> -----Original Message----- > From: Alan Stern [mailto:stern@xxxxxxxxxxxxxxxxxxx] > Sent: Wednesday, April 06, 2011 11:16 PM > To: Roedel, Joerg > Cc: Greg Kroah-Hartman; Sarah Sharp; Xu, Andiry; linux-usb@xxxxxxxxxxxxxxx; > linux-kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxx > Subject: Re: [PATCH] USB host: Fix lockdep warning in AMD PLL quirk > > On Wed, 6 Apr 2011, Joerg Roedel wrote: > > > Booting 2.6.38 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 > > 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 for me. > > > > Cc: stable@xxxxxxxxxx > > Signed-off-by: Joerg Roedel <joerg.roedel@xxxxxxx> > > --- > > drivers/usb/host/pci-quirks.c | 67 +++++++++++++++++++++++----------- > ------ > > 1 files changed, 38 insertions(+), 29 deletions(-) > > > > diff --git a/drivers/usb/host/pci-quirks.c b/drivers/usb/host/pci- > quirks.c > > index 1d586d4..d3e5cf3 100644 > > --- a/drivers/usb/host/pci-quirks.c > > +++ b/drivers/usb/host/pci-quirks.c > > @@ -84,64 +84,73 @@ int usb_amd_find_chipset_info(void) > > { > > u8 rev = 0; > > unsigned long flags; > > + struct pci_dev *nb_dev, *smbus_dev; > > + int nb_type, sb_type; > > > > spin_lock_irqsave(&amd_lock, flags); > > - > > amd_chipset.probe_count++; > > /* probe only once */ > > if (amd_chipset.probe_count > 1) { > > spin_unlock_irqrestore(&amd_lock, flags); > > return amd_chipset.probe_result; > > } > > The counter really should be a bool: Has the chipset already been > probed or not? After all, nobody cares how many times this routine was > called. > The probe routine increases probe_count counter to remember how many hosts calls it. Every host that calls probe routine in initialization will call usb_amd_dev_put() in *hci_stop() and decrease probe_count, so the last caller can safely free the resources. Thanks, Andiry -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
