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Date: Sun, 7 Jun 2009 10:22:00 +0200 From: Torsten Kaiser <just.for.lkml@...glemail.com> To: Ingo Molnar <mingo@...e.hu> Cc: Joerg Roedel <joerg.roedel@....com>, FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>, Linus Torvalds <torvalds@...ux-foundation.org>, lethal@...ux-sh.org, hancockrwd@...il.com, jens.axboe@...cle.com, bharrosh@...asas.com, linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org Subject: Re: [PATCH] dma-debug: disable DMA_API_DEBUG for now On Sun, Jun 7, 2009 at 10:13 AM, Ingo Molnar <mingo@...e.hu> wrote: > * Joerg Roedel <joerg.roedel@....com> wrote: >> But its up to Linus/Ingo to decide if it can be accepted at this >> very late point in the cycle. Since dma-debug is new with 2.6.30 >> it will at least not introduce any regression. [...] > > I think it's too late for v2.6.30 to do any of the changes - and the > DMA debug facility is off by default. > > Also, i think such DMA patterns, while 'allowed' can be quite > dangerous as its such a rare usage combination really. AIO and DIO > are crazy to begin with, mixing AIO and DIO for the same buffer is > madness square two. (It can result in 3 agents for the same memory > address: CPU, dma1 and dma2. How many interesting chipset erratums > could there be related to such scenarios?) I think in my case the cause is somewhat simpler: RAID1 My root filesystem is on a RAID1 that consists of two disks, both connected to the sata_sil24 controller. So it is only natural for the md driver to issue two dma read requests for the same address: one for each drive. Torsten -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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