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Commit b1766b62 authored by Konrad Rzeszutek Wilk's avatar Konrad Rzeszutek Wilk
Browse files

xen/pciback: Use mutexes when working with Xenbus state transitions. 



The caller that orchestrates the state changes is xenwatch_thread
and it takes a mutex. In our processing of Xenbus states we can take
the luxery of going to sleep on a mutex, so lets do that and
also fix this bug:

BUG: sleeping function called from invalid context at /linux/kernel/mutex.c:271
in_atomic(): 1, irqs_disabled(): 0, pid: 32, name: xenwatch
2 locks held by xenwatch/32:
 #0:  (xenwatch_mutex){......}, at: [<ffffffff813856ab>] xenwatch_thread+0x4b/0x180
 #1:  (&(&pdev->dev_lock)->rlock){......}, at: [<ffffffff8138f05b>] xen_pcibk_disconnect+0x1b/0x80
Pid: 32, comm: xenwatch Not tainted 3.1.0-rc6-00015-g3ce340d #2
Call Trace:
 [<ffffffff810892b2>] __might_sleep+0x102/0x130
 [<ffffffff8163b90f>] mutex_lock_nested+0x2f/0x50
 [<ffffffff81382c1c>] unbind_from_irq+0x2c/0x1b0
 [<ffffffff8110da66>] ? free_irq+0x56/0xb0
 [<ffffffff81382dbc>] unbind_from_irqhandler+0x1c/0x30
 [<ffffffff8138f06b>] xen_pcibk_disconnect+0x2b/0x80
 [<ffffffff81390348>] xen_pcibk_frontend_changed+0xe8/0x140
 [<ffffffff81387ac2>] xenbus_otherend_changed+0xd2/0x150
 [<ffffffff810895c1>] ? get_parent_ip+0x11/0x50
 [<ffffffff81387de0>] frontend_changed+0x10/0x20
 [<ffffffff81385712>] xenwatch_thread+0xb2/0x180

Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 402c5e15

drivers/xen/xen-pciback/pciback.h

+1 −1
Original line number Diff line number Diff line
@@ -29,7 +29,7 @@ struct pci_dev_entry { 


struct xen_pcibk_device {

	void *pci_dev_data;

	spinlock_t dev_lock;

	struct mutex dev_lock;

	struct xenbus_device *xdev;

	struct xenbus_watch be_watch;

	u8 be_watching;

drivers/xen/xen-pciback/xenbus.c

+9 −13
Original line number Diff line number Diff line
@@ -43,7 +43,7 @@ static struct xen_pcibk_device *alloc_pdev(struct xenbus_device *xdev) 
	pdev->xdev = xdev;

	dev_set_drvdata(&xdev->dev, pdev);



	spin_lock_init(&pdev->dev_lock);

	mutex_init(&pdev->dev_lock);



	pdev->sh_info = NULL;

	pdev->evtchn_irq = INVALID_EVTCHN_IRQ;
@@ -61,14 +61,12 @@ static struct xen_pcibk_device *alloc_pdev(struct xenbus_device *xdev) 


static void xen_pcibk_disconnect(struct xen_pcibk_device *pdev)

{

	spin_lock(&pdev->dev_lock);



	mutex_lock(&pdev->dev_lock);

	/* Ensure the guest can't trigger our handler before removing devices */

	if (pdev->evtchn_irq != INVALID_EVTCHN_IRQ) {

		unbind_from_irqhandler(pdev->evtchn_irq, pdev);

		pdev->evtchn_irq = INVALID_EVTCHN_IRQ;

	}

	spin_unlock(&pdev->dev_lock);



	/* If the driver domain started an op, make sure we complete it

	 * before releasing the shared memory */
@@ -76,13 +74,11 @@ static void xen_pcibk_disconnect(struct xen_pcibk_device *pdev) 
	/* Note, the workqueue does not use spinlocks at all.*/

	flush_workqueue(xen_pcibk_wq);



	spin_lock(&pdev->dev_lock);

	if (pdev->sh_info != NULL) {

		xenbus_unmap_ring_vfree(pdev->xdev, pdev->sh_info);

		pdev->sh_info = NULL;

	}

	spin_unlock(&pdev->dev_lock);



	mutex_unlock(&pdev->dev_lock);

}



static void free_pdev(struct xen_pcibk_device *pdev)
@@ -119,9 +115,7 @@ static int xen_pcibk_do_attach(struct xen_pcibk_device *pdev, int gnt_ref, 
		goto out;

	}



	spin_lock(&pdev->dev_lock);

	pdev->sh_info = vaddr;

	spin_unlock(&pdev->dev_lock);



	err = bind_interdomain_evtchn_to_irqhandler(

		pdev->xdev->otherend_id, remote_evtchn, xen_pcibk_handle_event,
@@ -131,10 +125,7 @@ static int xen_pcibk_do_attach(struct xen_pcibk_device *pdev, int gnt_ref, 
				 "Error binding event channel to IRQ");

		goto out;

	}



	spin_lock(&pdev->dev_lock);

	pdev->evtchn_irq = err;

	spin_unlock(&pdev->dev_lock);

	err = 0;



	dev_dbg(&pdev->xdev->dev, "Attached!\n");
@@ -149,6 +140,7 @@ static int xen_pcibk_attach(struct xen_pcibk_device *pdev) 
	char *magic = NULL;





	mutex_lock(&pdev->dev_lock);

	/* Make sure we only do this setup once */

	if (xenbus_read_driver_state(pdev->xdev->nodename) !=

	    XenbusStateInitialised)
@@ -193,6 +185,7 @@ static int xen_pcibk_attach(struct xen_pcibk_device *pdev) 


	dev_dbg(&pdev->xdev->dev, "Connected? %d\n", err);

out:

	mutex_unlock(&pdev->dev_lock);



	kfree(magic);
@@ -368,6 +361,7 @@ static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev) 


	dev_dbg(&pdev->xdev->dev, "Reconfiguring device ...\n");



	mutex_lock(&pdev->dev_lock);

	/* Make sure we only reconfigure once */

	if (xenbus_read_driver_state(pdev->xdev->nodename) !=

	    XenbusStateReconfiguring)
@@ -505,6 +499,7 @@ static int xen_pcibk_reconfigure(struct xen_pcibk_device *pdev) 
	}



out:

	mutex_unlock(&pdev->dev_lock);

	return 0;

}
@@ -561,6 +556,7 @@ static int xen_pcibk_setup_backend(struct xen_pcibk_device *pdev) 
	char dev_str[64];

	char state_str[64];



	mutex_lock(&pdev->dev_lock);

	/* It's possible we could get the call to setup twice, so make sure

	 * we're not already connected.

	 */
@@ -641,10 +637,10 @@ static int xen_pcibk_setup_backend(struct xen_pcibk_device *pdev) 
				 "Error switching to initialised state!");



out:

	mutex_unlock(&pdev->dev_lock);

	if (!err)

		/* see if pcifront is already configured (if not, we'll wait) */

		xen_pcibk_attach(pdev);



	return err;

}