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pciehp: fix a race between pciehp and removing operations by sysfs
测试补丁：
diff --git a/drivers/pci/hotplug/pciehp_pci.c b/drivers/pci/hotplug/pciehp_pci.c
index d17f3bf36f709..8fa086410989b 100644
--- a/drivers/pci/hotplug/pciehp_pci.c
+++ b/drivers/pci/hotplug/pciehp_pci.c
@@ -87,7 +87,7 @@ void pciehp_unconfigure_device(struct controller *ctrl, bool presence)
struct pci_bus *parent = ctrl->pcie->port->subordinate;
u16 command;
- ctrl_dbg(ctrl, "%s: domain:bus:dev = %04x:%02x:00\n",
+ ctrl_info(ctrl, "%s: domain:bus:dev = %04x:%02x:00\n",
__func__, pci_domain_nr(parent), parent->number);
if (!presence)
diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
index 95dec03d9f2a9..d511b2d321547 100644
--- a/drivers/pci/remove.c
+++ b/drivers/pci/remove.c
@@ -2,6 +2,7 @@
#include <linux/pci.h>
#include <linux/module.h>
#include "pci.h"
+#include <linux/delay.h>
static void pci_free_resources(struct pci_dev *dev)
{
@@ -121,6 +122,9 @@ EXPORT_SYMBOL(pci_stop_and_remove_bus_device);
void pci_stop_and_remove_bus_device_locked(struct pci_dev *dev)
{
pci_lock_rescan_remove();
+ pr_info("before mdelay\n");
+ mdelay(9000);
+ pr_info("after mdelay\n");
pci_stop_and_remove_bus_device(dev);
pci_unlock_rescan_remove();
}
测试方法：先删除这个设备，再起一个窗口通过hotplug移除这个设备
config:
EXT4 = y
CONFIG_VIRTIO=y
CONFIG_VIRTIO_PCI=y
CONFIG_VIRTIO_BLK=y
CONFIG_VIRTIO_NET=y
测试结果：
修复前:
root@syzkaller:~# echo 1 > /sys/bus/pci/devices/0000\:00\:02.0/remove
[ 154.822003][ T342] before mdelay
[ 157.681556][ T160] pcieport 0000:02:00.0: pciehp: Slot(0-1): Attention button pressed
[ 157.682301][ T160] pcieport 0000:02:00.0: pciehp: Slot(0-1): Powering off due to button press
[ 163.822881][ T342] after mdelay
[ 163.823292][ T160] pcieport 0000:02:00.0: pciehp: pciehp_unconfigure_device: domain:bus:dev = 0000:03:00
[ 363.527352][ T84] INFO: task irq/54-pciehp:160 blocked for more than 120 seconds.
[ 363.531457][ T84] Not tainted 5.10.0+ #13
[ 363.533969][ T84] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 363.538592][ T84] task:irq/54-pciehp state:D stack: 0 pid: 160 ppid: 2 flags:0x00000028
[ 363.543856][ T84] Call trace:
[ 363.545532][ T84] __switch_to+0xf4/0x160
[ 363.547794][ T84] __schedule+0x2f8/0x858
[ 363.550018][ T84] schedule+0x50/0xe0
[ 363.552103][ T84] schedule_preempt_disabled+0x18/0x28
[ 363.554947][ T84] __mutex_lock.isra.1+0x210/0x5a0
[ 363.557687][ T84] __mutex_lock_slowpath+0x1c/0x28
[ 363.560341][ T84] mutex_lock+0x4c/0x68
[ 363.562576][ T84] pci_lock_rescan_remove+0x24/0x30
[ 363.565344][ T84] pciehp_unconfigure_device+0x80/0x120
[ 363.568322][ T84] pciehp_disable_slot+0x78/0x150
[ 363.570970][ T84] pciehp_handle_disable_request+0x54/0x78
[ 363.574136][ T84] pciehp_ist+0x224/0x270
[ 363.576411][ T84] irq_thread_fn+0x34/0xa8
[ 363.578731][ T84] irq_thread+0x140/0x258
[ 363.581086][ T84] kthread+0x130/0x138
[ 363.583154][ T84] ret_from_fork+0x10/0x18
[ 363.585502][ T84] INFO: task bash:342 blocked for more than 120 seconds.
[ 363.589290][ T84] Not tainted 5.10.0+ #13
[ 363.591900][ T84] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 363.596486][ T84] task:bash state:D stack: 0 pid: 342 ppid: 287 flags:0x00000008
[ 363.601357][ T84] Call trace:
[ 363.603085][ T84] __switch_to+0xf4/0x160
[ 363.605355][ T84] __schedule+0x2f8/0x858
[ 363.607648][ T84] schedule+0x50/0xe0
[ 363.609787][ T84] schedule_timeout+0x27c/0x308
[ 363.612338][ T84] wait_for_common+0x190/0x230
[ 363.614844][ T84] wait_for_completion+0x20/0x30
[ 363.617451][ T84] kthread_stop+0x80/0x208
[ 363.619808][ T84] __free_irq+0x1cc/0x430
[ 363.622077][ T84] free_irq+0x3c/0x88
[ 363.624172][ T84] pcie_shutdown_notification+0x48/0x88
[ 363.627109][ T84] pciehp_remove+0x30/0x58
[ 363.629495][ T84] pcie_port_remove_service+0x40/0x68
[ 363.632369][ T84] device_release_driver_internal+0x118/0x1f0
[ 363.635586][ T84] device_release_driver+0x20/0x30
[ 363.638272][ T84] bus_remove_device+0xdc/0x168
[ 363.640838][ T84] device_del+0x174/0x3e8
[ 363.643097][ T84] device_unregister+0x28/0x80
[ 363.645727][ T84] remove_iter+0x34/0x48
[ 363.647968][ T84] device_for_each_child+0x68/0xb0
[ 363.650657][ T84] pcie_port_device_remove+0x30/0x50
[ 363.653535][ T84] pcie_portdrv_remove+0x30/0x90
[ 363.656189][ T84] pci_device_remove+0x48/0xf0
[ 363.658683][ T84] device_release_driver_internal+0x118/0x1f0
[ 363.661971][ T84] device_release_driver+0x20/0x30
[ 363.664674][ T84] pci_stop_bus_device+0x8c/0xe8
[ 363.667236][ T84] pci_stop_bus_device+0x54/0xe8
[ 363.669890][ T84] pci_stop_bus_device+0x40/0xe8
[ 363.672457][ T84] pci_stop_and_remove_bus_device_locked+0x64/0xa0
[ 363.675918][ T84] remove_store+0x98/0xa8
[ 363.678214][ T84] dev_attr_store+0x20/0x38
[ 363.680641][ T84] sysfs_kf_write+0x4c/0x60
[ 363.682986][ T84] kernfs_fop_write_iter+0x140/0x1d0
[ 363.685877][ T84] new_sync_write+0x108/0x190
[ 363.688438][ T84] vfs_write+0x224/0x2b0
[ 363.690699][ T84] ksys_write+0x70/0xf8
[ 363.692924][ T84] __arm64_sys_write+0x24/0x30
[ 363.695437][ T84] el0_svc_common.constprop.0+0xb8/0x208
[ 363.698439][ T84] do_el0_svc+0x2c/0x98
[ 363.700627][ T84] el0_svc+0x20/0x30
[ 363.702637][ T84] el0_sync_handler+0x90/0xb8
[ 363.705109][ T84] el0_sync+0x160/0x180
[root@10 qemu2]# telnet localhost 7011
Trying ::1...
Connected to localhost.
Escape character is '^]'.
QEMU 4.1.0 monitor - type 'help' for more information
(qemu) device_del upstream2
修复后：
root@syzkaller:~# echo 1 > /sys/bus/pci/devices/0000\:00\:02.0/remove
[ 123.446512][ T341] before mdelay
[ 125.875444][ T160] pcieport 0000:02:00.0: pciehp: Slot(0-1): Attention button pressed
[ 125.876160][ T160] pcieport 0000:02:00.0: pciehp: Slot(0-1): Slot operation failed because a remove or rescan operation is under processing, please try later!
[ 132.447467][ T341] after mdelay
[ 132.459178][ T341] pci_bus 0000:05: busn_res: [bus 05] is released
[ 132.460145][ T341] pci_bus 0000:06: busn_res: [bus 06] is released
[ 132.461014][ T341] pci_bus 0000:04: busn_res: [bus 04-06] is released
[ 132.461909][ T341] pci_bus 0000:03: busn_res: [bus 03-06] is released
[ 132.464064][ T341] pci_bus 0000:07: busn_res: [bus 07] is released
[ 132.465044][ T341] pci_bus 0000:02: busn_res: [bus 02-07] is released
[ 132.465936][ T341] pci_bus 0000:01: busn_res: [bus 01-07] is released
[root@10 qemu2]# telnet localhost 7011
Trying ::1...
Connected to localhost.
Escape character is '^]'.
QEMU 4.1.0 monitor - type 'help' for more information
(qemu) device_del upstream2
pciehp: do not wake up irq_thread for sysfs operation
OLK-5.10已经有如下修复补丁：
157c1062fcd8 PCI: pciehp: Avoid returning prematurely from sysfs requests
diff --git a/drivers/pci/hotplug/pciehp.h b/drivers/pci/hotplug/pciehp.h
index 654c972b8ea0c..882ce82c46990 100644
--- a/drivers/pci/hotplug/pciehp.h
+++ b/drivers/pci/hotplug/pciehp.h
@@ -72,6 +72,7 @@ extern int pciehp_poll_time;
* @reset_lock: prevents access to the Data Link Layer Link Active bit in the
* Link Status register and to the Presence Detect State bit in the Slot
* Status register during a slot reset which may cause them to flap
+ * @ist_running: flag to keep user request waiting while IRQ thread is running
* @request_result: result of last user request submitted to the IRQ thread
* @requester: wait queue to wake up on completion of user request,
* used for synchronous slot enable/disable request via sysfs
@@ -101,6 +102,7 @@ struct controller {
struct hotplug_slot hotplug_slot; /* hotplug core interface */
struct rw_semaphore reset_lock;
+ unsigned int ist_running;
int request_result;
wait_queue_head_t requester;
};
diff --git a/drivers/pci/hotplug/pciehp_ctrl.c b/drivers/pci/hotplug/pciehp_ctrl.c
index 21af7b16d7a4f..dd8e4a5fb2826 100644
--- a/drivers/pci/hotplug/pciehp_ctrl.c
+++ b/drivers/pci/hotplug/pciehp_ctrl.c
@@ -375,7 +375,8 @@ int pciehp_sysfs_enable_slot(struct hotplug_slot *hotplug_slot)
ctrl->request_result = -ENODEV;
pciehp_request(ctrl, PCI_EXP_SLTSTA_PDC);
wait_event(ctrl->requester,
- !atomic_read(&ctrl->pending_events));
+ !atomic_read(&ctrl->pending_events) &&
+ !ctrl->ist_running);
return ctrl->request_result;
case POWERON_STATE:
ctrl_info(ctrl, "Slot(%s): Already in powering on state\n",
@@ -408,7 +409,8 @@ int pciehp_sysfs_disable_slot(struct hotplug_slot *hotplug_slot)
mutex_unlock(&ctrl->state_lock);
pciehp_request(ctrl, DISABLE_SLOT);
wait_event(ctrl->requester,
- !atomic_read(&ctrl->pending_events));
+ !atomic_read(&ctrl->pending_events) &&
+ !ctrl->ist_running);
return ctrl->request_result;
case POWEROFF_STATE:
ctrl_info(ctrl, "Slot(%s): Already in powering off state\n",
diff --git a/drivers/pci/hotplug/pciehp_hpc.c b/drivers/pci/hotplug/pciehp_hpc.c
index 1a522c1c41772..86d97f3112f02 100644
--- a/drivers/pci/hotplug/pciehp_hpc.c
+++ b/drivers/pci/hotplug/pciehp_hpc.c
@@ -583,6 +583,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
irqreturn_t ret;
u32 events;
+ ctrl->ist_running = true;
pci_config_pm_runtime_get(pdev);
/* rerun pciehp_isr() if the port was inaccessible on interrupt */
@@ -629,6 +630,7 @@ static irqreturn_t pciehp_ist(int irq, void *dev_id)
up_read(&ctrl->reset_lock);
pci_config_pm_runtime_put(pdev);
+ ctrl->ist_running = false;
wake_up(&ctrl->requester);
return IRQ_HANDLED;
}
因此，只合入pciehp: do not wake up irq_thread for sysfs operation与Fixes: 764cafd9875e ("pciehp: fix a race between pciehp and removing operations by sysfs")有关的部分。
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