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 moves device addition is_added bit to separate private flag
variable and use different atomic functions to set, clear and
retrieve device addition state. As is_added shares different
memory location so race condition is avoided.
Signed-off-by: Hari Vyas <hari.vyas@xxxxxxxxxxxx>
---
drivers/pci/bus.c | 6 +++---
drivers/pci/pci.c | 1 +
drivers/pci/pci.h | 18 ++++++++++++++++++
drivers/pci/probe.c | 4 ++--
drivers/pci/remove.c | 5 +++--
include/linux/pci.h | 1 -
6 files changed, 27 insertions(+), 8 deletions(-)
diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
index 35b7fc8..8674019 100644
--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -330,7 +330,7 @@ void pci_bus_add_device(struct pci_dev *dev)
return;
}
- dev->is_added = 1;
+ pci_dev_set_added(dev, NULL);
}
EXPORT_SYMBOL_GPL(pci_bus_add_device);
@@ -347,14 +347,14 @@ void pci_bus_add_devices(const struct pci_bus *bus)
list_for_each_entry(dev, &bus->devices, bus_list) {
/* Skip already-added devices */
- if (dev->is_added)
+ if (pci_dev_is_added(dev))
continue;
pci_bus_add_device(dev);
}
list_for_each_entry(dev, &bus->devices, bus_list) {
/* Skip if device attach failed */
- if (!dev->is_added)
+ if (!pci_dev_is_added(dev))
continue;
child = dev->subordinate;
if (child)
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 97acba7..baefd55 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3675,6 +3675,7 @@ static void __pci_set_master(struct pci_dev *dev, bool enable)
enable ? "enabling" : "disabling");
pci_write_config_word(dev, PCI_COMMAND, cmd);
}
+
dev->is_busmaster = enable;
}
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index c358e7a0..c924a4c 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -288,6 +288,7 @@ struct pci_sriov {
/* pci_dev priv_flags */
#define PCI_DEV_DISCONNECTED 0
+#define PCI_DEV_ADDED 1
static inline int pci_dev_set_disconnected(struct pci_dev *dev, void *unused)
{
@@ -300,6 +301,23 @@ static inline bool pci_dev_is_disconnected(const struct pci_dev *dev)
return test_bit(PCI_DEV_DISCONNECTED, &dev->priv_flags);
}
+static inline int pci_dev_set_added(struct pci_dev *dev, void *unused)
+{
+ set_bit(PCI_DEV_ADDED, &dev->priv_flags);
+ return 0;
+}
+
+static inline int pci_dev_clear_added(struct pci_dev *dev, void *unused)
+{
+ clear_bit(PCI_DEV_ADDED, &dev->priv_flags);
+ return 0;
+}
+
+static inline bool pci_dev_is_added(const struct pci_dev *dev)
+{
+ return test_bit(PCI_DEV_ADDED, &dev->priv_flags);
+}
+
#ifdef CONFIG_PCI_ATS
void pci_restore_ats_state(struct pci_dev *dev);
#else
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ac876e3..611adcd 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2433,13 +2433,13 @@ int pci_scan_slot(struct pci_bus *bus, int devfn)
dev = pci_scan_single_device(bus, devfn);
if (!dev)
return 0;
- if (!dev->is_added)
+ if (!pci_dev_is_added(dev))
nr++;
for (fn = next_fn(bus, dev, 0); fn > 0; fn = next_fn(bus, dev, fn)) {
dev = pci_scan_single_device(bus, devfn + fn);
if (dev) {
- if (!dev->is_added)
+ if (!pci_dev_is_added(dev))
nr++;
dev->multifunction = 1;
}
diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
index 6f072ea..a272cdc 100644
--- a/drivers/pci/remove.c
+++ b/drivers/pci/remove.c
@@ -19,11 +19,12 @@ static void pci_stop_dev(struct pci_dev *dev)
{
pci_pme_active(dev, false);
- if (dev->is_added) {
+ if (pci_dev_is_added(dev)) {
device_release_driver(&dev->dev);
pci_proc_detach_device(dev);
pci_remove_sysfs_dev_files(dev);
- dev->is_added = 0;
+
+ pci_dev_clear_added(dev, NULL);
}
if (dev->bus->self)
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 340029b..506125b 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -368,7 +368,6 @@ struct pci_dev {
unsigned int transparent:1; /* Subtractive decode bridge */
unsigned int multifunction:1; /* Multi-function device */
- unsigned int is_added:1;
unsigned int is_busmaster:1; /* Is busmaster */
unsigned int no_msi:1; /* May not use MSI */
unsigned int no_64bit_msi:1; /* May only use 32-bit MSIs */
--
1.9.1
