Messages in this thread | | | Date | Sun, 18 Feb 2007 18:20:43 +0100 | From | Andi Kleen <> | Subject | Re: Using sched_clock for mmio-trace |
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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.
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