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Date: Mon, 11 Apr 2011 08:26:00 +0200
From: Borislav Petkov <bp@...en8.de>
To: Joerg Roedel <joerg.roedel@....com>
Cc: Greg Kroah-Hartman <gregkh@...e.de>,
Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
Andiry Xu <andiry.xu@....com>,
Alan Stern <stern@...land.harvard.edu>,
linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
stable@...nel.org
Subject: Re: [PATCH] USB host: Fix lockdep warning in AMD PLL quirk
On Thu, Apr 07, 2011 at 03:14:04PM +0200, Joerg Roedel wrote:
> Booting 2.6.38 on my test machine produces a lockdep warning
You mean 2.6.39-rc2 right? I'm asking because I hit the same warning
with 39-rc2 now too but it didn't appear with .38 - so it has to have
snuck in after the merge window. If so, you don't need the stable tag.
Also, is this the final version wrt code design so that I can test too?
Thanks.
> 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
> sr0: scsi3-mmc drive: 48x/48x writer dvd-ram cd/rw xa/form2 cdda tray
> [<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 this by using temporary variables in the quirk
> algorithm and commiting them later to the struct under the lock. This
> moves all pci_get_device() invocations out of the spin_lock and fixes
> the lockdep warning.
>
> Cc: stable@...nel.org
> Signed-off-by: Joerg Roedel <joerg.roedel@....com>
> ---
> drivers/usb/host/pci-quirks.c | 90 +++++++++++++++++++++++++---------------
> 1 files changed, 56 insertions(+), 34 deletions(-)
>
> diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci-quirks.c
> index 1d586d4..c21b073 100644
> --- a/drivers/usb/host/pci-quirks.c
> +++ b/drivers/usb/host/pci-quirks.c
> @@ -84,65 +84,87 @@ 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) {
> spin_unlock_irqrestore(&amd_lock, flags);
> return amd_chipset.probe_result;
> }
> + info = amd_chipset;
> + 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");
>
> +commit:
> +
> + spin_lock_irqsave(&amd_lock, flags);
> + if (amd_chipset.probe_count > 0) {
> + /* race - someone else was faster - drop devices */
> + if (info.nb_dev)
> + pci_dev_put(info.nb_dev);
> + if (info.smbus_dev)
> + pci_dev_put(info.smbus_dev);
> +
> + /* Mark that we where here */
> + amd_chipset.probe_count++;
> + ret = amd_chipset.probe_result;
> + } else {
> + /* no race - commit the result */
> + info.probe_count++;
> + amd_chipset = info;
> + }
> spin_unlock_irqrestore(&amd_lock, flags);
> - return amd_chipset.probe_result;
> +
> + return ret;
> }
> EXPORT_SYMBOL_GPL(usb_amd_find_chipset_info);
>
> --
> 1.7.1
>
>
> --
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--
Regards/Gruss,
Boris.
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