lkml.org 
[lkml]   [2009]   [Apr]   [22]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] netfilter: use per-cpu recursive lock (v11)
    Linus Torvalds a écrit :
    >
    > On Wed, 22 Apr 2009, Eric Dumazet wrote:
    >> If this could be done without recursion, I am pretty sure netfilter
    >> and network guys would have done it. I found Linus reaction quite
    >> shocking IMHO, considering hard work done by all people on this.
    >
    > You don't _understand_ do you?
    >
    > There is a huge difference between recursive code, and a recursive lock.
    >
    > The netfilter code may need to occasionally re-enter itself. Nobody ever
    > contested _that_ part.
    >
    > What I have disagreed with the whole time is
    >
    > (a) doing local ad-hoc locking primitives without any comments
    > what-so-ever.
    >
    > (b) Doing them _wrong_ in many cases
    >
    > (c) Calling the _lock_ a "recursive" lock.
    >
    > The fact that a lock works with recursion doesn't make it "recursive".
    > That generally has a very special meaning for locking primitives, and
    > means something else.
    >
    > In contrast, a read-write lock actually has known properties, and we have
    > existing locking mechanisms for those. And we call them read-write locks
    > DESPITE THE FACT that the reading part can be done recursively.
    >
    > If you call a read-write lock a "recursive" lock, then you're a moron.
    > It simply is _not_ a recursive lock. And neither is the lock you actually
    > implemented, even though you (and Stephen) continually call it that.
    >
    > SO STOP CALLING IT A RECURSIVE LOCK. Look at your very own code: you can
    > actually only use that lock in a recursive context in a _very_ specific
    > place. Notice how it's only "recursive" when taken in the per-CPU context,
    > but _not_ recursive when the filter-updating code ("writer") takes it?
    >
    > Do you understand now? It really shouldn't be so hard for you.
    >
    > Naming is important. Locking is important. You did both things wrong. You
    > named your locks something incorrect and mis-leading that didn't actually
    > describe them, and you did your own private locking code without then
    > documenting what the rules for this special lock were.
    >
    > Maybe in your world that's ok. But no, in mine it's not. I've seen too
    > many damn _non-functioning_ locks to ever want to see stuff like that
    > again.
    >
    >

    Linus,

    I actually sent *one* buggy patch, and you already gave your feedback and NACK.

    Fine

    I even relayed this to Stephen suggesting him not calling this a recursive lock.
    (Note how I use 'suggesting' here)

    So, what do you want from me ? Should I copy 100 times :

    "I should not call it a recursive lock. I shall not invent new locking infra. I am a moron."
    "I should not call it a recursive lock. I shall not invent new locking infra. I am a moron."
    "I should not call it a recursive lock. I shall not invent new locking infra. I am a moron."
    "I should not call it a recursive lock. I shall not invent new locking infra. I am a moron."
    "I should not call it a recursive lock. I shall not invent new locking infra. I am a moron."
    "I should not call it a recursive lock. I shall not invent new locking infra. I am a moron."
    ...

    OK done

    Can we now proceed and continue ?

    Thank you

    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2009-04-22 19:01    [W:4.308 / U:0.112 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site