From 213d36cead9d4b94a406af47c7749355c0d3a3f2 Mon Sep 17 00:00:00 2001
From: NIIBE Yutaka <gniibe@fsij.org>
Date: Tue, 17 Mar 2020 14:00:31 +0900
Subject: [PATCH] watch: use condition variable.

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
---
 scd/app.c      | 31 +++++++++++++++++++++++++++++++
 scd/command.c  | 40 ++++++++++++++++++++--------------------
 scd/scdaemon.c |  3 +++
 scd/scdaemon.h |  2 ++
 4 files changed, 56 insertions(+), 20 deletions(-)

diff --git a/scd/app.c b/scd/app.c
index 7193d0ba7..da70f8705 100644
--- a/scd/app.c
+++ b/scd/app.c
@@ -42,6 +42,9 @@ send_serialno_and_app_status (card_t card, int with_apps, ctrl_t ctrl);
  * applications.  */
 static npth_mutex_t card_list_lock;
 
+/* Notification to threads which keep watching the status change.  */
+static npth_cond_t notify_cond;
+
 /* A list of card contexts.  A card is a collection of applications
  * (described by app_t) on the same physical token. */
 static card_t card_top;
@@ -2013,10 +2016,19 @@ initialize_module_command (void)
       return err;
     }
 
+  err = npth_cond_init (&notify_cond, NULL);
+  if (err)
+    {
+      err = gpg_error_from_syserror ();
+      log_error ("npth_cond_init failed: %s\n", gpg_strerror (err));
+      return;
+    }
+
   return apdu_init ();
 }
 
 
+
 /* Sort helper for app_send_card_list.  */
 static int
 compare_card_list_items (const void *arg_a, const void *arg_b)
@@ -2279,3 +2291,22 @@ app_do_with_keygrip (ctrl_t ctrl, int action, const char *keygrip_str,
   npth_mutex_unlock (&card_list_lock);
   return c;
 }
+
+void
+app_notify (void)
+{
+  npth_cond_broadcast (&notify_cond);
+}
+
+int
+app_wait (void)
+{
+  int ret;
+
+  npth_mutex_lock (&card_list_lock);
+  npth_cond_wait (&notify_cond, &card_list_lock);
+  ret = (card_top == NULL);
+  npth_mutex_unlock (&card_list_lock);
+
+  return ret;
+}
diff --git a/scd/command.c b/scd/command.c
index 1c88b384d..f611c1ea6 100644
--- a/scd/command.c
+++ b/scd/command.c
@@ -2158,35 +2158,35 @@ cmd_list_device (assuan_context_t ctx, char *line)
   int watch = 0;
 
   if (has_option (line, "--watch"))
-    watch = 1;
+    {
+      watch = 1;
+      ctrl->server_local->watching_status = 1;
+    }
 
+  /* Clear the remove flag so that the open_card is able to reread it.  */
+  if (ctrl->server_local->card_removed)
+    ctrl->server_local->card_removed = 0;
+
+  /* Then, actively try to open device(s) available.  */
   if ((err = open_card (ctrl)))
     return err;
 
+  /* Remove reference(s) to the card.  */
+  ctrl->card_ctx = NULL;
+  ctrl->current_apptype = APPTYPE_NONE;
+  card_unref (ctrl->card_ctx);
+
   if (watch)
-    {
-      ctrl->server_local->watching_status = 1;
-      while (1)
+    while (1)
+      if (app_wait ())
         {
-          int sig;
-
-          npth_unprotect ();
-          sigwait (npth_sigev_sigmask (), &sig);
-          npth_protect ();
-
-          assuan_write_status (ctx, "signal", "");
-
-          if (ctrl->server_local->card_removed)
-            {
-              ctrl->server_local->watching_status = 0;
-              return 0;
-            }
+          ctrl->server_local->watching_status = 0;
+          return 0;
         }
-    }
+      else
+        assuan_write_status (ctx, "app_wait", "... returns");
 
-  /* XXX: Actively try to open devices available.  */
   return gpg_error (GPG_ERR_NOT_FOUND);
-  return 0;
 }
 
 /* Return true if the command CMD implements the option OPT.  */
diff --git a/scd/scdaemon.c b/scd/scdaemon.c
index b7bbc0361..1f34809bc 100644
--- a/scd/scdaemon.c
+++ b/scd/scdaemon.c
@@ -1220,6 +1220,9 @@ scd_kick_the_loop (void)
     log_error ("SetEvent for scd_kick_the_loop failed: %s\n",
                gpg_strerror (gpg_error_from_syserror ()));
 #endif
+
+  /* Also, notify watching threads.  */
+  app_notify ();
 }
 
 /* Connection handler loop.  Wait for connection requests and spawn a
diff --git a/scd/scdaemon.h b/scd/scdaemon.h
index 391f16578..c79c272a0 100644
--- a/scd/scdaemon.h
+++ b/scd/scdaemon.h
@@ -153,5 +153,7 @@ int get_active_connection_count (void);
 
 /*-- app.c --*/
 int scd_update_reader_status_file (void);
+int app_wait (void);
+void app_notify (void);
 
 #endif /*SCDAEMON_H*/