# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1679791936 -3600
# Node ID 2dd97d71e6273478226e3c982ec886cd30f2d69d
# Parent  6e89c2c7fb49f65dbb790c626fa8ebc8fef65067
Removed the indicated notifier from unsubscribe operations since it cannot be
trivially compared to any subscribed notifier. Thus, only a single notifier can
be used with any given file, pipe, directory or process endpoint.

diff -r 6e89c2c7fb49 -r 2dd97d71e627 libexec/include/exec/process_monitor.h
--- a/libexec/include/exec/process_monitor.h	Sun Mar 26 01:36:53 2023 +0100
+++ b/libexec/include/exec/process_monitor.h	Sun Mar 26 01:52:16 2023 +0100
@@ -42,6 +42,10 @@
                _task = L4_INVALID_CAP, _mapped_task = L4_INVALID_CAP,
                _thread = L4_INVALID_CAP, _mapped_thread = L4_INVALID_CAP;
 
+  /* Notification support. */
+
+  l4_cap_idx_t _notifier = L4_INVALID_CAP;
+
 public:
   explicit ProcessMonitor();
 
@@ -75,7 +79,7 @@
 
   virtual long subscribe(l4_cap_idx_t notifier, notify_flags_t flags);
 
-  virtual long unsubscribe(l4_cap_idx_t notifier);
+  virtual long unsubscribe();
 };
 
 /* vim: tabstop=2 expandtab shiftwidth=2
diff -r 6e89c2c7fb49 -r 2dd97d71e627 libexec/lib/src/process_monitor.cc
--- a/libexec/lib/src/process_monitor.cc	Sun Mar 26 01:36:53 2023 +0100
+++ b/libexec/lib/src/process_monitor.cc	Sun Mar 26 01:52:16 2023 +0100
@@ -144,14 +144,24 @@
 
 long ProcessMonitor::subscribe(l4_cap_idx_t notifier, notify_flags_t flags)
 {
-  return NotificationSupport::subscribe(notifier, flags);
+  unsubscribe();
+
+  _notifier = notifier;
+  return NotificationSupport::subscribe(_notifier, flags);
 }
 
 /* Unsubscribe from notifications. */
 
-long ProcessMonitor::unsubscribe(l4_cap_idx_t notifier)
+long ProcessMonitor::unsubscribe()
 {
-  return NotificationSupport::unsubscribe(notifier);
+  if (l4_is_valid_cap(_notifier))
+  {
+    long err = NotificationSupport::unsubscribe(_notifier);
+    _notifier = L4_INVALID_CAP;
+    return err;
+  }
+  else
+    return L4_EOK;
 }
 
 /* vim: tabstop=2 expandtab shiftwidth=2
diff -r 6e89c2c7fb49 -r 2dd97d71e627 libfsserver/include/fsserver/directory_resource.h
--- a/libfsserver/include/fsserver/directory_resource.h	Sun Mar 26 01:36:53 2023 +0100
+++ b/libfsserver/include/fsserver/directory_resource.h	Sun Mar 26 01:52:16 2023 +0100
@@ -63,7 +63,7 @@
 
     virtual long subscribe(l4_cap_idx_t notifier, notify_flags_t flags);
 
-    virtual long unsubscribe(l4_cap_idx_t notifier);
+    virtual long unsubscribe();
 };
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 6e89c2c7fb49 -r 2dd97d71e627 libfsserver/include/fsserver/file_pager.h
--- a/libfsserver/include/fsserver/file_pager.h	Sun Mar 26 01:36:53 2023 +0100
+++ b/libfsserver/include/fsserver/file_pager.h	Sun Mar 26 01:52:16 2023 +0100
@@ -83,7 +83,7 @@
 
     virtual long subscribe(l4_cap_idx_t notifier, notify_flags_t flags);
 
-    virtual long unsubscribe(l4_cap_idx_t notifier);
+    virtual long unsubscribe();
 };
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 6e89c2c7fb49 -r 2dd97d71e627 libfsserver/include/fsserver/pipe_pager.h
--- a/libfsserver/include/fsserver/pipe_pager.h	Sun Mar 26 01:36:53 2023 +0100
+++ b/libfsserver/include/fsserver/pipe_pager.h	Sun Mar 26 01:52:16 2023 +0100
@@ -77,7 +77,7 @@
 
     virtual long subscribe(l4_cap_idx_t notifier, notify_flags_t flags);
 
-    virtual long unsubscribe(l4_cap_idx_t notifier);
+    virtual long unsubscribe();
 };
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 6e89c2c7fb49 -r 2dd97d71e627 libfsserver/lib/directories/directory_resource.cc
--- a/libfsserver/lib/directories/directory_resource.cc	Sun Mar 26 01:36:53 2023 +0100
+++ b/libfsserver/lib/directories/directory_resource.cc	Sun Mar 26 01:52:16 2023 +0100
@@ -52,7 +52,12 @@
    appropriate. */
 
 void DirectoryResource::close()
-{   
+{
+    /* Notify other users of the file and unsubscribe. */
+
+    _provider->notify_others(_notifier, NOTIFY_PEER_CLOSED, NOTIFY_VALUES_NULL);
+    unsubscribe();
+   
     /* Detach the resource, potentially removing the file provider. */
     
     _provider->registry()->detach(fileid, _provider);
@@ -125,15 +130,27 @@
 
 long DirectoryResource::subscribe(l4_cap_idx_t notifier, notify_flags_t flags)
 {
+    /* A single notifier is recorded so that it may be unsubscribed when the
+       directory is closed. */
+
+    unsubscribe();
+
     _notifier = notifier;
-    return _provider->subscribe(notifier, flags);
+    return _provider->subscribe(_notifier, flags);
 }
 
 /* Unsubscribe from notifications. */
 
-long DirectoryResource::unsubscribe(l4_cap_idx_t notifier)
+long DirectoryResource::unsubscribe()
 {
-    return _provider->unsubscribe(notifier);
+    if (l4_is_valid_cap(_notifier))
+    {
+        long err = _provider->unsubscribe(_notifier);
+        _notifier = L4_INVALID_CAP;
+        return err;
+    }
+    else
+        return L4_EOK;
 }
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 6e89c2c7fb49 -r 2dd97d71e627 libfsserver/lib/files/file_pager.cc
--- a/libfsserver/lib/files/file_pager.cc	Sun Mar 26 01:36:53 2023 +0100
+++ b/libfsserver/lib/files/file_pager.cc	Sun Mar 26 01:52:16 2023 +0100
@@ -53,7 +53,7 @@
     /* Notify other users of the file and unsubscribe. */
 
     _provider->notify_others(_notifier, NOTIFY_PEER_CLOSED, NOTIFY_VALUES_NULL);
-    unsubscribe(_notifier);
+    unsubscribe();
 
     /* Detach the pager, potentially removing the file provider. */
 
@@ -155,18 +155,24 @@
     /* A single notifier is recorded so that it may be unsubscribed when the
        file is closed. */
 
-    if ((notifier != _notifier) && l4_is_valid_cap(_notifier))
-        unsubscribe(_notifier);
+    unsubscribe();
 
     _notifier = notifier;
-    return _provider->subscribe(notifier, flags);
+    return _provider->subscribe(_notifier, flags);
 }
 
 /* Unsubscribe from notifications. */
 
-long FilePager::unsubscribe(l4_cap_idx_t notifier)
+long FilePager::unsubscribe()
 {
-    return _provider->unsubscribe(notifier);
+    if (l4_is_valid_cap(_notifier))
+    {
+        long err = _provider->unsubscribe(_notifier);
+        _notifier = L4_INVALID_CAP;
+        return err;
+    }
+    else
+        return L4_EOK;
 }
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 6e89c2c7fb49 -r 2dd97d71e627 libfsserver/lib/pipes/pipe_pager.cc
--- a/libfsserver/lib/pipes/pipe_pager.cc	Sun Mar 26 01:36:53 2023 +0100
+++ b/libfsserver/lib/pipes/pipe_pager.cc	Sun Mar 26 01:52:16 2023 +0100
@@ -62,7 +62,7 @@
 
     _paging->notify_others(_writing ? PipePaging::WRITER : PipePaging::READER,
                            NOTIFY_PEER_CLOSED, NOTIFY_VALUES_NULL);
-    unsubscribe(_notifier);
+    unsubscribe();
 
     /* Deallocate the paging coordinator if no other endpoints are active. */
 
@@ -183,22 +183,27 @@
 long PipePager::subscribe(l4_cap_idx_t notifier, notify_flags_t flags)
 {
     /* A single notifier is recorded so that it may be unsubscribed when the
-       file is closed. */
+       endpoint is closed. */
 
-    if ((notifier != _notifier) && l4_is_valid_cap(_notifier))
-        unsubscribe(_notifier);
+    unsubscribe();
 
     _notifier = notifier;
-
     return _paging->subscribe(_writing ? PipePaging::WRITER : PipePaging::READER,
-                              notifier, flags);
+                              _notifier, flags);
 }
 
 /* Unsubscribe from notifications. */
 
-long PipePager::unsubscribe(l4_cap_idx_t notifier)
+long PipePager::unsubscribe()
 {
-    return _paging->unsubscribe(notifier);
+    if (l4_is_valid_cap(_notifier))
+    {
+        long err = _paging->unsubscribe(_notifier);
+        _notifier = L4_INVALID_CAP;
+        return err;
+    }
+    else
+        return L4_EOK;
 }
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 6e89c2c7fb49 -r 2dd97d71e627 libnotifier/lib/src/notifier.cc
--- a/libnotifier/lib/src/notifier.cc	Sun Mar 26 01:36:53 2023 +0100
+++ b/libnotifier/lib/src/notifier.cc	Sun Mar 26 01:52:16 2023 +0100
@@ -187,6 +187,13 @@
     state.endpoint = server.config()->server;
   }
 
+  /* Forbid repeated subscription.
+     NOTE: Could instead rely on being unsubscribed, releasing the existing
+           endpoint. */
+
+  else
+    return -L4_EEXIST;
+
   /* Allow this object to be re-entered. This may occur because the subscribe
      operation can cause deferred notifications to be sent back to the
      subscribed notifier and to this object. */
@@ -218,7 +225,7 @@
 
   client_Notification notify(object->base->ref);
 
-  notify.unsubscribe(state.endpoint);
+  notify.unsubscribe();
 
   return remove_endpoint(object, state.endpoint);
 }
diff -r 6e89c2c7fb49 -r 2dd97d71e627 libsystypes/idl/notification.idl
--- a/libsystypes/idl/notification.idl	Sun Mar 26 01:36:53 2023 +0100
+++ b/libsystypes/idl/notification.idl	Sun Mar 26 01:52:16 2023 +0100
@@ -7,7 +7,8 @@
 
   [opcode(23)] void subscribe(in cap notifier, in notify_flags_t flags);
 
-  /* Unsubscribe from events. */
+  /* Unsubscribe from events. A notifier cannot be provided since it will be
+     considered distinct from any previously presented for subscription. */
 
-  [opcode(24)] void unsubscribe(in cap notifier);
+  [opcode(24)] void unsubscribe();
 };