When a pci device is detected, a variable is_added is set to
1 in pci device structure and proc, sys entries are created.
When a pci device is removed, first is_added is checked for one
and then device is detached with clearing of proc and sys
entries and at end, is_added is set to 0.
is_added and is_busmaster are bit fields in pci_dev structure
sharing same memory location.
A strange issue was observed with multiple times removal and
rescan of a pcie nvme device using sysfs commands where is_added
flag was observed as zero instead of one while removing device
and proc,sys entries are not cleared. This causes issue in
later device addition with warning message "proc_dir_entry"
already registered.
Debugging revealed a race condition between pcie core driver
enabling is_added bit(pci_bus_add_device()) and nvme driver
reset work-queue enabling is_busmaster bit (by pci_set_master()).
As both fields are not handled in atomic manner and that clears
is_added bit.
Fix protects is_added and is_busmaster bits updation by a spin
locking mechanism.
Signed-off-by: Hari Vyas <hari.vyas@xxxxxxxxxxxx>
Reviewed-by: Ray Jui <ray.jui@xxxxxxxxxxxx>
---
drivers/pci/bus.c | 3 +++
drivers/pci/pci-driver.c | 2 ++
drivers/pci/pci.c | 7 +++++++
drivers/pci/remove.c | 5 +++++
include/linux/pci.h | 1 +
5 files changed, 18 insertions(+)
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 35b7fc8..61d389d 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -310,6 +310,7 @@ void __weak pcibios_bus_add_device(struct pci_dev *pdev) { }
void pci_bus_add_device(struct pci_dev *dev)
{
int retval;
+ unsigned long flags;
/*
* Can not put in pci_device_add yet because resources
@@ -330,7 +331,9 @@ void pci_bus_add_device(struct pci_dev *dev)
return;
}
+ spin_lock_irqsave(&dev->lock, flags);
dev->is_added = 1;
+ spin_unlock_irqrestore(&dev->lock, flags);
}
EXPORT_SYMBOL_GPL(pci_bus_add_device);
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index c125d53..547bcd7 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -123,6 +123,8 @@ static ssize_t new_id_store(struct device_driver *driver, const char *buf,
pdev->subsystem_device = subdevice;
pdev->class = class;
+ spin_lock_init(&pdev->lock);
+
if (pci_match_id(pdrv->id_table, pdev))
retval = -EEXIST;
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 97acba7..bcb1f96 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1649,6 +1649,7 @@ void pci_disable_enabled_device(struct pci_dev *dev)
void pci_disable_device(struct pci_dev *dev)
{
struct pci_devres *dr;
+ unsigned long flags;
dr = find_pci_dr(dev);
if (dr)
@@ -1662,7 +1663,9 @@ void pci_disable_device(struct pci_dev *dev)
do_pci_disable_device(dev);
+ spin_lock_irqsave(&dev->lock, flags);
dev->is_busmaster = 0;
+ spin_unlock_irqrestore(&dev->lock, flags);
}
EXPORT_SYMBOL(pci_disable_device);
@@ -3664,6 +3667,7 @@ void __iomem *devm_pci_remap_cfg_resource(struct device *dev,
static void __pci_set_master(struct pci_dev *dev, bool enable)
{
u16 old_cmd, cmd;
+ unsigned long flags;
pci_read_config_word(dev, PCI_COMMAND, &old_cmd);
if (enable)
@@ -3675,7 +3679,10 @@ static void __pci_set_master(struct pci_dev *dev, bool enable)
enable ? "enabling" : "disabling");
pci_write_config_word(dev, PCI_COMMAND, cmd);
}
+
+ spin_lock_irqsave(&dev->lock, flags);
dev->is_busmaster = enable;
+ spin_unlock_irqrestore(&dev->lock, flags);
}
/**
diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
index 6f072ea..ff57bd6 100644
--- a/drivers/pci/remove.c
+++ b/drivers/pci/remove.c
@@ -17,13 +17,18 @@ static void pci_free_resources(struct pci_dev *dev)
static void pci_stop_dev(struct pci_dev *dev)
{
+ unsigned long flags;
+
pci_pme_active(dev, false);
if (dev->is_added) {
device_release_driver(&dev->dev);
pci_proc_detach_device(dev);
pci_remove_sysfs_dev_files(dev);
+
+ spin_lock_irqsave(&dev->lock, flags);
dev->is_added = 0;
+ spin_unlock_irqrestore(&dev->lock, flags);
}
if (dev->bus->self)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 340029b..6940825 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -365,6 +365,7 @@ struct pci_dev {
bool match_driver; /* Skip attaching driver */
+ spinlock_t lock; /* Protect is_added and is_busmaster */
unsigned int transparent:1; /* Subtractive decode bridge */
unsigned int multifunction:1; /* Multi-function device */
--
1.9.1
