On Thu, 4 Sep 2008 15:19:46 +0100 Ben Hutchings <bhutchings@xxxxxxxxxxxxxx> wrote: > Matthew Wilcox wrote: > > On Wed, Sep 03, 2008 at 03:57:13PM -0700, Stephen Hemminger wrote: > > > Accessing the VPD area can take a long time. There are comments in the > > > SysKonnect vendor driver that it can take up to 25ms. The existing vpd > > > access code fails consistently on my hardware. It's bad but not that bad more details are: MIN MAX ------------------------------------------------------------------- write 1.8 ms 3.6 ms internal write cyles 0.7 ms 7.0 ms ------------------------------------------------------------------- over all program time 2.5 ms 10.6 ms read 1.3 ms 2.6 ms ------------------------------------------------------------------- over all 3.8 ms 13.2 ms Usable VPD is limited to 2K so worst case read is 27 seconds. Note: there doesn't appear to be an standard for VPD size register in PCI spec, but there is a device specific register. > > Wow, that's slow. If you were to try to read all 32k, it'd take more > > than three minutes! (I presume it doesn't actually have as much as 32k). > > > > > Change the access routines to: > > > * use a mutex rather than spinning with IRQ's disabled and lock held > > > * have a longer timeout > > > * call schedule while spinning to provide some responsivness > > > > I agree with your approach, but have one minor comment: > > > > > - spin_lock_irq(&vpd->lock); > > > + mutex_lock(&vpd->lock); > > > > This should be: > > > > + if (mutex_lock_interruptible(&vpd->lock)) > > + return -EINTR; > [...] > > This is fine for the sysfs case, but not if this is called during device > probe - we don't want signals to modprobe to break device initialisation, > do we? Why not, it makes sense to allow killing a stuck modprobe. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
