Re: [CHECKER] a couple potential deadlocks in 2.4.5-ac8

Linus Torvalds
2001-06-10T06:19:40Z

On Sat, 9 Jun 2001, Dawson Engler wrote:
> >
> > Good point. Spinlocks (with the exception of read-read locks, of course)
> > and semaphores will deadlock on recursive use, while the BKL has this
> > "process usage counter" recursion protection.
>
> Actually, it did show up all over the place --- I'd just selected two
> candidates to examine out of hundreds. (Checking call chains is
> strenous, even when you know what you're looking for.)

Sure.

> > Dawson - the user-mode access part is probably _the_ most interesting from
> > a lock checking standpoint, could you check doing the page fault case?
>
> Sure, it's a pretty interaction. To be sure about the rule: any *_user
> call can be treated as an implicit invocation of do_page_fault?

As a first approximation, yes. The exception cases are certain callers
that use kernel addresses and set_fs(KERNEL_DS) in order to "fake"
arguments to system calls etc, but I doubt they should need any
special-casing.

Linus