Get rid of nptl/sysdeps/ entirely!

1 files changed, 245 insertions, 6 deletions

diff --git a/sysdeps/unix/sysv/linux/mq_notify.c b/sysdeps/unix/sysv/linux/mq_notify.c
index a61839f507..d50a9f2d57 100644
--- a/sysdeps/unix/sysv/linux/mq_notify.c
+++ b/sysdeps/unix/sysv/linux/mq_notify.c
@@ -1,5 +1,6 @@
 /* Copyright (C) 2004-2014 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
+   Contribute by Ulrich Drepper <drepper@redhat.com>, 2004.
 
    The GNU C Library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
@@ -15,27 +16,265 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <assert.h>
 #include <errno.h>
+#include <fcntl.h>
 #include <mqueue.h>
-#include <stddef.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
 #include <sysdep.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <not-cancel.h>
+#include <nptl/pthreadP.h>
+
 
 #ifdef __NR_mq_notify
 
+/* Defined in the kernel headers: */
+#define NOTIFY_COOKIE_LEN	32	/* Length of the cookie used.  */
+#define NOTIFY_WOKENUP		1	/* Code for notifcation.  */
+#define NOTIFY_REMOVED		2	/* Code for closed message queue
+					   of de-notifcation.  */
+
+
+/* Data structure for the queued notification requests.  */
+union notify_data
+{
+  struct
+  {
+    void (*fct) (union sigval);	/* The function to run.  */
+    union sigval param;		/* The parameter to pass.  */
+    pthread_attr_t *attr;	/* Attributes to create the thread with.  */
+    /* NB: on 64-bit machines the struct as a size of 24 bytes.  Which means
+       byte 31 can still be used for returning the status.  */
+  };
+  char raw[NOTIFY_COOKIE_LEN];
+};
+
+
+/* Keep track of the initialization.  */
+static pthread_once_t once = PTHREAD_ONCE_INIT;
+
+
+/* The netlink socket.  */
+static int netlink_socket = -1;
+
+
+/* Barrier used to make sure data passed to the new thread is not
+   resused by the parent.  */
+static pthread_barrier_t notify_barrier;
+
+
+/* Modify the signal mask.  We move this into a separate function so
+   that the stack space needed for sigset_t is not deducted from what
+   the thread can use.  */
+static int
+__attribute__ ((noinline))
+change_sigmask (int how, sigset_t *oss)
+{
+  sigset_t ss;
+  sigfillset (&ss);
+  return pthread_sigmask (how, &ss, oss);
+}
+
+
+/* The function used for the notification.  */
+static void *
+notification_function (void *arg)
+{
+  /* Copy the function and parameter so that the parent thread can go
+     on with its life.  */
+  volatile union notify_data *data = (volatile union notify_data *) arg;
+  void (*fct) (union sigval) = data->fct;
+  union sigval param = data->param;
+
+  /* Let the parent go.  */
+  (void) pthread_barrier_wait (&notify_barrier);
+
+  /* Make the thread detached.  */
+  (void) pthread_detach (pthread_self ());
+
+  /* The parent thread has all signals blocked.  This is probably a
+     bit surprising for this thread.  So we unblock all of them.  */
+  (void) change_sigmask (SIG_UNBLOCK, NULL);
+
+  /* Now run the user code.  */
+  fct (param);
+
+  /* And we are done.  */
+  return NULL;
+}
+
+
+/* Helper thread.  */
+static void *
+helper_thread (void *arg)
+{
+  while (1)
+    {
+      union notify_data data;
+
+      ssize_t n = recv (netlink_socket, &data, sizeof (data),
+			MSG_NOSIGNAL | MSG_WAITALL);
+      if (n < NOTIFY_COOKIE_LEN)
+	continue;
+
+      if (data.raw[NOTIFY_COOKIE_LEN - 1] == NOTIFY_WOKENUP)
+	{
+	  /* Just create the thread as instructed.  There is no way to
+	     report a problem with creating a thread.  */
+	  pthread_t th;
+	  if (__builtin_expect (pthread_create (&th, data.attr,
+						notification_function, &data)
+				== 0, 0))
+	    /* Since we passed a pointer to DATA to the new thread we have
+	       to wait until it is done with it.  */
+	    (void) pthread_barrier_wait (&notify_barrier);
+	}
+      else if (data.raw[NOTIFY_COOKIE_LEN - 1] == NOTIFY_REMOVED)
+	/* The only state we keep is the copy of the thread attributes.  */
+	free (data.attr);
+    }
+  return NULL;
+}
+
+
+static void
+reset_once (void)
+{
+  once = PTHREAD_ONCE_INIT;
+}
+
+
+static void
+init_mq_netlink (void)
+{
+  /* This code might be called a second time after fork().  The file
+     descriptor is inherited from the parent.  */
+  if (netlink_socket == -1)
+    {
+      /* Just a normal netlink socket, not bound.  */
+      netlink_socket = socket (AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, 0);
+      /* No need to do more if we have no socket.  */
+      if (netlink_socket == -1)
+	return;
+    }
+
+  int err = 1;
+
+  /* Initialize the barrier.  */
+  if (__builtin_expect (pthread_barrier_init (&notify_barrier, NULL, 2) == 0,
+			0))
+    {
+      /* Create the helper thread.  */
+      pthread_attr_t attr;
+      (void) pthread_attr_init (&attr);
+      (void) pthread_attr_setdetachstate (&attr, PTHREAD_CREATE_DETACHED);
+      /* We do not need much stack space, the bare minimum will be enough.  */
+      (void) pthread_attr_setstacksize (&attr, __pthread_get_minstack (&attr));
+
+      /* Temporarily block all signals so that the newly created
+	 thread inherits the mask.  */
+      sigset_t oss;
+      int have_no_oss = change_sigmask (SIG_BLOCK, &oss);
+
+      pthread_t th;
+      err = pthread_create (&th, &attr, helper_thread, NULL);
+
+      /* Reset the signal mask.  */
+      if (!have_no_oss)
+	pthread_sigmask (SIG_SETMASK, &oss, NULL);
+
+      (void) pthread_attr_destroy (&attr);
+
+      if (err == 0)
+	{
+	  static int added_atfork;
+
+	  if (added_atfork == 0
+	      && pthread_atfork (NULL, NULL, reset_once) != 0)
+	    {
+	      /* The child thread will call recv() which is a
+		 cancellation point.  */
+	      (void) pthread_cancel (th);
+	      err = 1;
+	    }
+	  else
+	    added_atfork = 1;
+	}
+    }
+
+  if (err != 0)
+    {
+      close_not_cancel_no_status (netlink_socket);
+      netlink_socket = -1;
+    }
+}
+
+
 /* Register notification upon message arrival to an empty message queue
    MQDES.  */
 int
 mq_notify (mqd_t mqdes, const struct sigevent *notification)
 {
-  /* mq_notify which handles SIGEV_THREAD is included in the thread
-     add-on.  */
-  if (notification != NULL
-      && notification->sigev_notify == SIGEV_THREAD)
+  /* Make sure the type is correctly defined.  */
+  assert (sizeof (union notify_data) == NOTIFY_COOKIE_LEN);
+
+  /* Special treatment needed for SIGEV_THREAD.  */
+  if (notification == NULL || notification->sigev_notify != SIGEV_THREAD)
+    return INLINE_SYSCALL (mq_notify, 2, mqdes, notification);
+
+  /* The kernel cannot directly start threads.  This will have to be
+     done at userlevel.  Since we cannot start threads from signal
+     handlers we have to create a dedicated thread which waits for
+     notifications for arriving messages and creates threads in
+     response.  */
+
+  /* Initialize only once.  */
+  pthread_once (&once, init_mq_netlink);
+
+  /* If we cannot create the netlink socket we cannot provide
+     SIGEV_THREAD support.  */
+  if (__glibc_unlikely (netlink_socket == -1))
     {
       __set_errno (ENOSYS);
       return -1;
     }
-  return INLINE_SYSCALL (mq_notify, 2, mqdes, notification);
+
+  /* Create the cookie.  It will hold almost all the state.  */
+  union notify_data data;
+  memset (&data, '\0', sizeof (data));
+  data.fct = notification->sigev_notify_function;
+  data.param = notification->sigev_value;
+
+  if (notification->sigev_notify_attributes != NULL)
+    {
+      /* The thread attribute has to be allocated separately.  */
+      data.attr = (pthread_attr_t *) malloc (sizeof (pthread_attr_t));
+      if (data.attr == NULL)
+	return -1;
+
+      memcpy (data.attr, notification->sigev_notify_attributes,
+	      sizeof (pthread_attr_t));
+    }
+
+  /* Construct the new request.  */
+  struct sigevent se;
+  se.sigev_notify = SIGEV_THREAD;
+  se.sigev_signo = netlink_socket;
+  se.sigev_value.sival_ptr = &data;
+
+  /* Tell the kernel.  */
+  int retval = INLINE_SYSCALL (mq_notify, 2, mqdes, &se);
+
+  /* If it failed, free the allocated memory.  */
+  if (__glibc_unlikely (retval != 0))
+    free (data.attr);
+
+  return retval;
 }
 
 #else