Cygwin: AF_UNIX: first cut of mqueue modifications

winsup/cygwin/fhandler.h

@@ -3149,7 +3149,8 @@ public:
   int mq_timedsend (const char *, size_t, unsigned int,
 		    const struct timespec *);
   ssize_t mq_timedrecv (char *, size_t, unsigned int *,
-			const struct timespec *);
+			const struct timespec *, uint32_t = 0);
+  void mq_unlock ();
 
   struct mq_info *mqinfo () { return &mqi; }
 

winsup/cygwin/fhandler_mqueue.cc

@@ -931,7 +931,7 @@ fhandler_mqueue::mq_timedsend (const char *ptr, size_t len, unsigned int prio,
 
 ssize_t
 fhandler_mqueue::mq_timedrecv (char *ptr, size_t maxlen, unsigned int *priop,
-			       const struct timespec *abstime)
+			       const struct timespec *abstime, uint32_t flags)
 {
   int n;
   long index;
@@ -941,6 +941,7 @@ fhandler_mqueue::mq_timedrecv (char *ptr, size_t maxlen, unsigned int *priop,
   struct mq_fattr *attr;
   struct msg_hdr *msghdr;
   bool mutex_locked = false;
+  bool keep_packet = flags & (_MQ_PEEK | _MQ_PEEK_NONBLOCK);
 
   pthread_testcancel ();
 
@@ -955,14 +956,17 @@ fhandler_mqueue::mq_timedrecv (char *ptr, size_t maxlen, unsigned int *priop,
 	  __leave;
 	}
       mutex_locked = true;
-      if (maxlen < (size_t) attr->mq_msgsize)
+
+      /* Check if maxlen is too small.  When called from _mq_recv, that's ok,
+	 but for actual user space message queues, that's an error condition. */
+      if (maxlen < (size_t) attr->mq_msgsize && !(flags & _MQ_ALLOW_PARTIAL))
 	{
 	  set_errno (EMSGSIZE);
 	  __leave;
 	}
       if (attr->mq_curmsgs == 0)	/* queue is empty */
 	{
-	  if (is_nonblocking ())
+	  if (is_nonblocking () || (flags & _MQ_PEEK_NONBLOCK))
 	    {
 	      set_errno (EAGAIN);
 	      __leave;
@@ -986,24 +990,37 @@ fhandler_mqueue::mq_timedrecv (char *ptr, size_t maxlen, unsigned int *priop,
 	api_fatal ("mq_receive: curmsgs = %ld; head = 0", attr->mq_curmsgs);
 
       msghdr = (struct msg_hdr *) &mptr[index];
-      mqhdr->mqh_head = msghdr->msg_next;     /* new head of list */
-      len = msghdr->msg_len;
-      memcpy(ptr, msghdr + 1, len);           /* copy the message itself */
+
+      /* Partial read? */
+      if (maxlen < msghdr->msg_len)
+	len = maxlen;
+      else
+	len = msghdr->msg_len;
+      memcpy(ptr, msghdr + 1, len);		/* copy the message itself */
       if (priop != NULL)
 	*priop = msghdr->msg_prio;
 
-      /* Just-read message goes to front of free list */
-      msghdr->msg_next = mqhdr->mqh_free;
-      mqhdr->mqh_free = index;
-
-      /* Wake up anyone blocked in mq_send waiting for room */
-      if (attr->mq_curmsgs == attr->mq_maxmsg)
-	cond_signal (mqinfo ()->mqi_waitsend);
-      attr->mq_curmsgs--;
+      if (!keep_packet)
+	{
+	  mqhdr->mqh_head = msghdr->msg_next;     /* new head of list */
+	  /* Just-read message goes to front of free list */
+	  msghdr->msg_next = mqhdr->mqh_free;
+	  mqhdr->mqh_free = index;
+	  /* Wake up anyone blocked in mq_send waiting for room */
+	  if (attr->mq_curmsgs == attr->mq_maxmsg)
+	    cond_signal (mqinfo ()->mqi_waitsend);
+	  attr->mq_curmsgs--;
+	}
     }
   __except (EBADF) {}
   __endtry
-  if (mutex_locked)
+  if (mutex_locked && !(flags & _MQ_HOLD_LOCK))
     mutex_unlock (mqinfo ()->mqi_lock);
   return len;
 }
+
+void
+fhandler_mqueue::mq_unlock ()
+{
+  mutex_unlock (mqinfo ()->mqi_lock);
+}

winsup/cygwin/include/mqueue.h

@@ -10,6 +10,7 @@
 #include <sys/types.h>
 #include <sys/signal.h>
 #include <sys/cdefs.h>
+#include <cygwin/bits.h>
 
 #ifndef _MQUEUE_H
 #define _MQUEUE_H
@@ -38,6 +39,25 @@ int     mq_timedsend (mqd_t, const char *, size_t, unsigned int,
 		      const struct timespec *);
 int     mq_unlink (const char *name);
 
+#ifdef __INSIDE_CYGWIN__
+enum
+{
+  _MQ_ALLOW_PARTIAL	= _BIT ( 0), /* allow partial reads */
+  _MQ_PEEK	        = _BIT ( 1), /* Peek into the packet, return data,
+					but don't touch the packet at all
+					(MSG_PEEK) */
+  _MQ_PEEK_NONBLOCK     = _BIT ( 2), /* Peek into the packet, return data,
+					but don't touch the packet at all,
+					and don't block (grab_admin_pkt) */
+  _MQ_HOLD_LOCK         = _BIT ( 3), /* Don't unlock mutex after reading. */
+};
+
+ssize_t _mq_recv (mqd_t, char *, size_t, int);
+ssize_t _mq_timedrecv (mqd_t, char *, size_t, const struct timespec *, int);
+ssize_t _mq_peek (mqd_t, char *, size_t, bool);
+int     _mq_unlock (mqd_t);
+#endif
+
 __END_DECLS
 
 #endif /* _MQUEUE_H */

winsup/cygwin/mqueue_types.h

@@ -46,7 +46,7 @@ struct mq_hdr
 struct msg_hdr
 {
   int32_t         msg_next;	 /* index of next on linked list */
-  int32_t         msg_len;	 /* actual length */
+  uint32_t        msg_len;	 /* actual length */
   unsigned int    msg_prio;	 /* priority */
 };
 #pragma pack (pop)

winsup/cygwin/posix_ipc.cc

@@ -303,6 +303,68 @@ mq_receive (mqd_t mqd, char *ptr, size_t maxlen, unsigned int *priop)
   return mq_timedreceive (mqd, ptr, maxlen, priop, NULL);
 }
 
+/* Internal function to allow reading partial message packets.
+   Used from AF_UNIX code. */
+extern "C" ssize_t
+_mq_recv (mqd_t mqd, char *ptr, size_t maxlen, int flags)
+{
+  return _mq_timedrecv (mqd, ptr, maxlen, NULL, flags);
+}
+
+/* Internal function to allow reading partial message packets with timeout.
+   Used from AF_UNIX code. */
+extern "C" ssize_t
+_mq_timedrecv (mqd_t mqd, char *ptr, size_t maxlen,
+	       const struct timespec *abstime, int flags)
+{
+  int ret = -1;
+
+  cygheap_fdget fd ((int) mqd, true);
+  fhandler_mqueue *fh = fd->is_mqueue ();
+  if (!fh)
+    set_errno (EBADF);
+  else
+    ret = fh->mq_timedrecv (ptr, maxlen, NULL, abstime,
+			    _MQ_ALLOW_PARTIAL | flags);
+  return ret;
+}
+
+/* Internal function to allow peeking into message packets.
+   Used from AF_UNIX code. */
+extern "C" ssize_t
+_mq_peek (mqd_t mqd, char *ptr, size_t maxlen, bool nonblocking)
+{
+  int ret = -1;
+  int flags = _MQ_ALLOW_PARTIAL | (nonblocking ? _MQ_PEEK_NONBLOCK : _MQ_PEEK);
+
+  cygheap_fdget fd ((int) mqd, true);
+  fhandler_mqueue *fh = fd->is_mqueue ();
+  if (!fh)
+    set_errno (EBADF);
+  else
+    ret = fh->mq_timedrecv (ptr, maxlen, NULL, NULL, flags);
+  return ret;
+}
+
+/* Internal function to unlock a queue after mq_receive was called
+   with _MQ_HOLD_LOCK.  Used from AF_UNIX code. */
+extern "C" int
+_mq_unlock (mqd_t mqd)
+{
+  int ret = -1;
+
+  cygheap_fdget fd ((int) mqd, true);
+  fhandler_mqueue *fh = fd->is_mqueue ();
+  if (!fh)
+    set_errno (EBADF);
+  else
+    {
+      fh->mq_unlock ();
+      ret = 0;
+    }
+  return ret;
+}
+
 extern "C" int
 mq_close (mqd_t mqd)
 {