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SubjectRe: [PATCH] xen/pciback: Use mutexes when working with Xenbus state transitions.
>>> On 16.09.11 at 21:06, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:

> 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

This is only the direct conversion of existing spinlock accesses in
xenbus.c. However, in the course of converting from the legacy
implementation you stripped a couple more (in xen_pcibk_attach(),
xen_pcibk_reconfigure(), and xen_pcibk_setup_backend()), and
those should now get re-added imo.

Jan

> 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 | 16 +++++-----------
> 2 files changed, 6 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/xen/xen-pciback/pciback.h
> b/drivers/xen/xen-pciback/pciback.h
> index a0e131a..c3af628 100644
> --- a/drivers/xen/xen-pciback/pciback.h
> +++ b/drivers/xen/xen-pciback/pciback.h
> @@ -27,7 +27,7 @@ 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 978d2c6..c057d67 100644
> --- a/drivers/xen/xen-pciback/xenbus.c
> +++ b/drivers/xen/xen-pciback/xenbus.c
> @@ -44,7 +44,7 @@ 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;
> @@ -62,14 +62,13 @@ 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 */
> @@ -77,13 +76,11 @@ 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)
> @@ -120,9 +117,8 @@ static int xen_pcibk_do_attach(struct xen_pcibk_device
> *pdev, int gnt_ref,
> goto out;
> }
>
> - spin_lock(&pdev->dev_lock);
> + mutex_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,
> @@ -132,14 +128,12 @@ 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");
> out:
> + mutex_unlock(&pdev->dev_lock);
> return err;
> }
>





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