xnu-3247.1.106.tar.gz

[apple/xnu.git] / osfmk / kern / ipc_sync.c

diff --git a/osfmk/kern/ipc_sync.c b/osfmk/kern/ipc_sync.c
index 3e960b1d9abf7cdd77d4f75f27c75da517f4fbe1..fdc418c1dac168c731706147d633dbe84a49bf82 100644 (file)
--- a/osfmk/kern/ipc_sync.c
+++ b/osfmk/kern/ipc_sync.c
@@ -37,18 +37,26 @@
 #include <ipc/port.h>
 #include <ipc/ipc_space.h>
 #include <ipc/ipc_port.h>
+#include <mach/mach_types.h>
 #include <mach/semaphore.h>
 #include <mach/lock_set_server.h>
 #include <mach/mach_port_server.h>
 #include <mach/port.h>
 
 
+/*
+ *     Routine:        port_name_to_semaphore
+ *     Purpose:
+ *             Convert from a port name in the current space to a semaphore.
+ *             Produces a semaphore ref, which may be null.
+ *     Conditions:
+ *             Nothing locked.
+ */
 kern_return_t
 port_name_to_semaphore(
        mach_port_name_t        name,
        semaphore_t             *semaphorep)
 {
-       semaphore_t semaphore;
        ipc_port_t kern_port;
        kern_return_t kr;
 
@@ -56,7 +64,7 @@ port_name_to_semaphore(
                *semaphorep = SEMAPHORE_NULL;
                return KERN_INVALID_NAME;
        }
-       
+
        kr = ipc_object_translate(current_space(), name, MACH_PORT_RIGHT_SEND,
                                  (ipc_object_t *) &kern_port);
        if (kr != KERN_SUCCESS) {
@@ -66,51 +74,127 @@ port_name_to_semaphore(
        /* have the port locked */
        assert(IP_VALID(kern_port));
 
-       if (!ip_active(kern_port) || (ip_kotype(kern_port) != IKOT_SEMAPHORE)) {
-               ip_unlock(kern_port);
-               *semaphorep = SEMAPHORE_NULL;
-               return KERN_INVALID_ARGUMENT;
-       }
-
-       semaphore = (semaphore_t) kern_port->ip_kobject;
-       assert(semaphore != SEMAPHORE_NULL);
-       semaphore_reference(semaphore);
+       *semaphorep = convert_port_to_semaphore(kern_port);
        ip_unlock(kern_port);
 
-       *semaphorep = semaphore;
        return KERN_SUCCESS;
 }
-       
+
+/*
+ *     Routine:        convert_port_to_semaphore
+ *     Purpose:
+ *             Convert from a port to a semaphore.
+ *             Doesn't consume the port [send-right] ref;
+ *             produces a semaphore ref, which may be null.
+ *     Conditions:
+ *             Caller has a send-right reference to port.
+ *             Port may or may not be locked.
+ */
 semaphore_t
 convert_port_to_semaphore (ipc_port_t port)
 {
-       semaphore_t semaphore = SEMAPHORE_NULL;
 
-       if (IP_VALID (port)) {
-               ip_lock(port);
-               if (ip_active(port) && (ip_kotype(port) == IKOT_SEMAPHORE)) {
+       if (IP_VALID(port)) {
+               semaphore_t semaphore;
+
+               /*
+                * No need to lock because we have a reference on the
+                * port, and if it is a true semaphore port, that reference
+                * keeps the semaphore bound to the port (and active).
+                */
+               if (ip_kotype(port) == IKOT_SEMAPHORE) {
+                       assert(ip_active(port));
                        semaphore = (semaphore_t) port->ip_kobject;
                        semaphore_reference(semaphore);
+                       return (semaphore);
                }
-               ip_unlock(port);
        }
-
-       return (semaphore);
+       return SEMAPHORE_NULL;
 }
 
 
+/*
+ *     Routine:        convert_semaphore_to_port
+ *     Purpose:
+ *             Convert a semaphore reference to a send right to a
+ *             semaphore port.
+ *
+ *             Consumes the semaphore reference.  If the semaphore
+ *             port currently has no send rights (or doesn't exist
+ *             yet), the reference is donated to the port to represent
+ *             all extant send rights collectively.
+ */
 ipc_port_t
 convert_semaphore_to_port (semaphore_t semaphore)
 {
-       ipc_port_t port;
+       ipc_port_t port, send;
 
        if (semaphore == SEMAPHORE_NULL)
                return (IP_NULL);
 
        /* caller is donating a reference */
-       port = ipc_port_make_send(semaphore->port);
+       port = semaphore->port;
+
+       if (!IP_VALID(port)) {
+               port = ipc_port_alloc_kernel();
+               assert(IP_VALID(port));
+               ipc_kobject_set_atomically(port, (ipc_kobject_t) semaphore, IKOT_SEMAPHORE);
+
+               /* If we lose the race, deallocate and pick up the other guy's port */
+               if (!OSCompareAndSwapPtr(IP_NULL, port, &semaphore->port)) {
+                       ipc_port_dealloc_kernel(port);
+                       port = semaphore->port;
+                       assert(ip_kotype(port) == IKOT_SEMAPHORE);
+                       assert(port->ip_kobject == (ipc_kobject_t)semaphore);
+               }
+       }
+
+       ip_lock(port);
+       assert(ip_active(port));
+       send = ipc_port_make_send_locked(port);
+
+       if (1 == port->ip_srights) {
+               ipc_port_t old_notify;
+
+               /* transfer our ref to the port, and arm the no-senders notification */
+               assert(IP_NULL == port->ip_nsrequest);
+               ipc_port_nsrequest(port, port->ip_mscount, ipc_port_make_sonce_locked(port), &old_notify);
+               /* port unlocked */
+               assert(IP_NULL == old_notify);
+       } else {
+               /* piggyback on the existing port reference, so consume ours */
+               ip_unlock(port);
+               semaphore_dereference(semaphore);
+       }
+       return (send);
+}
+
+/*
+ * Routine:    semaphore_notify
+ * Purpose:
+ *     Called whenever the Mach port system detects no-senders
+ *     on the semaphore port.
+ *
+ *     When a send-right is first created, a no-senders
+ *     notification is armed (and a semaphore reference is donated).
+ *
+ *     A no-senders notification will be posted when no one else holds a
+ *     send-right (reference) to the semaphore's port. This notification function
+ *     will consume the semaphore reference donated to the extant collection of
+ *     send-rights.
+ */
+void
+semaphore_notify(mach_msg_header_t *msg)
+{
+       mach_no_senders_notification_t *notification = (void *)msg;
+       ipc_port_t port = notification->not_header.msgh_remote_port;
+       semaphore_t semaphore;
+
+       assert(ip_active(port));
+       assert(IKOT_SEMAPHORE == ip_kotype(port));
+       semaphore = (semaphore_t)port->ip_kobject;
+
        semaphore_dereference(semaphore);
-       return (port);
 }
 
 lock_set_t