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    SubjectRe: spinlock assertion macros
    On Thu, Jul 11, 2002 at 12:24:06AM +0200, Daniel Phillips wrote:
    > Acme, which is to replace all those above-the-function lock coverage
    > comments with assert-like thingies:
    > spin_assert(&pagemap_lru_lock);
    > And everbody knows what that does: when compiled with no spinlock
    > debugging it does nothing, but with spinlock debugging enabled, it oopses
    > unless pagemap_lru_lock is held at that point in the code. The practical
    > effect of this is that lots of 3 line comments get replaced with a
    > one line assert that actually does something useful. That is, besides
    > documenting the lock coverage, this thing will actually check to see if
    > you're telling the truth, if you ask it to.
    > Oh, and they will stay up to date much better than the comments do,
    > because nobody needs to to be an ueber-hacker to turn on the option and
    > post any resulting oopses to lkml.

    Sounds like a great idea to me. Were you thinking of something along
    the lines of what I have below or perhaps something more
    sophisticated? I suppose it would be helpful to have the name of the
    lock in addition to the file and line number...


    diff -Naur -X /home/jbarnes/dontdiff linux-2.5.25/fs/inode.c linux-2.5.25-spinassert/fs/inode.c
    --- linux-2.5.25/fs/inode.c Fri Jul 5 16:42:38 2002
    +++ linux-2.5.25-spinassert/fs/inode.c Wed Jul 10 16:30:18 2002
    @@ -183,6 +183,8 @@
    void __iget(struct inode * inode)
    + spin_assert_locked(&inode_lock);
    if (atomic_read(&inode->i_count)) {
    diff -Naur -X /home/jbarnes/dontdiff linux-2.5.25/include/linux/spinlock.h linux-2.5.25-spinassert/include/linux/spinlock.h
    --- linux-2.5.25/include/linux/spinlock.h Fri Jul 5 16:42:24 2002
    +++ linux-2.5.25-spinassert/include/linux/spinlock.h Wed Jul 10 16:20:06 2002
    @@ -118,6 +118,18 @@

    #endif /* !SMP */

    + * Simple lock assertions for debugging and documenting where locks need
    + * to be locked/unlocked.
    + */
    +#define spin_assert_locked(lock) if (!spin_is_locked(lock)) { printk("lock assertion failure: lock at %s:%d should be locked!\n", __FILE__, __LINE__); }
    +#define spin_assert_unlocked(lock) if (spin_is_locked(lock)) { printk("lock assertion failure: lock at %s:%d should be unlocked!\n", __FILE__, __LINE__); }
    +#define spin_assert_locked(lock) do { } while(0)
    +#define spin_assert_unlocked(lock) do { } while(0)
    +#endif /* CONFIG_DEBUG_SPINLOCK */

    asmlinkage void preempt_schedule(void);
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