1 files changed, 38 insertions, 32 deletions

diff --git a/arch/um/drivers/chan_user.c b/arch/um/drivers/chan_user.c
index 5d1289d33410..8b81bd5f20f2 100644
--- a/arch/um/drivers/chan_user.c
+++ b/arch/um/drivers/chan_user.c
@@ -51,19 +51,21 @@ error:
 /*
  * UML SIGWINCH handling
  *
- * The point of this is to handle SIGWINCH on consoles which have host ttys and
- * relay them inside UML to whatever might be running on the console and cares
- * about the window size (since SIGWINCH notifies about terminal size changes).
+ * The point of this is to handle SIGWINCH on consoles which have host
+ * ttys and relay them inside UML to whatever might be running on the
+ * console and cares about the window size (since SIGWINCH notifies
+ * about terminal size changes).
  *
- * So, we have a separate thread for each host tty attached to a UML device
- * (side-issue - I'm annoyed that one thread can't have multiple controlling
- * ttys for purposed of handling SIGWINCH, but I imagine there are other reasons
- * that doesn't make any sense).
+ * So, we have a separate thread for each host tty attached to a UML
+ * device (side-issue - I'm annoyed that one thread can't have
+ * multiple controlling ttys for the purpose of handling SIGWINCH, but
+ * I imagine there are other reasons that doesn't make any sense).
  *
- * SIGWINCH can't be received synchronously, so you have to set up to receive it
- * as a signal.  That being the case, if you are going to wait for it, it is
- * convenient to sit in sigsuspend() and wait for the signal to bounce you out of
- * it (see below for how we make sure to exit only on SIGWINCH).
+ * SIGWINCH can't be received synchronously, so you have to set up to
+ * receive it as a signal.  That being the case, if you are going to
+ * wait for it, it is convenient to sit in sigsuspend() and wait for
+ * the signal to bounce you out of it (see below for how we make sure
+ * to exit only on SIGWINCH).
  */
 
 static void winch_handler(int sig)
@@ -112,7 +114,8 @@ static int winch_thread(void *arg)
 
         err = os_new_tty_pgrp(pty_fd, os_getpid());
         if(err < 0){
-                printk("winch_thread : new_tty_pgrp failed, err = %d\n", -err);
+                printk("winch_thread : new_tty_pgrp failed on fd %d, "
+                       "err = %d\n", pty_fd, -err);
                 exit(1);
         }
 
@@ -126,8 +129,9 @@ static int winch_thread(void *arg)
                        "err = %d\n", -count);
 
         while(1){
-                /* This will be interrupted by SIGWINCH only, since other signals
-                 * are blocked.*/
+                /* This will be interrupted by SIGWINCH only, since
+                 * other signals are blocked.
+                 */
                 sigsuspend(&sigs);
 
                 count = os_write_file(pipe_fd, &c, sizeof(c));
@@ -137,10 +141,10 @@ static int winch_thread(void *arg)
         }
 }
 
-static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out)
+static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out,
+                       unsigned long *stack_out)
 {
         struct winch_data data;
-        unsigned long stack;
         int fds[2], n, err;
         char c;
 
@@ -153,9 +157,11 @@ static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out)
         data = ((struct winch_data) { .pty_fd           = fd,
                                       .pipe_fd          = fds[1] } );
         /* CLONE_FILES so this thread doesn't hold open files which are open
-         * now, but later closed.  This is a problem with /dev/net/tun.
+         * now, but later closed in a different thread.  This is a
+         * problem with /dev/net/tun, which if held open by this
+         * thread, prevents the TUN/TAP device from being reused.
          */
-        err = run_helper_thread(winch_thread, &data, CLONE_FILES, &stack, 0);
+        err = run_helper_thread(winch_thread, &data, CLONE_FILES, stack_out, 0);
         if(err < 0){
                 printk("fork of winch_thread failed - errno = %d\n", -err);
                 goto out_close;
@@ -187,25 +193,25 @@ static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out)
 
 void register_winch(int fd, struct tty_struct *tty)
 {
-        int pid, thread, thread_fd = -1;
-        int count;
+        unsigned long stack;
+        int pid, thread, count, thread_fd = -1;
         char c = 1;
 
         if(!isatty(fd))
                 return;
 
         pid = tcgetpgrp(fd);
-        if(!CHOOSE_MODE_PROC(is_tracer_winch, is_skas_winch, pid, fd,
-                             tty) && (pid == -1)){
-                thread = winch_tramp(fd, tty, &thread_fd);
-                if(thread > 0){
-                        register_winch_irq(thread_fd, fd, thread, tty);
-
-                        count = os_write_file(thread_fd, &c, sizeof(c));
-                        if(count != sizeof(c))
-                                printk("register_winch : failed to write "
-                                       "synchronization byte, err = %d\n",
-                                        -count);
-                }
+        if (!CHOOSE_MODE_PROC(is_tracer_winch, is_skas_winch, pid, fd, tty) &&
+            (pid == -1)) {
+                thread = winch_tramp(fd, tty, &thread_fd, &stack);
+                if (thread < 0)
+                        return;
+
+                register_winch_irq(thread_fd, fd, thread, tty, stack);
+
+                count = os_write_file(thread_fd, &c, sizeof(c));
+                if(count != sizeof(c))
+                        printk("register_winch : failed to write "
+                               "synchronization byte, err = %d\n", -count);
         }
 }