From: Christoph Hellwig <hch@infradead.org>
To: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
Cc: james.bottomley@hansenpartnership.com,
martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
linuxppc-dev@lists.ozlabs.org, brking@linux.vnet.ibm.com,
stable@vger.kernel.org
Subject: Re: [PATCH] ibmvscsi: use GFP_ATOMIC with dma_alloc_coherent in map_sg_data
Date: Thu, 10 Jan 2019 07:07:03 -0800 [thread overview]
Message-ID: <20190110150703.GA26696@infradead.org> (raw)
In-Reply-To: <1547089136-20264-1-git-send-email-tyreld@linux.vnet.ibm.com>
On Wed, Jan 09, 2019 at 06:58:56PM -0800, Tyrel Datwyler wrote:
> While mapping DMA for scatter list when a scsi command is queued the
> existing call to dma_alloc_coherent() in our map_sg_data() function
> passes zero for the gfp_flags parameter. We are most definitly in atomic
> context at this point as queue_command() is called in softirq context
> and further we have a spinlock holding the scsi host lock.
>
> Fix this by passing GFP_ATOMIC to dma_alloc_coherent() to prevent any
> sort of sleeping in atomic context deadlock.
This is a pretty clear sign you should not be using dma_alloc_coherent
to start with. GFP_ATOMIC support in many of the implementations either
doesn't work at all or is severly constrained. Given that the
descriptor is written by the OS and read by the hardware exactly once
there is no point in having the coherent mapping to start with.
next prev parent reply other threads:[~2019-01-10 15:07 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-10 2:58 [PATCH] ibmvscsi: use GFP_ATOMIC with dma_alloc_coherent in map_sg_data Tyrel Datwyler
2019-01-10 14:56 ` Brian King
2019-01-10 15:07 ` Christoph Hellwig [this message]
2019-01-10 20:11 ` Tyrel Datwyler
2019-01-11 18:24 ` Christoph Hellwig
2019-01-10 23:15 ` Tyrel Datwyler
2019-01-11 18:27 ` Christoph Hellwig
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20190110150703.GA26696@infradead.org \
--to=hch@infradead.org \
--cc=brking@linux.vnet.ibm.com \
--cc=james.bottomley@hansenpartnership.com \
--cc=linux-scsi@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=martin.petersen@oracle.com \
--cc=stable@vger.kernel.org \
--cc=tyreld@linux.vnet.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).