From: Bjorn Helgaas Date: Sat, 7 Oct 2017 22:37:34 +0000 (+0000) Subject: PCI: Avoid possible deadlock on pci_lock and p->pi_lock X-Git-Tag: C0P2-H0.0--20200415~6897 X-Git-Url: https://git.somdevices.com/?a=commitdiff_plain;h=df0c2d409e9d3159724b206da7e7e697fb5874eb;p=linux.git PCI: Avoid possible deadlock on pci_lock and p->pi_lock [ 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 Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- 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);