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Subject[PATCH 1/2] xen/pciback: Use mutexes when working with Xenbus state transitions.
Date
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: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
drivers/xen/xen-pciback/pciback.h | 2 +-
drivers/xen/xen-pciback/xenbus.c | 22 +++++++++-------------
2 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/drivers/xen/xen-pciback/pciback.h b/drivers/xen/xen-pciback/pciback.h
index d095acd..e9b4011 100644
--- a/drivers/xen/xen-pciback/pciback.h
+++ b/drivers/xen/xen-pciback/pciback.h
@@ -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;
diff --git a/drivers/xen/xen-pciback/xenbus.c b/drivers/xen/xen-pciback/xenbus.c
index 522f2da..474d52e 100644
--- a/drivers/xen/xen-pciback/xenbus.c
+++ b/drivers/xen/xen-pciback/xenbus.c
@@ -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 @@ out:

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;
}

--
1.7.4.1


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