On Fri, 12 Jul 2002, Daniel Phillips wrote:
> On Friday 12 July 2002 14:07, Dave Jones wrote:
> > On Thu, Jul 11, 2002 at 09:17:44PM +0200, Daniel Phillips wrote:
> > > On Thursday 11 July 2002 20:03, Jesse Barnes wrote:
> > > > How about this?
> > >
> > > It looks good, the obvious thing we don't get is what the actual lock
> > > count is, and actually, we don't care because we know what it is in
> > > this case.
> >
> > Something I've been meaning to hack up for a while is some spinlock
> > debugging code that adds a FUNCTION_SLEEPS() to (ta-da) functions that
> > may sleep.
>
> Yesss. May I suggest simply SLEEPS()? (Chances are, we know it's a
> function.)
>
> > This macro then checks whether we're currently holding any
> > locks, and if so printk's the names of locks held, and where they were taken.
>
> And then oopes?
>
> > When I came up with the idea[1] I envisioned some linked-lists frobbing,
> > but in more recent times, we can now check the preempt_count for a
> > quick-n-dirty implementation (without the additional info of which locks
> > we hold, lock-taker, etc).
>
> Spin_lock just has to store the address/location of the lock in a
> per-cpu vector, and the assert prints that out when it oopses. Such
> bugs won't live too long under those conditions.
Store it in the task struct, and store a pointer to the previous (outer
lock) in that lock, then you've got a linked list of locks per task - very
useful. You'll need a helper function - current() is hard to get at from
spinlock.h due to tangled dependencies. As I mentioned before, it can also
be very handy to stash the address of the code that took the lock in the
lock itself.
> Any idea how one might implement NEVER_SLEEPS()? Maybe as:
>
> NEVER_ [code goes here] _SLEEPS
>
> which inc/dec the preeempt count, triggering a BUG in schedule().
NEVER_SLEEPS will only trigger on the rare events that blow up anyway,
while the MAY_SLEEP version catches _potential_ problems even when the
fatal sleep doesn't happen.
-- "Love the dolphins," she advised him. "Write by W.A.S.T.E.."- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Mon Jul 15 2002 - 22:00:24 EST