On 2015/3/12 10:55, Bjorn Helgaas wrote: > On Mon, Mar 09, 2015 at 10:34:07AM +0800, Yijing Wang wrote: >> Introduce pci_host_bridge_list to manage pci host >> bridges in system, so we could detect whether >> the host in domain:bus is alreay registered. >> Then we could remove bus alreay exist test in >> __pci_create_root_bus(). > > It's a nice idea to move this test into the core. While you're at it, why > don't you check for any overlap with the bus ranges of existing host > bridges? For example, if we're trying to create a new host bridge to > [bus 40-7f], it should conflict with existing bridges to [bus 00-7f] > as well as to [bus 40-ff]. I think your current patch will detect the > latter conflict but not the former.
Now pci host bridge may only know its start bus number, like acpi _BBN provided, but does not limit the end bus number, Eg. two pci roots report _BBN 0x0 and 0x80, so we have two bus number resource (0, 0xff) and (0x80, 0xff), if we check it strictly, some pci scan would fail which currently scan success. > >> Signed-off-by: Yijing Wang <[email protected]> >> Signed-off-by: Bjorn Helgaas <[email protected]> >> --- >> drivers/pci/host-bridge.c | 24 +++++++++++++++++++++++- >> drivers/pci/probe.c | 8 +------- >> include/linux/pci.h | 1 + >> 3 files changed, 25 insertions(+), 8 deletions(-) >> >> diff --git a/drivers/pci/host-bridge.c b/drivers/pci/host-bridge.c >> index 3bd45e7..0bb08ef 100644 >> --- a/drivers/pci/host-bridge.c >> +++ b/drivers/pci/host-bridge.c >> @@ -8,6 +8,9 @@ >> >> #include "pci.h" >> >> +static LIST_HEAD(pci_host_bridge_list); >> +static DEFINE_MUTEX(phb_mutex); > > We don't use the "phb" abbreviation in the PCI core. OK > >> + >> static void pci_release_host_bridge_dev(struct device *dev) >> { >> struct pci_host_bridge *bridge = to_pci_host_bridge(dev); >> @@ -25,7 +28,7 @@ struct pci_host_bridge *pci_create_host_bridge( >> int error; >> int bus = PCI_BUSNUM(db); >> int domain = PCI_DOMAIN(db); >> - struct pci_host_bridge *host; >> + struct pci_host_bridge *host, *temp; >> struct resource_entry *window, *n; >> >> host = kzalloc(sizeof(*host), GFP_KERNEL); >> @@ -40,6 +43,18 @@ struct pci_host_bridge *pci_create_host_bridge( >> */ >> pci_host_assign_domain_nr(host); >> >> + mutex_lock(&phb_mutex); >> + list_for_each_entry(temp, &pci_host_bridge_list, list) >> + if (temp->domain == host->domain >> + && temp->busnum == host->busnum) { >> + dev_dbg(&host->dev, "pci host bridge pci%04x:%02x >> exist\n", >> + host->domain, host->busnum); > > &host->dev hasn't been initialized yet! And the text of the original > message was better. Oh, my mistake, good catch. > >> + mutex_unlock(&phb_mutex); >> + kfree(host); >> + return NULL; >> + } >> + mutex_unlock(&phb_mutex); > > This is racy. Two CPUs adding a bridge to [bus 00-7f] at about the same > time can both succeed. > Hmm, I need to unlock after I add the new host bridge to the gloal host bridge list, thanks. > And it needs curly braces around the list_for_each_entry() body. OK > >> + >> host->dev.parent = parent; >> INIT_LIST_HEAD(&host->windows); >> host->dev.release = pci_release_host_bridge_dev; >> @@ -55,11 +70,18 @@ struct pci_host_bridge *pci_create_host_bridge( >> resource_list_for_each_entry_safe(window, n, resources) >> list_move_tail(&window->node, &host->windows); >> >> + mutex_lock(&phb_mutex); >> + list_add_tail(&host->list, &pci_host_bridge_list); >> + mutex_unlock(&phb_mutex); >> return host; >> } >> >> void pci_free_host_bridge(struct pci_host_bridge *host) >> { >> + mutex_lock(&phb_mutex); >> + list_del(&host->list); >> + mutex_unlock(&phb_mutex); >> + >> device_unregister(&host->dev); >> } >> >> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c >> index 27ec612..7238fa3 100644 >> --- a/drivers/pci/probe.c >> +++ b/drivers/pci/probe.c >> @@ -1870,7 +1870,7 @@ static struct pci_bus *__pci_create_root_bus( >> void *sysdata) >> { >> int error; >> - struct pci_bus *b, *b2; >> + struct pci_bus *b; >> struct resource_entry *window; >> struct device *parent; >> struct resource *res; >> @@ -1887,12 +1887,6 @@ static struct pci_bus *__pci_create_root_bus( >> b->ops = ops; >> b->number = b->busn_res.start = bridge->busnum; >> pci_bus_assign_domain_nr(b, parent); >> - b2 = pci_find_bus(pci_domain_nr(b), b->number); >> - if (b2) { >> - /* If we already got to this bus through a different bridge, >> ignore it */ >> - dev_dbg(&b2->dev, "bus already known\n"); >> - goto err_out; >> - } >> >> bridge->bus = b; >> b->bridge = get_device(&bridge->dev); >> diff --git a/include/linux/pci.h b/include/linux/pci.h >> index 463eaa3..b621f5b 100644 >> --- a/include/linux/pci.h >> +++ b/include/linux/pci.h >> @@ -406,6 +406,7 @@ struct pci_host_bridge { >> struct device dev; >> struct pci_bus *bus; /* root bus */ >> struct list_head windows; /* resource_entry */ >> + struct list_head list; >> void (*release_fn)(struct pci_host_bridge *); >> void *release_data; >> }; >> -- >> 1.7.1 >> > > . > -- Thanks! Yijing -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
