On Mon, Apr 11, 2011 at 01:05:41PM -0400, Alan Stern wrote:
> On Mon, 11 Apr 2011, Roedel, Joerg wrote:
> > Hmm, I see how it can be done differently, but no real bug.
>
> Never mind, you're right. In the no-race case, the initial count is
> always going to be 0, and so incrementing info.probe_count is the right
> thing to do.
Okay, cool. So now that we have settled on this I removed the last
occurence of '2.6.38' from the changelog and here is the result. No
code changes since v5.
>From a6e00d237f20e940afdbcaafb27117fe8730466f Mon Sep 17 00:00:00 2001
From: Joerg Roedel <joerg.roedel@xxxxxxx>
Date: Wed, 6 Apr 2011 13:07:53 +0200
Subject: [PATCH] USB host: Fix lockdep warning in AMD PLL quirk
Booting latest kernel on my test machine produces a lockdep
warning from the usb_amd_find_chipset_info() function:
WARNING: at /data/lemmy/linux.trees.git/kernel/lockdep.c:2465 lockdep_trace_alloc+0x95/0xc2()
Hardware name: Snook
Modules linked in:
Pid: 959, comm: work_for_cpu Not tainted 2.6.39-rc2+ #22
Call Trace:
[<ffffffff8103c0d4>] warn_slowpath_common+0x80/0x98
[<ffffffff812387e6>] ? T.492+0x24/0x26
[<ffffffff8103c101>] warn_slowpath_null+0x15/0x17
[<ffffffff81068667>] lockdep_trace_alloc+0x95/0xc2
[<ffffffff810ed9ac>] slab_pre_alloc_hook+0x18/0x3b
[<ffffffff810ef227>] kmem_cache_alloc_trace+0x25/0xba
[<ffffffff812387e6>] T.492+0x24/0x26
[<ffffffff81238816>] pci_get_subsys+0x2e/0x73
[<ffffffff8123886c>] pci_get_device+0x11/0x13
[<ffffffff814082a9>] usb_amd_find_chipset_info+0x3f/0x18a
...
It turns out that this function calls pci_get_device under a spin_lock
with irqs disabled, but the pci_get_device function is only allowed in
preemptible context.
This patch fixes the warning by making all data-structure
modifications on temporal storage and commiting this back
into the visible structure at the end. While at it, this
patch also moves the pci_dev_put calls out of the spinlocks
because this function might sleep too.
Signed-off-by: Joerg Roedel <joerg.roedel@xxxxxxx>
---
drivers/usb/host/pci-quirks.c | 117 ++++++++++++++++++++++++++---------------
1 files changed, 74 insertions(+), 43 deletions(-)
diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
index 1d586d4..c6eb69c 100644
--- a/drivers/usb/host/pci-quirks.c
+++ b/drivers/usb/host/pci-quirks.c
@@ -84,65 +84,92 @@ int usb_amd_find_chipset_info(void)
{
u8 rev = 0;
unsigned long flags;
+ struct amd_chipset_info info;
+ int ret;
spin_lock_irqsave(&amd_lock, flags);
- amd_chipset.probe_count++;
/* probe only once */
- if (amd_chipset.probe_count > 1) {
+ if (amd_chipset.probe_count > 0) {
+ amd_chipset.probe_count++;
spin_unlock_irqrestore(&amd_lock, flags);
return amd_chipset.probe_result;
}
+ memset(&info, 0, sizeof(info));
+ spin_unlock_irqrestore(&amd_lock, flags);
- amd_chipset.smbus_dev = pci_get_device(PCI_VENDOR_ID_ATI, 0x4385, NULL);
- if (amd_chipset.smbus_dev) {
- rev = amd_chipset.smbus_dev->revision;
+ info.smbus_dev = pci_get_device(PCI_VENDOR_ID_ATI, 0x4385, NULL);
+ if (info.smbus_dev) {
+ rev = info.smbus_dev->revision;
if (rev >= 0x40)
- amd_chipset.sb_type = 1;
+ info.sb_type = 1;
else if (rev >= 0x30 && rev <= 0x3b)
- amd_chipset.sb_type = 3;
+ info.sb_type = 3;
} else {
- amd_chipset.smbus_dev = pci_get_device(PCI_VENDOR_ID_AMD,
- 0x780b, NULL);
- if (!amd_chipset.smbus_dev) {
- spin_unlock_irqrestore(&amd_lock, flags);
- return 0;
+ info.smbus_dev = pci_get_device(PCI_VENDOR_ID_AMD,
+ 0x780b, NULL);
+ if (!info.smbus_dev) {
+ ret = 0;
+ goto commit;
}
- rev = amd_chipset.smbus_dev->revision;
+
+ rev = info.smbus_dev->revision;
if (rev >= 0x11 && rev <= 0x18)
- amd_chipset.sb_type = 2;
+ info.sb_type = 2;
}
- if (amd_chipset.sb_type == 0) {
- if (amd_chipset.smbus_dev) {
- pci_dev_put(amd_chipset.smbus_dev);
- amd_chipset.smbus_dev = NULL;
+ if (info.sb_type == 0) {
+ if (info.smbus_dev) {
+ pci_dev_put(info.smbus_dev);
+ info.smbus_dev = NULL;
}
- spin_unlock_irqrestore(&amd_lock, flags);
- return 0;
+ ret = 0;
+ goto commit;
}
- amd_chipset.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD, 0x9601, NULL);
- if (amd_chipset.nb_dev) {
- amd_chipset.nb_type = 1;
+ info.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD, 0x9601, NULL);
+ if (info.nb_dev) {
+ info.nb_type = 1;
} else {
- amd_chipset.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD,
- 0x1510, NULL);
- if (amd_chipset.nb_dev) {
- amd_chipset.nb_type = 2;
- } else {
- amd_chipset.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD,
- 0x9600, NULL);
- if (amd_chipset.nb_dev)
- amd_chipset.nb_type = 3;
+ info.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD, 0x1510, NULL);
+ if (info.nb_dev) {
+ info.nb_type = 2;
+ } else {
+ info.nb_dev = pci_get_device(PCI_VENDOR_ID_AMD,
+ 0x9600, NULL);
+ if (info.nb_dev)
+ info.nb_type = 3;
}
}
- amd_chipset.probe_result = 1;
+ ret = info.probe_result = 1;
printk(KERN_DEBUG "QUIRK: Enable AMD PLL fix\n");
- spin_unlock_irqrestore(&amd_lock, flags);
- return amd_chipset.probe_result;
+commit:
+
+ spin_lock_irqsave(&amd_lock, flags);
+ if (amd_chipset.probe_count > 0) {
+ /* race - someone else was faster - drop devices */
+
+ /* Mark that we where here */
+ amd_chipset.probe_count++;
+ ret = amd_chipset.probe_result;
+
+ spin_unlock_irqrestore(&amd_lock, flags);
+
+ if (info.nb_dev)
+ pci_dev_put(info.nb_dev);
+ if (info.smbus_dev)
+ pci_dev_put(info.smbus_dev);
+
+ } else {
+ /* no race - commit the result */
+ info.probe_count++;
+ amd_chipset = info;
+ spin_unlock_irqrestore(&amd_lock, flags);
+ }
+
+ return ret;
}
EXPORT_SYMBOL_GPL(usb_amd_find_chipset_info);
@@ -284,6 +311,7 @@ EXPORT_SYMBOL_GPL(usb_amd_quirk_pll_enable);
void usb_amd_dev_put(void)
{
+ struct pci_dev *nb, *smbus;
unsigned long flags;
spin_lock_irqsave(&amd_lock, flags);
@@ -294,20 +322,23 @@ void usb_amd_dev_put(void)
return;
}
- if (amd_chipset.nb_dev) {
- pci_dev_put(amd_chipset.nb_dev);
- amd_chipset.nb_dev = NULL;
- }
- if (amd_chipset.smbus_dev) {
- pci_dev_put(amd_chipset.smbus_dev);
- amd_chipset.smbus_dev = NULL;
- }
+ /* save them to pci_dev_put outside of spinlock */
+ nb = amd_chipset.nb_dev;
+ smbus = amd_chipset.smbus_dev;
+
+ amd_chipset.nb_dev = NULL;
+ amd_chipset.smbus_dev = NULL;
amd_chipset.nb_type = 0;
amd_chipset.sb_type = 0;
amd_chipset.isoc_reqs = 0;
amd_chipset.probe_result = 0;
spin_unlock_irqrestore(&amd_lock, flags);
+
+ if (nb)
+ pci_dev_put(nb);
+ if (smbus)
+ pci_dev_put(amd_chipset.smbus_dev);
}
EXPORT_SYMBOL_GPL(usb_amd_dev_put);
--
1.7.1
--
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Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632
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