Re: [PATCH 1/1] tpm: fix cause of SMP stack traces

Kylene Hall
2005-01-18T22:44:55Z

On Tue, 2005-01-18 at 16:37, Chris Wright wrote:
> * Kylene Hall (kjhall@us.ibm.com) wrote:
> > There were misplaced spinlock acquires and releases in the probe, open,
> > close and release paths which were causing might_sleep and schedule while
> > atomic error messages accompanied by stack traces when the kernel was
> > compiled with SMP support. Bug reported by Reben Jenster
> > <ruben@hotheads.de>
> >
> > Signed-off-by: Kylene Hall <kjhall@us.ibm.com>
> > ---
> > diff -uprN linux-2.6.10/drivers/char/tpm/tpm.c linux-2.6.10-tpm/drivers/char/tpm/tpm.c
> > --- linux-2.6.10/drivers/char/tpm/tpm.c 2005-01-18 16:42:17.000000000 -0600
> > +++ linux-2.6.10-tpm/drivers/char/tpm/tpm.c 2005-01-18 12:52:53.000000000 -0600
> > @@ -373,8 +372,9 @@ int tpm_open(struct inode *inode, struct
> > {
> > int rc = 0, minor = iminor(inode);
> > struct tpm_chip *chip = NULL, *pos;
> > + unsigned long flags;
> >
> > - spin_lock(&driver_lock);
> > + spin_lock_irqsave(&driver_lock, flags);
>
> Hmm, unless I'm missing something, this is only worse (for might sleep
> warnings). Now you've disabled irq's too.

I actually had to move the location of some of the locks to remove the
might sleep warnings. Since I didn't know much about the might sleep
warnings before, my first course of action was to try using the disable
irq mechanism and I went ahead and just left them in once it was working
with the new lock placements. I assume you believe they shouldn't be
necessary at all?

Thanks,
Kylie

>
> thanks,
> -chris