Use PCI bus lock to serialize hotplug operations triggered by pci-sysfs,
and remove the redundant local mutex pci_remove_rescan_mutex.
This also fixes the bug reported by Gu Zheng as:
echo -n 1 > /sys/bus/pci/devices/0000\:10\:00.0/remove ; echo -n 1 >
/sys/bus/pci/devices/0000\:1a\:01.0/remove
will cause kernel crash as bus get freed.
[ 418.946462] CPU 4
[ 418.968377] Pid: 512, comm: kworker/u:2 Tainted: G W 3.8.0 #2
FUJITSU-SV PRIMEQUEST 1800E/SB
[ 419.081763] RIP: 0010:[<ffffffff8137972e>] [<ffffffff8137972e>]
pci_bus_read_config_word+0x5e/0x90
[ 420.494137] Call Trace:
[ 420.523326] [<ffffffff813851ef>] ? remove_callback+0x1f/0x40
[ 420.591984] [<ffffffff8138044b>] pci_pme_active+0x4b/0x1c0
[ 420.658545] [<ffffffff8137d8e7>] pci_stop_bus_device+0x57/0xb0
[ 420.729259] [<ffffffff8137dab6>] pci_stop_and_remove_bus_device+0x16/0x30
[ 420.811392] [<ffffffff813851fb>] remove_callback+0x2b/0x40
[ 420.877955] [<ffffffff81257a56>] sysfs_schedule_callback_work+0x26/0x70
https://bugzilla.kernel.org/show_bug.cgi?id=54411
Signed-off-by: Jiang Liu <[email protected]>
Reported-by: Gu Zheng <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
drivers/pci/pci-sysfs.c | 52 ++++++++++++++++++++++++++++++++-----------------
1 file changed, 34 insertions(+), 18 deletions(-)
diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index fcc4bb2..91ff11e 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -284,7 +284,6 @@ msi_bus_store(struct device *dev, struct device_attribute
*attr,
return count;
}
-static DEFINE_MUTEX(pci_remove_rescan_mutex);
static ssize_t bus_rescan_store(struct bus_type *bus, const char *buf,
size_t count)
{
@@ -293,13 +292,15 @@ static ssize_t bus_rescan_store(struct bus_type *bus,
const char *buf,
if (strict_strtoul(buf, 0, &val) < 0)
return -EINVAL;
+ if (!val)
+ return count;
- if (val) {
- mutex_lock(&pci_remove_rescan_mutex);
- for_each_pci_root_bus(b)
+ for_each_pci_root_bus(b)
+ if (pci_bus_lock(b, PCI_BUS_STATE_STOPPING - 1, true) == 0) {
pci_rescan_bus(b);
- mutex_unlock(&pci_remove_rescan_mutex);
- }
+ pci_bus_unlock(b, true);
+ }
+
return count;
}
@@ -312,27 +313,41 @@ static ssize_t
dev_rescan_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
{
+ int ret;
unsigned long val;
struct pci_dev *pdev = to_pci_dev(dev);
if (strict_strtoul(buf, 0, &val) < 0)
return -EINVAL;
+ if (!val)
+ return count;
+
+ do {
+ ret = pci_bus_lock_timeout(pdev->bus,
+ PCI_BUS_STATE_STOPPING - 1, true, HZ);
+ if (ret == 0) {
+ pci_rescan_bus(pdev->bus);
+ pci_bus_unlock(pdev->bus, true);
+ break;
+ }
+ /*
+ * Prevent a deadlock scenario that thread A waits for
+ * all sysfs files to be released while holding PCI bus
+ * locks, and Thread B tries to acquire PCI bus locks
+ * in a sysfs handler. These checks break the deadlock
+ * condition.
+ */
+ if (pci_dev_get_state(pdev) >= PCI_DEV_STATE_STOPPING ||
+ pci_bus_get_state(pdev->bus) >= PCI_BUS_STATE_STOPPING)
+ return -EBUSY;
+ } while (true);
- if (val) {
- mutex_lock(&pci_remove_rescan_mutex);
- pci_rescan_bus(pdev->bus);
- mutex_unlock(&pci_remove_rescan_mutex);
- }
return count;
}
static void remove_callback(struct device *dev)
{
- struct pci_dev *pdev = to_pci_dev(dev);
-
- mutex_lock(&pci_remove_rescan_mutex);
- pci_stop_and_remove_bus_device(pdev);
- mutex_unlock(&pci_remove_rescan_mutex);
+ pci_stop_and_remove_device(to_pci_dev(dev));
}
static ssize_t
@@ -366,12 +381,13 @@ dev_bus_rescan_store(struct device *dev, struct
device_attribute *attr,
return -EINVAL;
if (val) {
- mutex_lock(&pci_remove_rescan_mutex);
+ if (pci_bus_lock(bus, PCI_BUS_STATE_STOPPING - 1, true) < 0)
+ return -EBUSY;
if (!pci_is_root_bus(bus) && list_empty(&bus->devices))
pci_rescan_bus_bridge_resize(bus->self);
else
pci_rescan_bus(bus);
- mutex_unlock(&pci_remove_rescan_mutex);
+ pci_bus_unlock(bus, true);
}
return count;
}
--
1.8.1.2
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