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    SubjectRe: 2.6.13-rc6-rt9

    * Steven Rostedt <rostedt@goodmis.org> wrote:

    > On Tue, 2005-08-23 at 14:36 +0200, Ingo Molnar wrote:
    > > * Steven Rostedt <rostedt@goodmis.org> wrote:
    > >
    > > > Ingo, can't you get rt.c to be more confusing. I mean it is too
    > > > simple. We need to add a few more underscores here and there :-)
    > > > Seriously, that rt.c is mind boggling. It was nice before, now it is
    > > > just screaming for a cleanup (come now, do we really need the four
    > > > underscores?). Same with latency.c.
    > >
    > > i agree that it's ugly, but some of that ugliness is to achieve the
    > > 7-instructions fail-through codepath for the common acquire (and
    > > release) codepath:
    > >
    > > c03a5320 <__down_mutex>:
    > > c03a5320: 89 c1 mov %eax,%ecx
    > > c03a5322: 8b 15 08 76 3a c0 mov 0xc03a7608,%edx
    > > c03a5328: 31 c0 xor %eax,%eax
    > > c03a532a: 0f b1 51 14 cmpxchg %edx,0x14(%ecx)
    > > c03a532e: 85 c0 test %eax,%eax
    > > c03a5330: 75 01 jne c03a5333 <__down_mutex+0x13>
    > > c03a5332: c3 ret
    > >
    >
    > Impressive!
    >
    > > that's how much it takes to acquire an RT lock, and i worked hard to get
    > > there. As long as the fastpath is kept this tight, feel free to do
    > > cleanups. But i really want to avoid having to write mutex_down/up in
    > > assembly for 24 architectures ...
    >
    > Warning! I'm hacking hard to get rid of the global pi_lock, and I'm not
    > worrying now about efficiency. I figure that if I can get it to work,
    > then we can speed it up afterwards. Since it's complex enough keeping
    > all the locks straight, I just want it to work without deadlocking.
    >
    > Once I get it to work, I'll let you figure out how get it back down to
    > 7-instructions :-)

    yeah. It can always be done after the fact - the basics wont change.
    (Note that the above disassembly is for UP, on SMP the fastpath is
    longer and around 10-15 instructions.)

    Ingo
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