# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1677446371 -3600
# Node ID d9de8ecdaf6038c8d2d6a31d021a520ac588e143
# Parent  4f4174ed0b1f99a81e6a0367e7426626e2a46431
Changed the unsubscribe operation in the notification interface to involve an
explicit notifier, thus relieving the external pager from having to retain a
single notifier when many notifiers could potentially be used. For file and
pipe pagers, the use of a single notifier per pager is preserved but managed
slightly differently.

diff -r 4f4174ed0b1f -r d9de8ecdaf60 libexec/include/exec/external_pager.h
--- a/libexec/include/exec/external_pager.h	Sun Feb 26 18:43:52 2023 +0100
+++ b/libexec/include/exec/external_pager.h	Sun Feb 26 22:19:31 2023 +0100
@@ -34,9 +34,6 @@
 class ExternalPager : public ExecPager, public ParentPagerObject,
                       public NotificationSupport
 {
-protected:
-  l4_cap_idx_t _notifier;
-
 public:
   explicit ExternalPager(address_t start = 0, address_t end = 0);
 
@@ -61,7 +58,7 @@
 
   virtual long subscribe(l4_cap_idx_t notifier, notify_flags_t flags);
 
-  virtual long unsubscribe();
+  virtual long unsubscribe(l4_cap_idx_t notifier);
 };
 
 /* vim: tabstop=2 expandtab shiftwidth=2
diff -r 4f4174ed0b1f -r d9de8ecdaf60 libexec/lib/src/external_pager.cc
--- a/libexec/lib/src/external_pager.cc	Sun Feb 26 18:43:52 2023 +0100
+++ b/libexec/lib/src/external_pager.cc	Sun Feb 26 22:19:31 2023 +0100
@@ -172,16 +172,14 @@
 
 long ExternalPager::subscribe(l4_cap_idx_t notifier, notify_flags_t flags)
 {
-  _notifier = notifier;
   return NotificationSupport::subscribe(notifier, flags);
 }
 
 /* Unsubscribe from notifications. */
 
-long ExternalPager::unsubscribe()
+long ExternalPager::unsubscribe(l4_cap_idx_t notifier)
 {
-  NotificationSupport::unsubscribe(_notifier);
-  return L4_EOK;
+  return NotificationSupport::unsubscribe(notifier);
 }
 
 /* vim: tabstop=2 expandtab shiftwidth=2
diff -r 4f4174ed0b1f -r d9de8ecdaf60 libfsclient/lib/src/notifier.cc
--- a/libfsclient/lib/src/notifier.cc	Sun Feb 26 18:43:52 2023 +0100
+++ b/libfsclient/lib/src/notifier.cc	Sun Feb 26 22:19:31 2023 +0100
@@ -216,7 +216,7 @@
 
   client_Notification notify(object->base->ref);
 
-  notify.unsubscribe();
+  notify.unsubscribe(endpoint);
 
   return remove_endpoint(object, endpoint);
 }
diff -r 4f4174ed0b1f -r d9de8ecdaf60 libfsserver/include/fsserver/directory_resource.h
--- a/libfsserver/include/fsserver/directory_resource.h	Sun Feb 26 18:43:52 2023 +0100
+++ b/libfsserver/include/fsserver/directory_resource.h	Sun Feb 26 22:19:31 2023 +0100
@@ -63,7 +63,7 @@
 
     virtual long subscribe(l4_cap_idx_t notifier, notify_flags_t flags);
 
-    virtual long unsubscribe();
+    virtual long unsubscribe(l4_cap_idx_t notifier);
 };
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 4f4174ed0b1f -r d9de8ecdaf60 libfsserver/include/fsserver/file_pager.h
--- a/libfsserver/include/fsserver/file_pager.h	Sun Feb 26 18:43:52 2023 +0100
+++ b/libfsserver/include/fsserver/file_pager.h	Sun Feb 26 22:19:31 2023 +0100
@@ -83,7 +83,7 @@
 
     virtual long subscribe(l4_cap_idx_t notifier, notify_flags_t flags);
 
-    virtual long unsubscribe();
+    virtual long unsubscribe(l4_cap_idx_t notifier);
 };
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 4f4174ed0b1f -r d9de8ecdaf60 libfsserver/include/fsserver/notification.h
--- a/libfsserver/include/fsserver/notification.h	Sun Feb 26 18:43:52 2023 +0100
+++ b/libfsserver/include/fsserver/notification.h	Sun Feb 26 22:19:31 2023 +0100
@@ -121,7 +121,7 @@
     virtual long subscribe(unsigned int endpoint, l4_cap_idx_t notifier,
                            notify_flags_t flags);
 
-    virtual void unsubscribe(l4_cap_idx_t notifier);
+    virtual long unsubscribe(l4_cap_idx_t notifier);
 };
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 4f4174ed0b1f -r d9de8ecdaf60 libfsserver/include/fsserver/pipe_pager.h
--- a/libfsserver/include/fsserver/pipe_pager.h	Sun Feb 26 18:43:52 2023 +0100
+++ b/libfsserver/include/fsserver/pipe_pager.h	Sun Feb 26 22:19:31 2023 +0100
@@ -77,7 +77,7 @@
 
     virtual long subscribe(l4_cap_idx_t notifier, notify_flags_t flags);
 
-    virtual long unsubscribe();
+    virtual long unsubscribe(l4_cap_idx_t notifier);
 };
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 4f4174ed0b1f -r d9de8ecdaf60 libfsserver/lib/directories/directory_resource.cc
--- a/libfsserver/lib/directories/directory_resource.cc	Sun Feb 26 18:43:52 2023 +0100
+++ b/libfsserver/lib/directories/directory_resource.cc	Sun Feb 26 22:19:31 2023 +0100
@@ -131,10 +131,9 @@
 
 /* Unsubscribe from notifications. */
 
-long DirectoryResource::unsubscribe()
+long DirectoryResource::unsubscribe(l4_cap_idx_t notifier)
 {
-    _provider->unsubscribe(_notifier);
-    return L4_EOK;
+    return _provider->unsubscribe(notifier);
 }
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 4f4174ed0b1f -r d9de8ecdaf60 libfsserver/lib/files/file_pager.cc
--- a/libfsserver/lib/files/file_pager.cc	Sun Feb 26 18:43:52 2023 +0100
+++ b/libfsserver/lib/files/file_pager.cc	Sun Feb 26 22:19:31 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();
+    unsubscribe(_notifier);
 
     /* Detach the pager, potentially removing the file provider. */
 
@@ -146,24 +146,27 @@
 
 
 
-/* Subscribe to notifications. */
+/* Subscribe to notifications.
+   Readers can subscribe to new data (flush) and file closed events.
+   Writers can subscribe to file closed events. */
 
 long FilePager::subscribe(l4_cap_idx_t notifier, notify_flags_t flags)
 {
-    /* Readers can subscribe to new data (flush) and file closed events.
-       Writers can subscribe to file closed events. */
+    /* 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);
 
     _notifier = notifier;
-
     return _provider->subscribe(notifier, flags);
 }
 
 /* Unsubscribe from notifications. */
 
-long FilePager::unsubscribe()
+long FilePager::unsubscribe(l4_cap_idx_t notifier)
 {
-    _provider->unsubscribe(_notifier);
-    return L4_EOK;
+    return _provider->unsubscribe(notifier);
 }
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 4f4174ed0b1f -r d9de8ecdaf60 libfsserver/lib/generic/notification.cc
--- a/libfsserver/lib/generic/notification.cc	Sun Feb 26 18:43:52 2023 +0100
+++ b/libfsserver/lib/generic/notification.cc	Sun Feb 26 22:19:31 2023 +0100
@@ -103,11 +103,12 @@
 
 /* Unsubscribe from an endpoint's notifications. */
 
-void NotificationSupport::unsubscribe(l4_cap_idx_t notifier)
+long NotificationSupport::unsubscribe(l4_cap_idx_t notifier)
 {
     std::lock_guard<std::mutex> guard(_lock);
 
     _unsubscribe(notifier);
+    return L4_EOK;
 }
 
 /* Common subscription functionality. */
diff -r 4f4174ed0b1f -r d9de8ecdaf60 libfsserver/lib/pipes/pipe_pager.cc
--- a/libfsserver/lib/pipes/pipe_pager.cc	Sun Feb 26 18:43:52 2023 +0100
+++ b/libfsserver/lib/pipes/pipe_pager.cc	Sun Feb 26 22:19:31 2023 +0100
@@ -64,7 +64,7 @@
 
     _paging->notify_others(_writing ? PipePaging::WRITER : PipePaging::READER,
                            NOTIFY_PEER_CLOSED, NOTIFY_VALUES_NULL);
-    unsubscribe();
+    unsubscribe(_notifier);
 
     /* Deallocate the paging coordinator if no other endpoints are active. */
 
@@ -178,12 +178,17 @@
 
 
 
-/* Subscribe to notifications. */
+/* Subscribe to notifications.
+   Readers can subscribe to new data (at end), and pipe closed events.
+   Writers can subscribe to new space and pipe closed events. */
 
 long PipePager::subscribe(l4_cap_idx_t notifier, notify_flags_t flags)
 {
-    /* Readers can subscribe to new data (at end), and pipe closed events.
-       Writers can subscribe to new space and pipe closed events. */
+    /* 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);
 
     _notifier = notifier;
 
@@ -193,10 +198,9 @@
 
 /* Unsubscribe from notifications. */
 
-long PipePager::unsubscribe()
+long PipePager::unsubscribe(l4_cap_idx_t notifier)
 {
-    _paging->unsubscribe(_notifier);
-    return L4_EOK;
+    return _paging->unsubscribe(notifier);
 }
 
 // vim: tabstop=4 expandtab shiftwidth=4
diff -r 4f4174ed0b1f -r d9de8ecdaf60 libsystypes/idl/notification.idl
--- a/libsystypes/idl/notification.idl	Sun Feb 26 18:43:52 2023 +0100
+++ b/libsystypes/idl/notification.idl	Sun Feb 26 22:19:31 2023 +0100
@@ -9,5 +9,5 @@
 
   /* Unsubscribe from events. */
 
-  [opcode(24)] void unsubscribe();
+  [opcode(24)] void unsubscribe(in cap notifier);
 };