Re: CURRENT + amd64 + user-ppp = panic

From: Victor Snezhko (snezhko_at_indorsoft.ru)
Date: 11/09/05

  • Next message: Marcin Jessa: "Re: Generic Kernel API" 
    To: Mark Tinguely <tinguely@casselton.net>
Date: Wed, 09 Nov 2005 14:25:37 +0600

    Mark Tinguely <tinguely@casselton.net> writes:

    > This is great, you caught the kernel trashing a callout entry
    > in uma_dbg.

    Hmm, not so fast...

    Look at the list output:

    103 if ((u_int32_t)c == uma_junk) {
    104 kdb_enter("trash_dtor: uma_junk found in a "\
    105 "callwheel element");

    By the moment when I start traversing callwheel, it is already
    corrupted! (Or maybe modified by someone who doesn't hold the
    callout_lock)

    > I cannot figure out how #14 linked the function sorecieved() to
    > the inline function uma_zfree(). (thinking as I am typing) Could
    > someone changed the recieve function call for this socket?

    Maybe inline function introduces this mess?

    > In my opinion, you can remove the callout_check_callwheel function
    > and calls.

    Agreed, I just wanted to demonstrate that things are not so simple.

    > You want to always catch it before it corrupts, and that
    > is done in the uma_dbg.

    Unfortunately, uma_dbg catches already corrupted callwheel (or
    not catches anything at all, in this case ppp works)

    > Once you catch the corruption, we know it will panic in the near
    > future, unless we are in the debugger long enough, for the timer to
    > expire and be removed.

    Hmm, looks like it's really so. This needs additional checking.

    > I would completely delete the compile directory and "config" and
    > do a fresh make.

    This is exactly what I have done before submitting my report. Because
    I cvsdown'ed to 2005.10.21.16.30.00 to be independent of recent
    changes that would mess up something. I also tested on fresh current
    on Saturday or Sunday - backtrace was similar - may be different lines
    or something. 

    -- 
WBR, Victor V. Snezhko
EMail: snezhko@indorsoft.ru
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