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| author | Lukas Wunner <lukas@wunner.de> | 2016-10-28 10:52:06 +0200 |
|---|---|---|
| committer | Bjorn Helgaas <bhelgaas@google.com> | 2016-11-17 18:43:49 -0600 |
| commit | 738a7edbfc7b623e276686dead046c9f3aae6b2e (patch) | |
| tree | e3abc850064b58a1c32682189ec34be25b8deefc /drivers/pci/pci.c | |
| parent | ccdb6be9ec6580ef69f68949ebe26e0fb58a6fb0 (diff) | |
| download | linux-738a7edbfc7b623e276686dead046c9f3aae6b2e.tar.bz2 | |
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.c')
| -rw-r--r-- | drivers/pci/pci.c | 3 |
1 files changed, 0 insertions, 3 deletions
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index eda6a7cf0e54..5d6f2970fd6f 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -2296,7 +2296,6 @@ static void pci_bridge_d3_update(struct pci_dev *dev, bool remove) if (!bridge || !pci_bridge_d3_possible(bridge)) return; - pci_dev_get(bridge); /* * If the device is removed we do not care about its D3cold * capabilities. @@ -2318,8 +2317,6 @@ static void pci_bridge_d3_update(struct pci_dev *dev, bool remove) /* Propagate change to upstream bridges */ pci_bridge_d3_update(bridge, false); } - - pci_dev_put(bridge); } /** |