[PATCH 6.6 158/158] PCI/ASPM: Fix deadlock when enabling ASPM

Greg Kroah-Hartman
2024-04-23T21:44:29Z

From: Johan Hovold <johan+linaro@kernel.org>

commit 1e560864159d002b453da42bd2c13a1805515a20 upstream.

A last minute revert in 6.7-final introduced a potential deadlock when
enabling ASPM during probe of Qualcomm PCIe controllers as reported by
lockdep:

============================================
WARNING: possible recursive locking detected
6.7.0 #40 Not tainted
--------------------------------------------
kworker/u16:5/90 is trying to acquire lock:
ffffacfa78ced000 (pci_bus_sem){++++}-{3:3}, at: pcie_aspm_pm_state_change+0x58/0xdc

but task is already holding lock:
ffffacfa78ced000 (pci_bus_sem){++++}-{3:3}, at: pci_walk_bus+0x34/0xbc

other info that might help us debug this:
Possible unsafe locking scenario:

CPU0
----
lock(pci_bus_sem);
lock(pci_bus_sem);

*** DEADLOCK ***

Call trace:
print_deadlock_bug+0x25c/0x348
__lock_acquire+0x10a4/0x2064
lock_acquire+0x1e8/0x318
down_read+0x60/0x184
pcie_aspm_pm_state_change+0x58/0xdc
pci_set_full_power_state+0xa8/0x114
pci_set_power_state+0xc4/0x120
qcom_pcie_enable_aspm+0x1c/0x3c [pcie_qcom]
pci_walk_bus+0x64/0xbc
qcom_pcie_host_post_init_2_7_0+0x28/0x34 [pcie_qcom]

The deadlock can easily be reproduced on machines like the Lenovo ThinkPad
X13s by adding a delay to increase the race window during asynchronous
probe where another thread can take a write lock.

Add a new pci_set_power_state_locked() and associated helper functions that
can be called with the PCI bus semaphore held to avoid taking the read lock
twice.

Link: https://lore.kernel.org/r/ZZu0qx2cmn7IwTyQ@hovoldconsulting.com
Link: https://lore.kernel.org/r/20240130100243.11011-1-johan+linaro@kernel.org
Fixes: f93e71aea6c6 ("Revert "PCI/ASPM: Remove pcie_aspm_pm_state_change()"")
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: <stable@vger.kernel.org> # 6.7
[bhelgaas: backported to v6.6.y, which contains 8cc22ba3f77c ("Revert
"PCI/ASPM: Remove pcie_aspm_pm_state_change()""), a backport of
f93e71aea6c6. This omits the drivers/pci/controller/dwc/pcie-qcom.c hunk
that updates qcom_pcie_enable_aspm(), which was added by 9f4f3dfad8cf
("PCI: qcom: Enable ASPM for platforms supporting 1.9.0 ops"), which is not
present in v6.6.28.]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/pci/bus.c | 49 +++++++++++++++++++-----------
drivers/pci/pci.c | 78 ++++++++++++++++++++++++++++++++----------------
drivers/pci/pci.h | 4 +-
drivers/pci/pcie/aspm.c | 13 +++++---
include/linux/pci.h | 5 +++
5 files changed, 100 insertions(+), 49 deletions(-)

--- a/drivers/pci/bus.c
+++ b/drivers/pci/bus.c
@@ -386,21 +386,8 @@ void pci_bus_add_devices(const struct pc
}
EXPORT_SYMBOL(pci_bus_add_devices);

-/** pci_walk_bus - walk devices on/under bus, calling callback.
- * @top bus whose devices should be walked
- * @cb callback to be called for each device found
- * @userdata arbitrary pointer to be passed to callback.
- *
- * Walk the given bus, including any bridged devices
- * on buses under this bus. Call the provided callback
- * on each device found.
- *
- * We check the return of @cb each time. If it returns anything
- * other than 0, we break out.
- *
- */
-void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
- void *userdata)
+static void __pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
+ void *userdata, bool locked)
{
struct pci_dev *dev;
struct pci_bus *bus;
@@ -408,7 +395,8 @@ void pci_walk_bus(struct pci_bus *top, i
int retval;

bus = top;
- down_read(&pci_bus_sem);
+ if (!locked)
+ down_read(&pci_bus_sem);
next = top->devices.next;
for (;;) {
if (next == &bus->devices) {
@@ -431,10 +419,37 @@ void pci_walk_bus(struct pci_bus *top, i
if (retval)
break;
}
- up_read(&pci_bus_sem);
+ if (!locked)
+ up_read(&pci_bus_sem);
+}
+
+/**
+ * pci_walk_bus - walk devices on/under bus, calling callback.
+ * @top: bus whose devices should be walked
+ * @cb: callback to be called for each device found
+ * @userdata: arbitrary pointer to be passed to callback
+ *
+ * Walk the given bus, including any bridged devices
+ * on buses under this bus. Call the provided callback
+ * on each device found.
+ *
+ * We check the return of @cb each time. If it returns anything
+ * other than 0, we break out.
+ */
+void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), void *userdata)
+{
+ __pci_walk_bus(top, cb, userdata, false);
}
EXPORT_SYMBOL_GPL(pci_walk_bus);

+void pci_walk_bus_locked(struct pci_bus *top, int (*cb)(struct pci_dev *, void *), void *userdata)
+{
+ lockdep_assert_held(&pci_bus_sem);
+
+ __pci_walk_bus(top, cb, userdata, true);
+}
+EXPORT_SYMBOL_GPL(pci_walk_bus_locked);
+
struct pci_bus *pci_bus_get(struct pci_bus *bus)
{
if (bus)
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1291,6 +1291,7 @@ end:
/**
* pci_set_full_power_state - Put a PCI device into D0 and update its state
* @dev: PCI device to power up
+ * @locked: whether pci_bus_sem is held
*
* Call pci_power_up() to put @dev into D0, read from its PCI_PM_CTRL register
* to confirm the state change, restore its BARs if they might be lost and
@@ -1300,7 +1301,7 @@ end:
* to D0, it is more efficient to use pci_power_up() directly instead of this
* function.
*/
-static int pci_set_full_power_state(struct pci_dev *dev)
+static int pci_set_full_power_state(struct pci_dev *dev, bool locked)
{
u16 pmcsr;
int ret;
@@ -1336,7 +1337,7 @@ static int pci_set_full_power_state(stru
}

if (dev->bus->self)
- pcie_aspm_pm_state_change(dev->bus->self);
+ pcie_aspm_pm_state_change(dev->bus->self, locked);

return 0;
}
@@ -1365,10 +1366,22 @@ void pci_bus_set_current_state(struct pc
pci_walk_bus(bus, __pci_dev_set_current_state, &state);
}

+static void __pci_bus_set_current_state(struct pci_bus *bus, pci_power_t state, bool locked)
+{
+ if (!bus)
+ return;
+
+ if (locked)
+ pci_walk_bus_locked(bus, __pci_dev_set_current_state, &state);
+ else
+ pci_walk_bus(bus, __pci_dev_set_current_state, &state);
+}
+
/**
* pci_set_low_power_state - Put a PCI device into a low-power state.
* @dev: PCI device to handle.
* @state: PCI power state (D1, D2, D3hot) to put the device into.
+ * @locked: whether pci_bus_sem is held
*
* Use the device's PCI_PM_CTRL register to put it into a low-power state.
*
@@ -1379,7 +1392,7 @@ void pci_bus_set_current_state(struct pc
* 0 if device already is in the requested state.
* 0 if device's power state has been successfully changed.
*/
-static int pci_set_low_power_state(struct pci_dev *dev, pci_power_t state)
+static int pci_set_low_power_state(struct pci_dev *dev, pci_power_t state, bool locked)
{
u16 pmcsr;

@@ -1433,29 +1446,12 @@ static int pci_set_low_power_state(struc
pci_power_name(state));

if (dev->bus->self)
- pcie_aspm_pm_state_change(dev->bus->self);
+ pcie_aspm_pm_state_change(dev->bus->self, locked);

return 0;
}

-/**
- * pci_set_power_state - Set the power state of a PCI device
- * @dev: PCI device to handle.
- * @state: PCI power state (D0, D1, D2, D3hot) to put the device into.
- *
- * Transition a device to a new power state, using the platform firmware and/or
- * the device's PCI PM registers.
- *
- * RETURN VALUE:
- * -EINVAL if the requested state is invalid.
- * -EIO if device does not support PCI PM or its PM capabilities register has a
- * wrong version, or device doesn't support the requested state.
- * 0 if the transition is to D1 or D2 but D1 and D2 are not supported.
- * 0 if device already is in the requested state.
- * 0 if the transition is to D3 but D3 is not supported.
- * 0 if device's power state has been successfully changed.
- */
-int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
+static int __pci_set_power_state(struct pci_dev *dev, pci_power_t state, bool locked)
{
int error;

@@ -1479,7 +1475,7 @@ int pci_set_power_state(struct pci_dev *
return 0;

if (state == PCI_D0)
- return pci_set_full_power_state(dev);
+ return pci_set_full_power_state(dev, locked);

/*
* This device is quirked not to be put into D3, so don't put it in
@@ -1493,16 +1489,16 @@ int pci_set_power_state(struct pci_dev *
* To put the device in D3cold, put it into D3hot in the native
* way, then put it into D3cold using platform ops.
*/
- error = pci_set_low_power_state(dev, PCI_D3hot);
+ error = pci_set_low_power_state(dev, PCI_D3hot, locked);

if (pci_platform_power_transition(dev, PCI_D3cold))
return error;

/* Powering off a bridge may power off the whole hierarchy */
if (dev->current_state == PCI_D3cold)
- pci_bus_set_current_state(dev->subordinate, PCI_D3cold);
+ __pci_bus_set_current_state(dev->subordinate, PCI_D3cold, locked);
} else {
- error = pci_set_low_power_state(dev, state);
+ error = pci_set_low_power_state(dev, state, locked);

if (pci_platform_power_transition(dev, state))
return error;
@@ -1510,8 +1506,38 @@ int pci_set_power_state(struct pci_dev *

return 0;
}
+
+/**
+ * pci_set_power_state - Set the power state of a PCI device
+ * @dev: PCI device to handle.
+ * @state: PCI power state (D0, D1, D2, D3hot) to put the device into.
+ *
+ * Transition a device to a new power state, using the platform firmware and/or
+ * the device's PCI PM registers.
+ *
+ * RETURN VALUE:
+ * -EINVAL if the requested state is invalid.
+ * -EIO if device does not support PCI PM or its PM capabilities register has a
+ * wrong version, or device doesn't support the requested state.
+ * 0 if the transition is to D1 or D2 but D1 and D2 are not supported.
+ * 0 if device already is in the requested state.
+ * 0 if the transition is to D3 but D3 is not supported.
+ * 0 if device's power state has been successfully changed.
+ */
+int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
+{
+ return __pci_set_power_state(dev, state, false);
+}
EXPORT_SYMBOL(pci_set_power_state);

+int pci_set_power_state_locked(struct pci_dev *dev, pci_power_t state)
+{
+ lockdep_assert_held(&pci_bus_sem);
+
+ return __pci_set_power_state(dev, state, true);
+}
+EXPORT_SYMBOL(pci_set_power_state_locked);
+
#define PCI_EXP_SAVE_REGS 7

static struct pci_cap_saved_state *_pci_find_saved_cap(struct pci_dev *pci_dev,
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -561,12 +561,12 @@ int pcie_retrain_link(struct pci_dev *pd
#ifdef CONFIG_PCIEASPM
void pcie_aspm_init_link_state(struct pci_dev *pdev);
void pcie_aspm_exit_link_state(struct pci_dev *pdev);
-void pcie_aspm_pm_state_change(struct pci_dev *pdev);
+void pcie_aspm_pm_state_change(struct pci_dev *pdev, bool locked);
void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
#else
static inline void pcie_aspm_init_link_state(struct pci_dev *pdev) { }
static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev) { }
-static inline void pcie_aspm_pm_state_change(struct pci_dev *pdev) { }
+static inline void pcie_aspm_pm_state_change(struct pci_dev *pdev, bool locked) { }
static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev) { }
#endif

--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -1001,8 +1001,11 @@ void pcie_aspm_exit_link_state(struct pc
up_read(&pci_bus_sem);
}

-/* @pdev: the root port or switch downstream port */
-void pcie_aspm_pm_state_change(struct pci_dev *pdev)
+/*
+ * @pdev: the root port or switch downstream port
+ * @locked: whether pci_bus_sem is held
+ */
+void pcie_aspm_pm_state_change(struct pci_dev *pdev, bool locked)
{
struct pcie_link_state *link = pdev->link_state;

@@ -1012,12 +1015,14 @@ void pcie_aspm_pm_state_change(struct pc
* Devices changed PM state, we should recheck if latency
* meets all functions' requirement
*/
- down_read(&pci_bus_sem);
+ if (!locked)
+ down_read(&pci_bus_sem);
mutex_lock(&aspm_lock);
pcie_update_aspm_capable(link->root);
pcie_config_aspm_path(link);
mutex_unlock(&aspm_lock);
- up_read(&pci_bus_sem);
+ if (!locked)
+ up_read(&pci_bus_sem);
}

void pcie_aspm_powersave_config_link(struct pci_dev *pdev)
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1391,6 +1391,7 @@ int pci_load_and_free_saved_state(struct
struct pci_saved_state **state);
int pci_platform_power_transition(struct pci_dev *dev, pci_power_t state);
int pci_set_power_state(struct pci_dev *dev, pci_power_t state);
+int pci_set_power_state_locked(struct pci_dev *dev, pci_power_t state);
pci_power_t pci_choose_state(struct pci_dev *dev, pm_message_t state);
bool pci_pme_capable(struct pci_dev *dev, pci_power_t state);
void pci_pme_active(struct pci_dev *dev, bool enable);
@@ -1594,6 +1595,8 @@ int pci_scan_bridge(struct pci_bus *bus,

void pci_walk_bus(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
void *userdata);
+void pci_walk_bus_locked(struct pci_bus *top, int (*cb)(struct pci_dev *, void *),
+ void *userdata);
int pci_cfg_space_size(struct pci_dev *dev);
unsigned char pci_bus_max_busnr(struct pci_bus *bus);
void pci_setup_bridge(struct pci_bus *bus);
@@ -1990,6 +1993,8 @@ static inline int pci_save_state(struct
static inline void pci_restore_state(struct pci_dev *dev) { }
static inline int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
{ return 0; }
+static inline int pci_set_power_state_locked(struct pci_dev *dev, pci_power_t state)
+{ return 0; }
static inline int pci_wake_from_d3(struct pci_dev *dev, bool enable)
{ return 0; }
static inline pci_power_t pci_choose_state(struct pci_dev *dev,