Re: I request inclusion of reiser4 in the mainline kernel

From: Nikita Danilov (nikita_at_clusterfs.com)
Date: 09/30/05

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    Date:	Fri, 30 Sep 2005 21:27:20 +0400
To: "Vladimir V. Saveliev" <vs@namesys.com>

    Vladimir V. Saveliev writes:
    > Hello
    >
    > Christoph Hellwig wrote:
    > > ...
    > > Looking at the actual code all these point to the spin lock obsufcation
    > > SPIN_LOCK_FUNCTIONS/RW_LOCK_FUNCTIONS from spin_macros.h which I told
    > > to get rid of in the first round of reviews.
    > > ...
    >
    > reiser4 spinlock macros provide following functionality:
    >
    > (1) encapsulation of locks: instead of writing spin_lock(&obj->lock),
    > where obj is object of type foo, one writes spin_lock_foo(obj).
    >
    > (2) keeping information about number of locks of particular type currently
    > held by thread
    >
    > (3) checking that locks are acquired in the proper order.
    >
    > (4) collection of spin lock contention statistics
    >
    >
    > I agree that (1) is not very necessary. (2) and (4) helped a lot in early
    > debugging. Now we are about to remove it.

    This was already discussed during earlier attempts to merge reiser4. The
    proper solution purportedly is to make useful features of reiser4
    spin-lock code generic and merge them so that the rest of kernel can
    enjoy their superiority.

    >
    > However, we would prefer to keep (3). It makes catching spinlock deadlocks very
    > easy. Don't you think that makes sence?

    Lock-ordering monitoring was _immensely_ useful. For one thing it forces
    one to have complete and up to date description of lock ordering.

    >
    > Thanks

    Nikita.
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