2.4.1

 drivers

 net

diff -u --recursive --new-file v2.4.0/linux/drivers/net/ppp_async.c linux/drivers/net/ppp_async.c
--- v2.4.0/linux/drivers/net/ppp_async.c   Fri Apr 21 13:31:10 2000
+++ linux/drivers/net/ppp_async.c   Mon Jan 15 11:04:57 2001
@@ -33,13 +33,6 @@
 #include <linux/init.h>
 #include <asm/uaccess.h>
 
-#ifndef spin_trylock_bh
-#define spin_trylock_bh(lock)   ({ int __r; local_bh_disable();   \
-               __r = spin_trylock(lock);   \
-               if (!__r) local_bh_enable();   \
-               __r; })
-#endif
-
 #define PPP_VERSION   "2.4.1"
 
 #define OBUFSIZE   256
@@ -76,6 +69,7 @@
 /* Bit numbers in xmit_flags */
 #define XMIT_WAKEUP   0
 #define XMIT_FULL   1
+#define XMIT_BUSY   2
 
 /* State bits */
 #define SC_TOSS      0x20000000
@@ -181,18 +175,14 @@
 }
 
 /*
- * Read does nothing.
+ * Read does nothing - no data is ever available this way.
+ * Pppd reads and writes packets via /dev/ppp instead.
  */
 static ssize_t
 ppp_asynctty_read(struct tty_struct *tty, struct file *file,
         unsigned char *buf, size_t count)
 {
-   /* For now, do the same as the old 2.3.x code useta */
-   struct asyncppp *ap = tty->disc_data;
-
-   if (ap == 0)
-      return -ENXIO;
-   return ppp_channel_read(&ap->chan, file, buf, count);
+   return -EAGAIN;
 }
 
 /*
@@ -203,12 +193,7 @@
 ppp_asynctty_write(struct tty_struct *tty, struct file *file,
          const unsigned char *buf, size_t count)
 {
-   /* For now, do the same as the old 2.3.x code useta */
-   struct asyncppp *ap = tty->disc_data;
-
-   if (ap == 0)
-      return -ENXIO;
-   return ppp_channel_write(&ap->chan, buf, count);
+   return -EAGAIN;
 }
 
 static int
@@ -259,25 +244,6 @@
       err = 0;
       break;
 
-/*
- * For now, do the same as the old 2.3 driver useta
- */
-   case PPPIOCGFLAGS:
-   case PPPIOCSFLAGS:
-   case PPPIOCGASYNCMAP:
-   case PPPIOCSASYNCMAP:
-   case PPPIOCGRASYNCMAP:
-   case PPPIOCSRASYNCMAP:
-   case PPPIOCGXASYNCMAP:
-   case PPPIOCSXASYNCMAP:
-   case PPPIOCGMRU:
-   case PPPIOCSMRU:
-      err = -EPERM;
-      if (!capable(CAP_NET_ADMIN))
-         break;
-      err = ppp_async_ioctl(&ap->chan, cmd, arg);
-      break;
-
    case PPPIOCATTACH:
    case PPPIOCDETACH:
       err = ppp_channel_ioctl(&ap->chan, cmd, arg);
@@ -294,18 +260,7 @@
 static unsigned int
 ppp_asynctty_poll(struct tty_struct *tty, struct file *file, poll_table *wait)
 {
-   unsigned int mask;
-   struct asyncppp *ap = tty->disc_data;
-
-   mask = POLLOUT | POLLWRNORM;
-/*
- * For now, do the same as the old 2.3 driver useta
- */
-   if (ap != 0)
-      mask |= ppp_channel_poll(&ap->chan, file, wait);
-   if (test_bit(TTY_OTHER_CLOSED, &tty->flags) || tty_hung_up_p(file))
-      mask |= POLLHUP;
-   return mask;
+   return 0;
 }
 
 static int
@@ -637,8 +592,18 @@
    int tty_stuffed = 0;
 
    set_bit(XMIT_WAKEUP, &ap->xmit_flags);
-   if (!spin_trylock_bh(&ap->xmit_lock))
+   /*
+    * We can get called recursively here if the tty write
+    * function calls our wakeup function.  This can happen
+    * for example on a pty with both the master and slave
+    * set to PPP line discipline.
+    * We use the XMIT_BUSY bit to detect this and get out,
+    * leaving the XMIT_WAKEUP bit set to tell the other
+    * instance that it may now be able to write more now.
+    */
+   if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
       return 0;
+   spin_lock_bh(&ap->xmit_lock);
    for (;;) {
       if (test_and_clear_bit(XMIT_WAKEUP, &ap->xmit_flags))
          tty_stuffed = 0;
@@ -653,7 +618,7 @@
             tty_stuffed = 1;
          continue;
       }
-      if (ap->optr == ap->olim && ap->tpkt != 0) {
+      if (ap->optr >= ap->olim && ap->tpkt != 0) {
          if (ppp_async_encode(ap)) {
             /* finished processing ap->tpkt */
             clear_bit(XMIT_FULL, &ap->xmit_flags);
@@ -661,17 +626,29 @@
          }
          continue;
       }
-      /* haven't made any progress */
-      spin_unlock_bh(&ap->xmit_lock);
+      /*
+       * We haven't made any progress this time around.
+       * Clear XMIT_BUSY to let other callers in, but
+       * after doing so we have to check if anyone set
+       * XMIT_WAKEUP since we last checked it.  If they
+       * did, we should try again to set XMIT_BUSY and go
+       * around again in case XMIT_BUSY was still set when
+       * the other caller tried.
+       */
+      clear_bit(XMIT_BUSY, &ap->xmit_flags);
+      /* any more work to do? if not, exit the loop */
       if (!(test_bit(XMIT_WAKEUP, &ap->xmit_flags)
             || (!tty_stuffed && ap->tpkt != 0)))
          break;
-      if (!spin_trylock_bh(&ap->xmit_lock))
+      /* more work to do, see if we can do it now */
+      if (test_and_set_bit(XMIT_BUSY, &ap->xmit_flags))
          break;
    }
+   spin_unlock_bh(&ap->xmit_lock);
    return done;
 
 flush:
+   clear_bit(XMIT_BUSY, &ap->xmit_flags);
    if (ap->tpkt != 0) {
       kfree_skb(ap->tpkt);
       ap->tpkt = 0;