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40f11adc7c
When we enable a device, we first enable any upstream bridges. If a bridge has multiple downstream devices and we enable them simultaneously, the race to enable the upstream bridge may cause problems. Consider this hierarchy: bridge A --+-- device B +-- device C If drivers for B and C call pci_enable_device() simultaneously, both will attempt to enable A, which involves setting PCI_COMMAND_MASTER via pci_set_master() and PCI_COMMAND_MEMORY via pci_enable_resources(). In the following sequence, B's update to set A's PCI_COMMAND_MEMORY is lost, and neither B nor C will work correctly: B C pci_set_master(A) cmd = read(A, PCI_COMMAND) cmd |= PCI_COMMAND_MASTER pci_set_master(A) cmd = read(A, PCI_COMMAND) cmd |= PCI_COMMAND_MASTER write(A, PCI_COMMAND, cmd) pci_enable_device(A) pci_enable_resources(A) cmd = read(A, PCI_COMMAND) cmd |= PCI_COMMAND_MEMORY write(A, PCI_COMMAND, cmd) write(A, PCI_COMMAND, cmd) Avoid this race by holding a new pci_bridge_mutex while enabling a bridge. This ensures that both PCI_COMMAND_MASTER and PCI_COMMAND_MEMORY will be updated before another thread can start enabling the bridge. Note that although pci_enable_bridge() is recursive, it enables any upstream bridges *before* acquiring the mutex. When it acquires the mutex and calls pci_set_master() and pci_enable_device(), any upstream bridges have already been enabled so pci_enable_device() will not deadlock by calling pci_enable_bridge() again. Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com> [bhelgaas: changelog, comment] Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> |
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.. | ||
dwc | ||
endpoint | ||
host | ||
hotplug | ||
pcie | ||
switch | ||
access.c | ||
ats.c | ||
bus.c | ||
ecam.c | ||
host-bridge.c | ||
hotplug-pci.c | ||
htirq.c | ||
iov.c | ||
irq.c | ||
Kconfig | ||
Makefile | ||
mmap.c | ||
msi.c | ||
of.c | ||
pci-acpi.c | ||
pci-driver.c | ||
pci-label.c | ||
pci-mid.c | ||
pci-stub.c | ||
pci-sysfs.c | ||
pci.c | ||
pci.h | ||
probe.c | ||
proc.c | ||
quirks.c | ||
remove.c | ||
rom.c | ||
search.c | ||
setup-bus.c | ||
setup-irq.c | ||
setup-res.c | ||
slot.c | ||
syscall.c | ||
vc.c | ||
vpd.c | ||
xen-pcifront.c |