[PATCH] ATM locking fix. [Re: [PATCH] spinlock not locked when unlocking in atm_dev_register]

From: Maksim Krasnyanskiy (maxk@qualcomm.com)
Date: Thu Mar 07 2002 - 17:11:37 EST


Hi Folks,

Some time ago I promised a patch that fixes ATM device allocation code.
Fix that Alan's got in his 2.4.19-pre2-ac3 is wrong because it just removes
locking instead of fixing it.
So here goes my patch. Tested on dual Athlon box.

Marcelo, Alan, please apply.

Patch URL:
        http://bluez.sf.net/atm.patch-2.4.19-pre2.gz

--- linux/net/atm/resources.c.orig Thu Mar 7 13:56:00 2002
+++ linux/net/atm/resources.c Thu Mar 7 13:56:40 2002
@@ -32,7 +32,7 @@
  {
          struct atm_dev *dev;

- dev = kmalloc(sizeof(*dev),GFP_KERNEL);
+ dev = kmalloc(sizeof(*dev), GFP_ATOMIC);
          if (!dev) return NULL;
          memset(dev,0,sizeof(*dev));
          dev->type = type;
@@ -40,32 +40,24 @@
          dev->link_rate = ATM_OC3_PCR;
          dev->next = NULL;

- spin_lock(&atm_dev_lock);
-
          dev->prev = last_dev;

          if (atm_devs) last_dev->next = dev;
          else atm_devs = dev;
          last_dev = dev;
- spin_unlock(&atm_dev_lock);
          return dev;
  }

  static void free_atm_dev(struct atm_dev *dev)
  {
- spin_lock (&atm_dev_lock);
-
          if (dev->prev) dev->prev->next = dev->next;
          else atm_devs = dev->next;
          if (dev->next) dev->next->prev = dev->prev;
          else last_dev = dev->prev;
          kfree(dev);
-
- spin_unlock (&atm_dev_lock);
  }

-
  struct atm_dev *atm_find_dev(int number)
  {
          struct atm_dev *dev;
@@ -75,17 +67,18 @@
          return NULL;
  }

-
  struct atm_dev *atm_dev_register(const char *type,const struct atmdev_ops
*ops,
      int number,atm_dev_flags_t *flags)
  {
- struct atm_dev *dev;
+ struct atm_dev *dev = NULL;
+
+ spin_lock(&atm_dev_lock);

          dev = alloc_atm_dev(type);
          if (!dev) {
                  printk(KERN_ERR "atm_dev_register: no space for dev %s\n",
                      type);
- return NULL;
+ goto done;
          }
          if (number != -1) {
                  if (atm_find_dev(number)) {
@@ -93,8 +86,7 @@
                          return NULL;
                  }
                  dev->number = number;
- }
- else {
+ } else {
                  dev->number = 0;
                  while (atm_find_dev(dev->number)) dev->number++;
          }
@@ -102,20 +94,23 @@
          dev->dev_data = NULL;
          barrier();
          dev->ops = ops;
- if (flags) dev->flags = *flags;
- else memset(&dev->flags,0,sizeof(dev->flags));
+ if (flags)
+ dev->flags = *flags;
+ else
+ memset(&dev->flags,0,sizeof(dev->flags));
          memset((void *) &dev->stats,0,sizeof(dev->stats));
  #ifdef CONFIG_PROC_FS
          if (ops->proc_read)
                  if (atm_proc_dev_register(dev) < 0) {
                          printk(KERN_ERR "atm_dev_register: "
                              "atm_proc_dev_register failed for dev %s\n",type);
- spin_unlock (&atm_dev_lock);
                          free_atm_dev(dev);
- return NULL;
+ goto done;
                  }
  #endif
- spin_unlock (&atm_dev_lock);
+
+done:
+ spin_unlock(&atm_dev_lock);
          return dev;
  }

@@ -125,10 +120,11 @@
  #ifdef CONFIG_PROC_FS
          if (dev->ops->proc_read) atm_proc_dev_deregister(dev);
  #endif
+ spin_lock(&atm_dev_lock);
          free_atm_dev(dev);
+ spin_unlock(&atm_dev_lock);
  }

-
  void shutdown_atm_dev(struct atm_dev *dev)
  {
          if (dev->vccs) {
@@ -146,7 +142,6 @@
          kfree(sk->protinfo.af_atm);
  }

-
  struct sock *alloc_atm_vcc_sk(int family)
  {
          struct sock *sk;

-
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This archive was generated by hypermail 2b29 : Thu Mar 07 2002 - 21:01:10 EST