Messages in this thread Patch in this message | ![/](/images/icornerl.gif) | | From | Johan Hovold <> | Subject | [PATCH 3/6] PCI: qcom: Fix deadlock when enabling ASPM | Date | Tue, 14 Nov 2023 14:55:50 +0100 |
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The qcom_pcie_enable_aspm() helper is called from pci_walk_bus() during host init to enable ASPM.
Since pci_walk_bus() already holds a pci_bus_sem read lock, use the new locked helper to enable link states in order to avoid a potential deadlock (e.g. in case someone takes a write lock before reacquiring the read lock).
This issue was reported by lockdep:
============================================ WARNING: possible recursive locking detected 6.7.0-rc1 #4 Not tainted -------------------------------------------- kworker/u16:6/147 is trying to acquire lock: ffffbf3ff9d2cfa0 (pci_bus_sem){++++}-{3:3}, at: pci_enable_link_state+0x74/0x1e8
but task is already holding lock: ffffbf3ff9d2cfa0 (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 ***
Fixes: 9f4f3dfad8cf ("PCI: qcom: Enable ASPM for platforms supporting 1.9.0 ops") Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> Signed-off-by: Johan Hovold <johan+linaro@kernel.org> --- drivers/pci/controller/dwc/pcie-qcom.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/pci/controller/dwc/pcie-qcom.c b/drivers/pci/controller/dwc/pcie-qcom.c index ce3ece28fed2..21523115f6a4 100644 --- a/drivers/pci/controller/dwc/pcie-qcom.c +++ b/drivers/pci/controller/dwc/pcie-qcom.c @@ -971,7 +971,7 @@ static int qcom_pcie_enable_aspm(struct pci_dev *pdev, void *userdata) { /* Downstream devices need to be in D0 state before enabling PCI PM substates */ pci_set_power_state(pdev, PCI_D0); - pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL); + pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL); return 0; } -- 2.41.0
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