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author | Lukas Wunner <lukas@wunner.de> | 2016-10-28 11:52:06 +0300 |
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committer | Bjorn Helgaas <bhelgaas@google.com> | 2016-11-18 03:43:49 +0300 |
commit | 738a7edbfc7b623e276686dead046c9f3aae6b2e (patch) | |
tree | e3abc850064b58a1c32682189ec34be25b8deefc /drivers/pci/pci.h | |
parent | ccdb6be9ec6580ef69f68949ebe26e0fb58a6fb0 (diff) | |
download | linux-738a7edbfc7b623e276686dead046c9f3aae6b2e.tar.xz |
PCI: Don't acquire ref on parent in pci_bridge_d3_update()
This function is always called with an existing pci_dev struct, which
holds a reference on the pci_bus struct it resides on, which in turn
holds a reference on pci_bus->bridge, which is the pci_dev's parent.
Hence there's no need to acquire an additional ref on the parent.
More specifically, the pci_dev exists until pci_destroy_dev() drops the
final reference on it, so all calls to pci_bridge_d3_update() must be
finished before that. It is arguably the caller's responsibility to ensure
that it doesn't call pci_bridge_d3_update() with a pci_dev that might
suddenly disappear, but in any case the existing callers are all safe:
- The call in pci_destroy_dev() happens before the call to put_device().
- The call in pci_bus_add_device() is synchronized with pci_destroy_dev()
using pci_lock_rescan_remove().
- The calls to pci_d3cold_disable() from the xhci and nouveau drivers
are safe because a ref on the pci_dev is held as long as it's bound to
a driver.
- The calls to pci_d3cold_enable() / pci_d3cold_disable() when modifying
the sysfs "d3cold_allowed" entry are also safe because kernfs_drain()
waits for existing sysfs users to finish before removing the entry,
and pci_destroy_dev() is called way after that.
No functional change intended.
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/pci/pci.h')
0 files changed, 0 insertions, 0 deletions