644
--- a/hurd/hurdsig.c
+++ b/hurd/hurdsig.c
@@ -126,6 +126,28 @@ _hurd_thread_sigstate (thread_t thread)
   return ss;
 }
 
+/* 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.) */
+void
+_hurd_sigstate_delete (thread_t thread)
+{
+  struct hurd_sigstate **ssp, *ss;
+
+  __mutex_lock (&_hurd_siglock);
+  for (ssp = &_hurd_sigstates; *ssp; ssp = &(*ssp)->next)
+    if ((*ssp)->thread == thread)
+      break;
+
+  ss = *ssp;
+  if (ss)
+    *ssp = ss->next;
+
+  __mutex_unlock (&_hurd_siglock);
+  if (ss)
+    free (ss);
+}
+
 /* Make SS a global receiver, with pthread signal semantics.  */
 void
 _hurd_sigstate_set_global_rcv (struct hurd_sigstate *ss)
-- 
1.7.5.3