linux-toradex.git/kernel/dma/debug.c, branch v5.10-rc1

dma-mapping: move dma-debug.h to kernel/dma/

2020-10-06T05:07:05+00:00

Most of dma-debug.h is not required by anything outside of kernel/dma.
Move the four declarations needed by dma-mappin.h or dma-ops providers
into dma-mapping.h and dma-map-ops.h, and move the remainder of the
file to kernel/dma/debug.h.

Signed-off-by: Christoph Hellwig

dma-debug: convert comma to semicolon

2020-09-21T14:48:38+00:00

Replace a comma between expression statements by a semicolon.

Signed-off-by: Xu Wang 
Signed-off-by: Christoph Hellwig

dma-debug: remove most exports

2020-09-11T06:13:12+00:00

Now that the main dma mapping entry points are out of line most of the
symbols in dma-debug.c can only be called from built-in code.  Remove
the unused exports.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Robin Murphy

dma-debug: remove debug_dma_assert_idle() function

2020-08-14T22:22:43+00:00

This remoes the code from the COW path to call debug_dma_assert_idle(),
which was added many years ago.

Google shows that it hasn't caught anything in the 6+ years we've had it
apart from a false positive, and Hugh just noticed how it had a very
unfortunate spinlock serialization in the COW path.

He fixed that issue the previous commit (a85ffd59bd36: "dma-debug: fix
debug_dma_assert_idle(), use rcu_read_lock()"), but let's see if anybody
even notices when we remove this function entirely.

NOTE! We keep the dma tracking infrastructure that was added by the
commit that introduced it.  Partly to make it easier to resurrect this
debug code if we ever deside to, and partly because that tracking by pfn
and offset looks quite reasonable.

The problem with this debug code was simply that it was expensive and
didn't seem worth it, not that it was wrong per se.

Acked-by: Dan Williams 
Acked-by: Christoph Hellwig 
Signed-off-by: Linus Torvalds

dma-debug: fix debug_dma_assert_idle(), use rcu_read_lock()

2020-08-14T22:16:03+00:00

Since commit 2a9127fcf229 ("mm: rewrite wait_on_page_bit_common()
logic") improved unlock_page(), it has become more noticeable how
cow_user_page() in a kernel with CONFIG_DMA_API_DEBUG=y can create and
suffer from heavy contention on DMA debug's radix_lock in
debug_dma_assert_idle().

It is only doing a lookup: use rcu_read_lock() and rcu_read_unlock()
instead; though that does require the static ents[] to be moved
onstack...

...but, hold on, isn't that radix_tree_gang_lookup() and loop doing
quite the wrong thing: searching CACHELINES_PER_PAGE entries for an
exact match with the first cacheline of the page in question?
radix_tree_gang_lookup() is the right tool for the job, but we need
nothing more than to check the first entry it can find, reporting if
that falls anywhere within the page.

(Is RCU safe here? As safe as using the spinlock was. The entries are
never freed, so don't need to be freed by RCU. They may be reused, and
there is a faint chance of a race, with an offending entry reused while
printing its error info; but the spinlock did not prevent that either,
and I agree that it's not worth worrying about. ]

[ Side noe: this patch is a clear improvement to the status quo, but the
  next patch will be removing this debug function entirely.

  But just in case we decide we want to resurrect the debugging code
  some day, I'm first applying this improvement patch so that it doesn't
  get lost    - Linus ]

Fixes: 3b7a6418c749 ("dma debug: account for cachelines and read-only mappings in overlap tracking")
Signed-off-by: Hugh Dickins 
Acked-by: Dan Williams 
Acked-by: Christoph Hellwig 
Signed-off-by: Linus Torvalds

Merge tag 'docs-5.9' of git://git.lwn.net/linux

2020-08-05T05:47:54+00:00

Pull documentation updates from Jonathan Corbet:
 "It's been a busy cycle for documentation - hopefully the busiest for a
  while to come. Changes include:

   - Some new Chinese translations

   - Progress on the battle against double words words and non-HTTPS
     URLs

   - Some block-mq documentation

   - More RST conversions from Mauro. At this point, that task is
     essentially complete, so we shouldn't see this kind of churn again
     for a while. Unless we decide to switch to asciidoc or
     something...:)

   - Lots of typo fixes, warning fixes, and more"

* tag 'docs-5.9' of git://git.lwn.net/linux: (195 commits)
  scripts/kernel-doc: optionally treat warnings as errors
  docs: ia64: correct typo
  mailmap: add entry for 
  doc/zh_CN: add cpu-load Chinese version
  Documentation/admin-guide: tainted-kernels: fix spelling mistake
  MAINTAINERS: adjust kprobes.rst entry to new location
  devices.txt: document rfkill allocation
  PCI: correct flag name
  docs: filesystems: vfs: correct flag name
  docs: filesystems: vfs: correct sync_mode flag names
  docs: path-lookup: markup fixes for emphasis
  docs: path-lookup: more markup fixes
  docs: path-lookup: fix HTML entity mojibake
  CREDITS: Replace HTTP links with HTTPS ones
  docs: process: Add an example for creating a fixes tag
  doc/zh_CN: add Chinese translation prefer section
  doc/zh_CN: add clearing-warn-once Chinese version
  doc/zh_CN: add admin-guide index
  doc:it_IT: process: coding-style.rst: Correct __maybe_unused compiler label
  futex: MAINTAINERS: Re-add selftests directory
  ...

Merge tag 'dma-mapping-5.9' of git://git.infradead.org/users/hch/dma-mapping

2020-08-05T00:29:57+00:00

Pull dma-mapping updates from Christoph Hellwig:

 - make support for dma_ops optional

 - move more code out of line

 - add generic support for a dma_ops bypass mode

 - misc cleanups

* tag 'dma-mapping-5.9' of git://git.infradead.org/users/hch/dma-mapping:
  dma-contiguous: cleanup dma_alloc_contiguous
  dma-debug: use named initializers for dir2name
  powerpc: use the generic dma_ops_bypass mode
  dma-mapping: add a dma_ops_bypass flag to struct device
  dma-mapping: make support for dma ops optional
  dma-mapping: inline the fast path dma-direct calls
  dma-mapping: move the remaining DMA API calls out of line

dma-debug: use named initializers for dir2name

2020-07-19T07:31:13+00:00

Make dir2name a little more readable and maintainable by using
named initializers.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Robin Murphy

treewide: Remove uninitialized_var() usage

2020-07-16T19:35:15+00:00

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.

In preparation for removing[2] the[3] macro[4], remove all remaining
needless uses with the following script:

git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \
	xargs perl -pi -e \
		's/\buninitialized_var\(([^\)]+)\)/\1/g;
		 s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;'

drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid
pathological white-space.

No outstanding warnings were found building allmodconfig with GCC 9.3.0
for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64,
alpha, and m68k.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Reviewed-by: Leon Romanovsky  # drivers/infiniband and mlx4/mlx5
Acked-by: Jason Gunthorpe  # IB
Acked-by: Kalle Valo  # wireless drivers
Reviewed-by: Chao Yu  # erofs
Signed-off-by: Kees Cook

docs: fix references for DMA*.txt files

2020-06-26T16:01:32+00:00

As we moved those files to core-api, fix references to point
to their newer locations.

Signed-off-by: Mauro Carvalho Chehab 
Link: https://lore.kernel.org/r/37b2fd159fbc7655dbf33b3eb1215396a25f6344.1592895969.git.mchehab+huawei@kernel.org
Signed-off-by: Jonathan Corbet