Commit 71c8d4c3 authored Jan 18, 2006 by Paolo 'Blaisorblade' Giarrusso Committed by Linus Torvalds Jan 18, 2006

[PATCH] uml: fix spinlock recursion and sleep-inside-spinlock in error path



In this error path, when the interface has had a problem, we call dev_close(),
which is disallowed for two reasons:

*) takes again the UML internal spinlock, inside the ->stop method of this
   device
*) can be called in process context only, while we're in interrupt context.

I've also thought that calling dev_close() may be a wrong policy to follow,
but it's not up to me to decide that.

However, we may end up with multiple dev_close() queued on the same device.
But the initial test for (dev->flags & IFF_UP) makes this harmless, though -
and dev_close() is supposed to care about races with itself.  So there's no
harm in delaying the shutdown, IMHO.

Something to mark the interface as "going to shutdown" would be appreciated,
but dev_deactivate has the same problems as dev_close(), so we can't use it
either.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent e56a7885

arch/um/drivers/net_kern.c

+13 −2

Original line number	Diff line number	Diff line
		@@ -68,6 +68,11 @@ static int uml_net_rx(struct net_device *dev)
		return pkt_len;
		}

		static void uml_dev_close(void* dev)
		{
		dev_close( (struct net_device *) dev);
		}

		irqreturn_t uml_net_interrupt(int irq, void dev_id, struct pt_regs regs)
		{
		struct net_device *dev = dev_id;
		@@ -80,10 +85,16 @@ irqreturn_t uml_net_interrupt(int irq, void dev_id, struct pt_regs regs)
		spin_lock(&lp->lock);
		while((err = uml_net_rx(dev)) > 0) ;
		if(err < 0) {
		DECLARE_WORK(close_work, uml_dev_close, dev);
		printk(KERN_ERR
		"Device '%s' read returned %d, shutting it down\n",
		dev->name, err);
		dev_close(dev);
		/* dev_close can't be called in interrupt context, and takes
		* again lp->lock.
		* And dev_close() can be safely called multiple times on the
		* same device, since it tests for (dev->flags & IFF_UP). So
		* there's no harm in delaying the device shutdown. */
		schedule_work(&close_work);
		goto out;
		}
		reactivate_fd(lp->fd, UM_ETH_IRQ);

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