On Thu, Sep 21, 2006 at 09:56:33AM +0200, Ingo Molnar wrote:
> * Bill Huey <[email protected]> wrote:
>
> > [...] If the upstream kernel used RCU function in a task allocation or
> > task struct reading in the first place then call_rcu() would be a
> > clear choice. However, I didn't see it used in that way (I could be
> > wrong) [...]
>
> it was RCU-ified briefly but then it was further improved to direct
> freeing, because upstream _can_ free it directly.
Unfortunately, this is a problem with -rt patch and the lock ordering
in this system when you have to call a memory allocator within an atomic
critical section. I fully accept this as part of what goes into making a
kernel preemptive and I'm ok with it. Not many folks know about the
special case locking rules in the -rt kernel so this might be new to
various folks.
If you're looking for validation of this technique from me and an ego
stroking, then you have it from me. :)
Fortunately, it's in a non-critical place so this should *not* be too
much of a problem, but I've already encountered oddies trying to
allocate a pool of entities for populating a free list under an atomic
critical section of some sort for some code I've been writing. This is
a significant problem with kernel coding in -rt, but I can't say what
the general solution is other than making the memory allocators
non-preemptible by reverting the locks back to raw spinlocks, etc...
using lock-break, who knows. I'm ok with the current scenario, but this
could eventually be a larger problem.
bill
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
