Messages in this thread | | | Date | Thu, 25 Jul 2002 09:54:25 +0200 | From | Marcin Dalecki <> | Subject | Re: Safety of IRQ during i/o |
| |
Bartlomiej Zolnierkiewicz wrote: > On Wed, 24 Jul 2002, Pete Zaitcev wrote: > > >>>[...] >>>I would think that this would be safe when using DMA, and likely to be >>>safe for PIO and more recent chipsets, but I wouldn't want to actually >>>tell anyone that. >> >>A little story from OLS. I have a 486/75 laptop, which can only >>do PIO. It always was losing characters evern on 9600 baud on its >>serial port, and I thought it was simply broken for five years. > > > :-) > > >>A guy who did a security talk showed me that doing hdparm -u >>fixes the problem. Apparently, the lappy has a non-buffering UART. >> >>So, it seems that hdparm -u is a very useful thing for obsotele >>boxes. If you do DMA, you probably do not care. > > > Yup, for PIO unmask (if possible) is a must.
It's even for DMA a good thing, since the IRQ handler in question can reenter the RQ handler. The invention of the not unmasking behaviour in Linux is the result of some not entierly ATA-2 compliant devices long long time ago gone. Basically XT disks on PC. They did have the habbit of splewing IRQs too early for command ACK.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |