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authorBjorn Helgaas <bhelgaas@google.com>2017-01-13 18:05:12 -0600
committerBjorn Helgaas <bhelgaas@google.com>2017-01-30 16:55:33 -0600
commitcdcb33f9824429a926b971bf041a6cec238f91ff (patch)
tree05668a16f75570f3a408b762ea2462180cb26a30 /drivers/pci/access.c
parent53762ba810398c11efaf65f9a45d992125e86dcf (diff)
downloadlwn-cdcb33f9824429a926b971bf041a6cec238f91ff.tar.gz
lwn-cdcb33f9824429a926b971bf041a6cec238f91ff.zip
PCI: Avoid possible deadlock on pci_lock and p->pi_lock
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>
Diffstat (limited to 'drivers/pci/access.c')
-rw-r--r--drivers/pci/access.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/drivers/pci/access.c b/drivers/pci/access.c
index db239547fefd..68bd7201d8bc 100644
--- a/drivers/pci/access.c
+++ b/drivers/pci/access.c
@@ -684,8 +684,9 @@ 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);