Messages in this thread Patch in this message | | | From | "Levin, Alexander (Sasha Levin)" <> | Subject | [PATCH review for 4.9 50/50] PCI: Avoid possible deadlock on pci_lock and p->pi_lock | Date | Sat, 7 Oct 2017 22:37:34 +0000 |
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From: Bjorn Helgaas <bhelgaas@google.com>
[ Upstream commit cdcb33f9824429a926b971bf041a6cec238f91ff ]
pci_lock is an IRQ-safe spinlock that protects all accesses to PCI configuration space (see PCI_OP_READ() and PCI_OP_WRITE() in pci/access.c).
The pci_cfg_access_unlock() path acquires pci_lock, then p->pi_lock (inside wake_up_all()). According to lockdep, there is a possible path involving snbep_uncore_pci_read_counter() that could acquire them in the reverse order: acquiring p->pi_lock, then pci_lock, which could result in a deadlock. Lockdep details are in the bugzilla below.
Avoid the possible deadlock by dropping pci_lock before waking up any config access waiters.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=192901 Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Signed-off-by: Sasha Levin <alexander.levin@verizon.com> --- drivers/pci/access.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/pci/access.c b/drivers/pci/access.c index d11cdbb8fba3..7b5cf6d1181a 100644 --- a/drivers/pci/access.c +++ b/drivers/pci/access.c @@ -672,8 +672,9 @@ void pci_cfg_access_unlock(struct pci_dev *dev) WARN_ON(!dev->block_cfg_access); dev->block_cfg_access = 0; - wake_up_all(&pci_cfg_wait); raw_spin_unlock_irqrestore(&pci_lock, flags); + + wake_up_all(&pci_cfg_wait); } EXPORT_SYMBOL_GPL(pci_cfg_access_unlock); -- 2.11.0
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