Re: Alan Cox quote? (was: Re: accounting for threads)

[Richard Gooch]

Alexander Viro writes:
> BTW, proc_net_create() is also not a good idea if you block the
> interrupts.  Ditto for netlink_kernel_create(), AFAICS (due to
> netlink_kernel_creat() -> sock_alloc() -> get_empty_inode() ->
> kmem_cache_alloc() with SLAB_KERNEL).
> 
> That, BTW, is a nice illustration - it's easy to get a preemption
> point without noticing, so holding spinlocks, let alone disabling
> interrupts over the large area is going to hurt like hell.

Here's an idea: add a CONFIGable debug mode for spinlock/cli
interaction with GFP_KERNEL and other (known) blocking operations.
Keep a per-CPU flag or bitmask that's manipulated by lock/cli
operations and checked by memory allocators and other key blocking
operations. Generate an Oops upon violation.

Make the CONFIG option initially set to 'y' for a patch level or two.

				Regards,

					Richard....
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