Messages in this thread |  | | Date | Tue, 4 Sep 2001 11:02:43 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | Re: [SOLVED + PATCH]: documented Oops running big-endian reiserfs on parisc architecture |
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On Tue, 4 Sep 2001, Ulrich Weigand wrote: [SNIPPED...]
> > If these instructions really *need* to be atomic, then reiserfs should > ensure they are performed on properly aligned data, or else there might > be subtle bugs even on Intel, because the operations will not actually > be atomic (even though they don't trap). >
Regardless of alignment, locked instructions in Intel machines are atomic. Any "hidden" read/modify/write operations are performed by the hardware, under the lock, preventing access by any other CPUs or DMA.
> If you say that reiserfs doesn't really need these operations to be > atomic because they run under other locks anyway, then they should not > be using atomic operations in the first place; this will only cause > unnecessary slowdown even on Intel. >
Agreed that there are many "atomic_t" types on some drivers, and "atomic" operations that don't need to be there. Unless a DMA operation is in progress, anything executing under a spin-lock doesn't need to be an "atomic" operation to make it, truly, atomic.
Cheers, Dick Johnson
Penguin : Linux version 2.4.1 on an i686 machine (799.53 BogoMips).
I was going to compile a list of innovations that could be attributed to Microsoft. Once I realized that Ctrl-Alt-Del was handled in the BIOS, I found that there aren't any.
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