Re: Using sched_clock for mmio-trace

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Sat, Feb 17, 2007 at 04:19:58PM +0100, Thomas Gleixner wrote:
> On Sat, 2007-02-17 at 15:56 +0100, Andi Kleen wrote:
> > > This is one of the reasons why we don't just use good old
> > > do_gettimeofday(), since it takes locks and can lead to lock recursion
> > > if parts of itself are probed.
> > 
> > do_gettimeofday doesn't take locks.
> > 
> > Only restriction is that you can't single step it with long 
> > pauses between instructions.
> 
> Err, it uses read side of xtime lock, so you can not call it from a
> place which write locks xtime lock.

Err, you can -- seqlocks never deadlock.

The only thing that doesn't work is to single step with long enough
pauses with interrupts on inbetween that the sequence numbers increase:
you get a livelock then.

-Andi
-
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]
  Powered by Linux