Mirror USB backend fixes (Issue #1461)

diff --git a/backend/usb-libusb.c b/backend/usb-libusb.c
index 181ba6cb0022a88a776b0a582383c4e94e297ee3..51852b658f01ee029f7d3020548c6a4a74a81a42 100644 (file)
--- a/backend/usb-libusb.c
+++ b/backend/usb-libusb.c
@@ -78,6 +78,8 @@ typedef struct usb_globals_s          /* Global USB printer information */
   pthread_cond_t       sidechannel_thread_cond;
   int                  sidechannel_thread_stop;
   int                  sidechannel_thread_done;
+
+  int                  wakeup_pipe[2]; /* Pipe for waking up select() in the main thread */
 } usb_globals_t;
 
 /*
@@ -191,12 +193,14 @@ print_device(const char *uri,             /* I - Device URI */
                *print_ptr;             /* Pointer into print data buffer */
   fd_set       input_set;              /* Input set for select() */
   int          nfds;                   /* Number of file descriptors */
+  int          nfd_max;                /* Maximum file descriptor number for select() */
   struct timeval *timeout,             /* Timeout pointer */
                tv;                     /* Time value */
   struct timespec cond_timeout;                /* pthread condition timeout */
   int          num_opts;               /* Number of options */
   cups_option_t        *opts;                  /* Options */
   const char   *val;                   /* Option value */
+  char         dummy;                  /* select() wakeup bogus data */
 
 
   load_quirks();
@@ -208,6 +212,17 @@ print_device(const char *uri,              /* I - Device URI */
   have_sidechannel = !fstat(CUPS_SC_FD, &sidechannel_info) &&
                      S_ISSOCK(sidechannel_info.st_mode);
 
+ /*
+  * Create a pipe for waking up the main thread from select()...
+  */
+
+  if (pipe(g.wakeup_pipe) < 0)
+  {
+    fprintf(stderr, "DEBUG: Unable to create wakeup pipe - %s\n",
+           strerror(errno));
+    return (CUPS_BACKEND_STOP);
+  }
+
   g.wait_eof = WAIT_EOF;
 
  /*
@@ -349,12 +364,15 @@ print_device(const char *uri,             /* I - Device URI */
       lseek(print_fd, 0, SEEK_SET);
     }
 
+    nfd_max = (print_fd > g.wakeup_pipe[0] ? print_fd : g.wakeup_pipe[0]) + 1;
+
     while (status == CUPS_BACKEND_OK)
     {
       FD_ZERO(&input_set);
 
       if (!g.print_bytes)
        FD_SET(print_fd, &input_set);
+      FD_SET(g.wakeup_pipe[0], &input_set);
 
      /*
       * Calculate select timeout...
@@ -387,7 +405,7 @@ print_device(const char *uri,               /* I - Device URI */
       pthread_cond_signal(&g.readwrite_lock_cond);
       pthread_mutex_unlock(&g.readwrite_lock_mutex);
 
-      nfds = select(print_fd + 1, &input_set, NULL, NULL, timeout);
+      nfds = select(nfd_max, &input_set, NULL, NULL, timeout);
 
      /*
       * Reacquire the lock...
@@ -418,6 +436,13 @@ print_device(const char *uri,              /* I - Device URI */
        }
       }
 
+     /*
+      * Check if we were woken up by the sidechannel thread...
+      */
+
+      if (FD_ISSET(g.wakeup_pipe[0], &input_set))
+       read(g.wakeup_pipe[0], &dummy, 1);
+
      /*
       * If drain output has finished send a response...
       */
@@ -425,8 +450,8 @@ print_device(const char *uri,               /* I - Device URI */
       if (g.drain_output && !nfds && !g.print_bytes)
       {
        /* Send a response... */
-       cupsSideChannelWrite(CUPS_SC_CMD_DRAIN_OUTPUT, CUPS_SC_STATUS_OK, NULL, 0, 1.0);
        g.drain_output = 0;
+       cupsSideChannelWrite(CUPS_SC_CMD_DRAIN_OUTPUT, CUPS_SC_STATUS_OK, NULL, 0, 1.0);
       }
 
      /*
@@ -644,6 +669,13 @@ print_device(const char *uri,              /* I - Device URI */
 
   close_device(g.printer);
 
+ /*
+  * Close the wakeup pipe...
+  */
+
+  close(g.wakeup_pipe[0]);
+  close(g.wakeup_pipe[1]);
+
  /*
   * Clean up ....
   */
@@ -1899,6 +1931,17 @@ sidechannel_thread(void *reference)
                stderr);
 
          g.drain_output = 1;
+         pthread_mutex_lock(&g.readwrite_lock_mutex);
+         if (!g.readwrite_lock)
+         {
+          /*
+           * If main thread is inside select(), assume it has infinite
+           * timeout and needs to be woken up.
+           */
+           if (write(g.wakeup_pipe[1], &data, 1) < 0)
+             fputs("DEBUG: Error writing to wakeup pipe\n", stderr);
+         }
+         pthread_mutex_unlock(&g.readwrite_lock_mutex);
          break;
 
       case CUPS_SC_CMD_GET_BIDI:       /* Is the connection bidirectional? */