| Message ID | 20170118234612.26157.95913.stgit@bhelgaas-glaptop.roam.corp.google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On Wed, Jan 18, 2017 at 05:46:12PM -0600, Bjorn Helgaas wrote: > 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> Applied to pci/enumeration for v4.11. > --- > 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 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); > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pci" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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);
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> --- drivers/pci/access.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html