[PATCH] 8390.c: preemption and disable_irq

[Robert Love <rml@tech9.net>]

Jeff,

Alan pointed out to me that drivers/net/8390.c calls disable_irq() while
non-atomic.  This leads to the possibility that the kernel is preempted
while the IRQ line is disabled.

This is not a bug but obviously not optimal.  The solution is simply to
disable preemption prior to calling disable_irq().

Patch against 2.5.40 is attached.  Look OK?

	Robert Love

P.S. Note there is a much simpler solution of merely flipping the
spin_lock() and disable_irq() calls - the spin_lock() will provide the
atomicity without the explicit preempt_disable().  I do not think this
is safe, however, since the IRQ handler could deadlock if it grabbed
this lock (which I assume it does).

diff -urN linux-2.5.40/drivers/net/8390.c linux/drivers/net/8390.c
--- linux-2.5.40/drivers/net/8390.c	Tue Oct  1 03:06:17 2002
+++ linux/drivers/net/8390.c	Tue Oct  1 17:49:11 2002
@@ -243,7 +243,8 @@
 	}
 
 	/* Ugly but a reset can be slow, yet must be protected */
-		
+
+	preempt_disable();
 	disable_irq_nosync(dev->irq);
 	spin_lock(&ei_local->page_lock);
 		
@@ -253,6 +254,7 @@
 		
 	spin_unlock(&ei_local->page_lock);
 	enable_irq(dev->irq);
+	preempt_enable();
 	netif_wake_queue(dev);
 }
     
@@ -286,9 +288,9 @@
 	/*
 	 *	Slow phase with lock held.
 	 */
-	 
+
+	preempt_disable();
 	disable_irq_nosync(dev->irq);
-	
 	spin_lock(&ei_local->page_lock);
 	
 	ei_local->irqlock = 1;
@@ -331,6 +333,7 @@
 		outb_p(ENISR_ALL, e8390_base + EN0_IMR);
 		spin_unlock(&ei_local->page_lock);
 		enable_irq(dev->irq);
+		preempt_enable();
 		ei_local->stat.tx_errors++;
 		return 1;
 	}
@@ -387,6 +390,7 @@
 	
 	spin_unlock(&ei_local->page_lock);
 	enable_irq(dev->irq);
+	preempt_enable();
 
 	dev_kfree_skb (skb);
 	ei_local->stat.tx_bytes += send_length;