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Subject[PATCH 1/5] pci: Introduce __pci_reset_function_locked to be used when holding device_lock.
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The use case of this is when a driver wants to call FLR when a device
is attached to it using the SysFS "bind" or "unbind" functionality.

The call chain when a user does "bind" looks as so:

echo "0000:01.07.0" > /sys/bus/pci/drivers/XXXX/bind
and ends up calling:
driver_bind:
device_lock(dev); <=== TAKES LOCK
XXXX_probe:
.. pci_enable_device()
...__pci_reset_function(), which calls
pci_dev_reset(dev, 0):
if (!0) {
device_lock(dev) <==== DEADLOCK
The __pci_reset_function_locked function allows the the drivers
'probe' function to call the "pci_reset_function" while still holding
the driver mutex lock.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
drivers/pci/pci.c | 25 +++++++++++++++++++++++++
include/linux/pci.h | 1 +
2 files changed, 26 insertions(+), 0 deletions(-)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 6d4a531..f9a2a0d 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3020,6 +3020,31 @@ int __pci_reset_function(struct pci_dev *dev)
EXPORT_SYMBOL_GPL(__pci_reset_function);

/**
+ * __pci_reset_function_locked - reset a PCI device function while holding
+ * the @dev mutex lock.
+ * @dev: PCI device to reset
+ *
+ * Some devices allow an individual function to be reset without affecting
+ * other functions in the same device. The PCI device must be responsive
+ * to PCI config space in order to use this function.
+ *
+ * The device function is presumed to be unused and the caller is holding
+ * the device mutex lock when this function is called.
+ * Resetting the device will make the contents of PCI configuration space
+ * random, so any caller of this must be prepared to reinitialise the
+ * device including MSI, bus mastering, BARs, decoding IO and memory spaces,
+ * etc.
+ *
+ * Returns 0 if the device function was successfully reset or negative if the
+ * device doesn't support resetting a single function.
+ */
+int __pci_reset_function_locked(struct pci_dev *dev)
+{
+ return pci_dev_reset(dev, 1);
+}
+EXPORT_SYMBOL_GPL(__pci_reset_function_locked);
+
+/**
* pci_probe_reset_function - check whether the device can be safely reset
* @dev: PCI device to reset
*
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 7cda65b..af5ee43 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -814,6 +814,7 @@ int pcie_set_readrq(struct pci_dev *dev, int rq);
int pcie_get_mps(struct pci_dev *dev);
int pcie_set_mps(struct pci_dev *dev, int mps);
int __pci_reset_function(struct pci_dev *dev);
+int __pci_reset_function_locked(struct pci_dev *dev);
int pci_reset_function(struct pci_dev *dev);
void pci_update_resource(struct pci_dev *dev, int resno);
int __must_check pci_assign_resource(struct pci_dev *dev, int i);
--
1.7.7.4


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