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 <jiang.liu@xxxxxxxxxx> Reported-by: Gu Zheng <guz.fnst@xxxxxxxxxxxxxx> Cc: linux-pci@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx --- 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 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
