Re: FS Corruption in 2.1.109 (fwd)

Mark Lord (
Thu, 30 Jul 1998 18:43:53 -0400

Richard B. Johnson wrote:
> Now we have UDMA (Ugly DMA). Once the chip is programmed, the
> CPU is available for other uses while the DMA completes. Looking
> at the sources, I see that the CPU is really just polling for

No, it is not polling for completion.
Completion is signaled by a hardware interrupt,
and the CPU is elsewhere until that happens.

> completion (yes, the interrupts are enabled so something else could
> use the CPU). Any problem with locking, that could prevent these
> I/O operations from being atomic can cause problems.
> Since enabling interrupts during the PIO operation was a bad_thing(tm),

On only a couple of systems (other than cmd640 and rz1000 systems).
It is a Good Thing(tm) on all others. The default is "off" for safety.

The (ex-)Linux IDE guy

- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to Please read the FAQ at