Re: [CHECKER] potential deadlocks

Andrew Morton (
Sun, 2 Mar 2003 21:25:00 -0800

Dawson Engler <> wrote:
> Any feedback on the results would be great. My understanding of linux's
> sprawling locking rules is less than impressive.

We would be impressed if it wasn't :)

> Also, if there are
> known deadlocks, let me know and I can make sure we're finding them.

There are some real ones there. The ones surrounding lock_kernel() and
semaphores are false positives.

lock_kernel() is special, in that the lock is dropped when the caller
performs a voluntary context switch. So there are no ordering requirements
between lock_kernel and the sleeping locks down(), down_read(), down_write().

lock_kernel() inside a spinlock is not necessarily a bug, but almost always
is. It should be warned about.

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