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| author | Bjorn Helgaas <bhelgaas@google.com> | 2017-01-13 18:05:12 -0600 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2017-01-30 16:55:33 -0600 |
| commit | cdcb33f9824429a926b971bf041a6cec238f91ff (patch) | |
| tree | 05668a16f75570f3a408b762ea2462180cb26a30 /drivers/pci/access.c | |
| parent | 53762ba810398c11efaf65f9a45d992125e86dcf (diff) | |
| download | lwn-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.c | 3 |
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); |