@@ -1672,6 +1672,8 @@ static void pci_enable_bridge(struct pci_dev *dev)
struct pci_dev *bridge;
int retval;
+ mutex_lock(&dev->enable_mutex);
+
bridge = pci_upstream_bridge(dev);
if (bridge)
pci_enable_bridge(bridge);
@@ -1679,6 +1681,7 @@ static void pci_enable_bridge(struct pci_dev *dev)
if (pci_is_enabled(dev)) {
if (!dev->is_busmaster)
pci_set_master(dev);
+ mutex_unlock(&dev->enable_mutex);
return;
}
@@ -1687,11 +1690,14 @@ static void pci_enable_bridge(struct pci_dev *dev)
pci_err(dev, "Error enabling bridge (%d), continuing\n",
retval);
pci_set_master(dev);
+ mutex_unlock(&dev->enable_mutex);
}
static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
{
struct pci_dev *bridge;
+ /* Enable-locking of bridges is performed within the pci_enable_bridge() */
+ bool need_lock = !dev->subordinate;
int err;
int i, bars = 0;
@@ -1707,8 +1713,13 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
}
- if (atomic_inc_return(&dev->enable_cnt) > 1)
+ if (need_lock)
+ mutex_lock(&dev->enable_mutex);
+ if (pci_is_enabled(dev)) {
+ if (need_lock)
+ mutex_unlock(&dev->enable_mutex);
return 0; /* already enabled */
+ }
bridge = pci_upstream_bridge(dev);
if (bridge)
@@ -1723,8 +1734,10 @@ static int pci_enable_device_flags(struct pci_dev *dev, unsigned long flags)
bars |= (1 << i);
err = do_pci_enable_device(dev, bars);
- if (err < 0)
- atomic_dec(&dev->enable_cnt);
+ if (err >= 0)
+ atomic_inc(&dev->enable_cnt);
+ if (need_lock)
+ mutex_unlock(&dev->enable_mutex);
return err;
}
@@ -1968,15 +1981,20 @@ void pci_disable_device(struct pci_dev *dev)
if (dr)
dr->enabled = 0;
+ mutex_lock(&dev->enable_mutex);
dev_WARN_ONCE(&dev->dev, atomic_read(&dev->enable_cnt) <= 0,
"disabling already-disabled device");
- if (atomic_dec_return(&dev->enable_cnt) != 0)
+ if (atomic_dec_return(&dev->enable_cnt) != 0) {
+ mutex_unlock(&dev->enable_mutex);
return;
+ }
do_pci_disable_device(dev);
dev->is_busmaster = 0;
+
+ mutex_unlock(&dev->enable_mutex);
}
EXPORT_SYMBOL(pci_disable_device);
@@ -2169,6 +2169,7 @@ struct pci_dev *pci_alloc_dev(struct pci_bus *bus)
INIT_LIST_HEAD(&dev->bus_list);
dev->dev.type = &pci_dev_type;
dev->bus = pci_bus_get(bus);
+ mutex_init(&dev->enable_mutex);
return dev;
}
@@ -424,6 +424,7 @@ struct pci_dev {
unsigned int no_vf_scan:1; /* Don't scan for VFs after IOV enablement */
pci_dev_flags_t dev_flags;
atomic_t enable_cnt; /* pci_enable_device has been called */
+ struct mutex enable_mutex;
u32 saved_config_space[16]; /* Config space saved at suspend time */
struct hlist_head saved_cap_space;
This is a yet another approach to fix an old [1-2] concurrency issue, when: - two or more devices are being hot-added into a bridge which was initially empty; - a bridge with two or more devices is being hot-added; - during boot, if BIOS/bootloader/firmware doesn't pre-enable bridges. The problem is that a bridge is reported as enabled before the MEM/IO bits are actually written to the PCI_COMMAND register, so another driver thread starts memory requests through the not-yet-enabled bridge: CPU0 CPU1 pci_enable_device_mem() pci_enable_device_mem() pci_enable_bridge() pci_enable_bridge() pci_is_enabled() return false; atomic_inc_return(enable_cnt) Start actual enabling the bridge ... pci_is_enabled() ... return true; ... Start memory requests <-- FAIL ... Set the PCI_COMMAND_MEMORY bit <-- Must wait for this Protect the pci_enable/disable_device() and pci_enable_bridge(), which is similar to the previous solution from commit 40f11adc7cd9 ("PCI: Avoid race while enabling upstream bridges"), but adding a per-device mutexes and preventing the dev->enable_cnt from from incrementing early. CC: Srinath Mannam <srinath.mannam@broadcom.com> CC: Marta Rybczynska <mrybczyn@kalray.eu> Signed-off-by: Sergei Miroshnichenko <s.miroshnichenko@yadro.com> [1] https://lore.kernel.org/linux-pci/1501858648-22228-1-git-send-email-srinath.mannam@broadcom.com/T/#u [RFC PATCH v3] pci: Concurrency issue during pci enable bridge [2] https://lore.kernel.org/linux-pci/744877924.5841545.1521630049567.JavaMail.zimbra@kalray.eu/T/#u [RFC PATCH] nvme: avoid race-conditions when enabling devices --- drivers/pci/pci.c | 26 ++++++++++++++++++++++---- drivers/pci/probe.c | 1 + include/linux/pci.h | 1 + 3 files changed, 24 insertions(+), 4 deletions(-)