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Robin Murphy d27fb99f62 dma-mapping: relax warning for per-device areas
The reasons why dma_free_attrs() should not be called from IRQ context
are not necessarily obvious and somewhat buried in the development
history, so let's start by documenting the warning itself to help anyone
who does happen to hit it and wonder what the deal is.

However, this check turns out to be slightly over-restrictive for the
way that per-device memory has been spliced into the general API, since
for that case we know that dma_declare_coherent_memory() has created an
appropriate CPU mapping for the entire area and nothing dynamic should
be happening. Given that the usage model for per-device memory is often
more akin to streaming DMA than 'real' coherent DMA (e.g. allocating and
freeing space to copy short-lived packets in and out), it is also
somewhat more reasonable for those operations to happen in IRQ handlers
for such devices.

Therefore, let's move the irqs_disabled() check down past the per-device
area hook, so that that gets a chance to resolve the request before we
reach definite "you're doing it wrong" territory.

Reported-by: Fredrik Noring <noring@nocrew.org>
Tested-by: Fredrik Noring <noring@nocrew.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
2018-07-25 13:32:58 +02:00
arch alpha: fix osf_wait4() breakage 2018-07-22 11:51:30 -07:00
block
certs
crypto
Documentation - Fix DM writecache target to allow an optional offset to the start of 2018-07-20 14:24:17 -07:00
drivers NVMe fixes for 4.18-rc6: 2018-07-22 13:21:45 -07:00
firmware
fs Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2018-07-22 12:04:51 -07:00
include dma-mapping: relax warning for per-device areas 2018-07-25 13:32:58 +02:00
init
ipc
kernel Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-07-21 17:21:34 -07:00
lib Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-07-21 16:52:08 -07:00
LICENSES
mm mm: make vm_area_alloc() initialize core fields 2018-07-21 15:24:03 -07:00
net
samples
scripts
security
sound
tools Merge branch 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-07-21 16:52:08 -07:00
usr
virt
.clang-format
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore
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COPYING
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MAINTAINERS MAINTAINERS: Peter has moved 2018-07-21 12:50:46 -07:00
Makefile Linux 4.18-rc6 2018-07-22 14:12:20 -07:00
README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.