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<title>pm24.git/include, branch v5.1-rc4</title>
<subtitle>Unnamed repository; edit this file 'description' to name the repository.</subtitle>
<id>https://git.kobert.dev/pm24.git/atom/include?h=v5.1-rc4</id>
<link rel='self' href='https://git.kobert.dev/pm24.git/atom/include?h=v5.1-rc4'/>
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<updated>2019-04-07T23:46:17Z</updated>
<entry>
<title>Merge tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc</title>
<updated>2019-04-07T23:46:17Z</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2019-04-07T23:46:17Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=d8491223bc243b960ee1c4a8aa5219eca0d69acf'/>
<id>urn:sha1:d8491223bc243b960ee1c4a8aa5219eca0d69acf</id>
<content type='text'>
Pull ARM SoC fixes from Olof Johansson:
 "A collection of fixes from the last few weeks. Most of them are
  smaller tweaks and fixes to DT and hardware descriptions for boards.
  Some of the more significant ones are:

   - eMMC and RGMII stability tweaks for rk3288

   - DDC fixes for Rock PI 4

   - Audio fixes for two TI am335x eval boards

   - D_CAN clock fix for am335x

   - Compilation fixes for clang

   - !HOTPLUG_CPU compilation fix for one of the new platforms this
     release (milbeaut)

   - A revert of a gpio fix for nomadik that instead was fixed in the
     gpio subsystem

   - Whitespace fix for the DT JSON schema (no tabs allowed)"

* tag 'armsoc-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: (25 commits)
  ARM: milbeaut: fix build with !CONFIG_HOTPLUG_CPU
  ARM: iop: don't use using 64-bit DMA masks
  ARM: orion: don't use using 64-bit DMA masks
  Revert "ARM: dts: nomadik: Fix polarity of SPI CS"
  dt-bindings: cpu: Fix JSON schema
  arm/mach-at91/pm : fix possible object reference leak
  ARM: dts: at91: Fix typo in ISC_D0 on PC9
  ARM: dts: Fix dcan clkctrl clock for am3
  reset: meson-audio-arb: Fix missing .owner setting of reset_controller_dev
  dt-bindings: reset: meson-g12a: Add missing USB2 PHY resets
  ARM: dts: rockchip: Remove #address/#size-cells from rk3288-veyron gpio-keys
  ARM: dts: rockchip: Remove #address/#size-cells from rk3288 mipi_dsi
  ARM: dts: rockchip: Fix gpu opp node names for rk3288
  ARM: dts: am335x-evmsk: Correct the regulators for the audio codec
  ARM: dts: am335x-evm: Correct the regulators for the audio codec
  ARM: OMAP2+: add missing of_node_put after of_device_is_available
  ARM: OMAP1: ams-delta: Fix broken GPIO ID allocation
  arm64: dts: stratix10: add the sysmgr-syscon property from the gmac's
  arm64: dts: rockchip: fix rk3328 sdmmc0 write errors
  arm64: dts: rockchip: fix rk3328 rgmii high tx error rate
  ...
</content>
</entry>
<entry>
<title>Merge tag 'reset-fixes-for-v5.1' of git://git.pengutronix.de/pza/linux into arm/fixes</title>
<updated>2019-04-07T22:14:00Z</updated>
<author>
<name>Olof Johansson</name>
<email>olof@lixom.net</email>
</author>
<published>2019-04-07T22:14:00Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=57683e452b73d1f4f7fbe4627196139b9772c51a'/>
<id>urn:sha1:57683e452b73d1f4f7fbe4627196139b9772c51a</id>
<content type='text'>
Reset controller fixes for v5.1

This tag adds missing USB PHY reset lines to the Meson G12A reset
controller header and fixes the Meson Audio ARB driver to prevent
module unloading while it is in use.

* tag 'reset-fixes-for-v5.1' of git://git.pengutronix.de/pza/linux:
  reset: meson-audio-arb: Fix missing .owner setting of reset_controller_dev
  dt-bindings: reset: meson-g12a: Add missing USB2 PHY resets

Signed-off-by: Olof Johansson &lt;olof@lixom.net&gt;
</content>
</entry>
<entry>
<title>fs: stream_open - opener for stream-like files so that read and write can run simultaneously without deadlock</title>
<updated>2019-04-06T17:01:55Z</updated>
<author>
<name>Kirill Smelkov</name>
<email>kirr@nexedi.com</email>
</author>
<published>2019-03-26T22:20:43Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=10dce8af34226d90fa56746a934f8da5dcdba3df'/>
<id>urn:sha1:10dce8af34226d90fa56746a934f8da5dcdba3df</id>
<content type='text'>
Commit 9c225f2655e3 ("vfs: atomic f_pos accesses as per POSIX") added
locking for file.f_pos access and in particular made concurrent read and
write not possible - now both those functions take f_pos lock for the
whole run, and so if e.g. a read is blocked waiting for data, write will
deadlock waiting for that read to complete.

This caused regression for stream-like files where previously read and
write could run simultaneously, but after that patch could not do so
anymore. See e.g. commit 581d21a2d02a ("xenbus: fix deadlock on writes
to /proc/xen/xenbus") which fixes such regression for particular case of
/proc/xen/xenbus.

The patch that added f_pos lock in 2014 did so to guarantee POSIX thread
safety for read/write/lseek and added the locking to file descriptors of
all regular files. In 2014 that thread-safety problem was not new as it
was already discussed earlier in 2006.

However even though 2006'th version of Linus's patch was adding f_pos
locking "only for files that are marked seekable with FMODE_LSEEK (thus
avoiding the stream-like objects like pipes and sockets)", the 2014
version - the one that actually made it into the tree as 9c225f2655e3 -
is doing so irregardless of whether a file is seekable or not.

See

    https://lore.kernel.org/lkml/53022DB1.4070805@gmail.com/
    https://lwn.net/Articles/180387
    https://lwn.net/Articles/180396

for historic context.

The reason that it did so is, probably, that there are many files that
are marked non-seekable, but e.g. their read implementation actually
depends on knowing current position to correctly handle the read. Some
examples:

	kernel/power/user.c		snapshot_read
	fs/debugfs/file.c		u32_array_read
	fs/fuse/control.c		fuse_conn_waiting_read + ...
	drivers/hwmon/asus_atk0110.c	atk_debugfs_ggrp_read
	arch/s390/hypfs/inode.c		hypfs_read_iter
	...

Despite that, many nonseekable_open users implement read and write with
pure stream semantics - they don't depend on passed ppos at all. And for
those cases where read could wait for something inside, it creates a
situation similar to xenbus - the write could be never made to go until
read is done, and read is waiting for some, potentially external, event,
for potentially unbounded time -&gt; deadlock.

Besides xenbus, there are 14 such places in the kernel that I've found
with semantic patch (see below):

	drivers/xen/evtchn.c:667:8-24: ERROR: evtchn_fops: .read() can deadlock .write()
	drivers/isdn/capi/capi.c:963:8-24: ERROR: capi_fops: .read() can deadlock .write()
	drivers/input/evdev.c:527:1-17: ERROR: evdev_fops: .read() can deadlock .write()
	drivers/char/pcmcia/cm4000_cs.c:1685:7-23: ERROR: cm4000_fops: .read() can deadlock .write()
	net/rfkill/core.c:1146:8-24: ERROR: rfkill_fops: .read() can deadlock .write()
	drivers/s390/char/fs3270.c:488:1-17: ERROR: fs3270_fops: .read() can deadlock .write()
	drivers/usb/misc/ldusb.c:310:1-17: ERROR: ld_usb_fops: .read() can deadlock .write()
	drivers/hid/uhid.c:635:1-17: ERROR: uhid_fops: .read() can deadlock .write()
	net/batman-adv/icmp_socket.c:80:1-17: ERROR: batadv_fops: .read() can deadlock .write()
	drivers/media/rc/lirc_dev.c:198:1-17: ERROR: lirc_fops: .read() can deadlock .write()
	drivers/leds/uleds.c:77:1-17: ERROR: uleds_fops: .read() can deadlock .write()
	drivers/input/misc/uinput.c:400:1-17: ERROR: uinput_fops: .read() can deadlock .write()
	drivers/infiniband/core/user_mad.c:985:7-23: ERROR: umad_fops: .read() can deadlock .write()
	drivers/gnss/core.c:45:1-17: ERROR: gnss_fops: .read() can deadlock .write()

In addition to the cases above another regression caused by f_pos
locking is that now FUSE filesystems that implement open with
FOPEN_NONSEEKABLE flag, can no longer implement bidirectional
stream-like files - for the same reason as above e.g. read can deadlock
write locking on file.f_pos in the kernel.

FUSE's FOPEN_NONSEEKABLE was added in 2008 in a7c1b990f715 ("fuse:
implement nonseekable open") to support OSSPD. OSSPD implements /dev/dsp
in userspace with FOPEN_NONSEEKABLE flag, with corresponding read and
write routines not depending on current position at all, and with both
read and write being potentially blocking operations:

See

    https://github.com/libfuse/osspd
    https://lwn.net/Articles/308445

    https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1406
    https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1438-L1477
    https://github.com/libfuse/osspd/blob/14a9cff0/osspd.c#L1479-L1510

Corresponding libfuse example/test also describes FOPEN_NONSEEKABLE as
"somewhat pipe-like files ..." with read handler not using offset.
However that test implements only read without write and cannot exercise
the deadlock scenario:

    https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L124-L131
    https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L146-L163
    https://github.com/libfuse/libfuse/blob/fuse-3.4.2-3-ga1bff7d/example/poll.c#L209-L216

I've actually hit the read vs write deadlock for real while implementing
my FUSE filesystem where there is /head/watch file, for which open
creates separate bidirectional socket-like stream in between filesystem
and its user with both read and write being later performed
simultaneously. And there it is semantically not easy to split the
stream into two separate read-only and write-only channels:

    https://lab.nexedi.com/kirr/wendelin.core/blob/f13aa600/wcfs/wcfs.go#L88-169

Let's fix this regression. The plan is:

1. We can't change nonseekable_open to include &amp;~FMODE_ATOMIC_POS -
   doing so would break many in-kernel nonseekable_open users which
   actually use ppos in read/write handlers.

2. Add stream_open() to kernel to open stream-like non-seekable file
   descriptors. Read and write on such file descriptors would never use
   nor change ppos. And with that property on stream-like files read and
   write will be running without taking f_pos lock - i.e. read and write
   could be running simultaneously.

3. With semantic patch search and convert to stream_open all in-kernel
   nonseekable_open users for which read and write actually do not
   depend on ppos and where there is no other methods in file_operations
   which assume @offset access.

4. Add FOPEN_STREAM to fs/fuse/ and open in-kernel file-descriptors via
   steam_open if that bit is present in filesystem open reply.

   It was tempting to change fs/fuse/ open handler to use stream_open
   instead of nonseekable_open on just FOPEN_NONSEEKABLE flags, but
   grepping through Debian codesearch shows users of FOPEN_NONSEEKABLE,
   and in particular GVFS which actually uses offset in its read and
   write handlers

	https://codesearch.debian.net/search?q=-%3Enonseekable+%3D
	https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1080
	https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1247-1346
	https://gitlab.gnome.org/GNOME/gvfs/blob/1.40.0-6-gcbc54396/client/gvfsfusedaemon.c#L1399-1481

   so if we would do such a change it will break a real user.

5. Add stream_open and FOPEN_STREAM handling to stable kernels starting
   from v3.14+ (the kernel where 9c225f2655 first appeared).

   This will allow to patch OSSPD and other FUSE filesystems that
   provide stream-like files to return FOPEN_STREAM | FOPEN_NONSEEKABLE
   in their open handler and this way avoid the deadlock on all kernel
   versions. This should work because fs/fuse/ ignores unknown open
   flags returned from a filesystem and so passing FOPEN_STREAM to a
   kernel that is not aware of this flag cannot hurt. In turn the kernel
   that is not aware of FOPEN_STREAM will be &lt; v3.14 where just
   FOPEN_NONSEEKABLE is sufficient to implement streams without read vs
   write deadlock.

This patch adds stream_open, converts /proc/xen/xenbus to it and adds
semantic patch to automatically locate in-kernel places that are either
required to be converted due to read vs write deadlock, or that are just
safe to be converted because read and write do not use ppos and there
are no other funky methods in file_operations.

Regarding semantic patch I've verified each generated change manually -
that it is correct to convert - and each other nonseekable_open instance
left - that it is either not correct to convert there, or that it is not
converted due to current stream_open.cocci limitations.

The script also does not convert files that should be valid to convert,
but that currently have .llseek = noop_llseek or generic_file_llseek for
unknown reason despite file being opened with nonseekable_open (e.g.
drivers/input/mousedev.c)

Cc: Michael Kerrisk &lt;mtk.manpages@gmail.com&gt;
Cc: Yongzhi Pan &lt;panyongzhi@gmail.com&gt;
Cc: Jonathan Corbet &lt;corbet@lwn.net&gt;
Cc: David Vrabel &lt;david.vrabel@citrix.com&gt;
Cc: Juergen Gross &lt;jgross@suse.com&gt;
Cc: Miklos Szeredi &lt;miklos@szeredi.hu&gt;
Cc: Tejun Heo &lt;tj@kernel.org&gt;
Cc: Kirill Tkhai &lt;ktkhai@virtuozzo.com&gt;
Cc: Arnd Bergmann &lt;arnd@arndb.de&gt;
Cc: Christoph Hellwig &lt;hch@lst.de&gt;
Cc: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Cc: Julia Lawall &lt;Julia.Lawall@lip6.fr&gt;
Cc: Nikolaus Rath &lt;Nikolaus@rath.org&gt;
Cc: Han-Wen Nienhuys &lt;hanwen@google.com&gt;
Signed-off-by: Kirill Smelkov &lt;kirr@nexedi.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>Merge branch 'akpm' (patches from Andrew)</title>
<updated>2019-04-06T03:08:55Z</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2019-04-06T03:08:55Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=f654f0fc0bd3f1b0ec76e654bf1cc21f33382241'/>
<id>urn:sha1:f654f0fc0bd3f1b0ec76e654bf1cc21f33382241</id>
<content type='text'>
Merge misc fixes from Andrew Morton:
 "14 fixes"

* emailed patches from Andrew Morton &lt;akpm@linux-foundation.org&gt;:
  kernel/sysctl.c: fix out-of-bounds access when setting file-max
  mm/util.c: fix strndup_user() comment
  sh: fix multiple function definition build errors
  MAINTAINERS: add maintainer and replacing reviewer ARM/NUVOTON NPCM
  MAINTAINERS: fix bad pattern in ARM/NUVOTON NPCM
  mm: writeback: use exact memcg dirty counts
  psi: clarify the units used in pressure files
  mm/huge_memory.c: fix modifying of page protection by insert_pfn_pmd()
  hugetlbfs: fix memory leak for resv_map
  mm: fix vm_fault_t cast in VM_FAULT_GET_HINDEX()
  lib/lzo: fix bugs for very short or empty input
  include/linux/bitrev.h: fix constant bitrev
  kmemleak: powerpc: skip scanning holes in the .bss section
  lib/string.c: implement a basic bcmp
</content>
</entry>
<entry>
<title>mm: writeback: use exact memcg dirty counts</title>
<updated>2019-04-06T02:02:31Z</updated>
<author>
<name>Greg Thelen</name>
<email>gthelen@google.com</email>
</author>
<published>2019-04-06T01:39:18Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=0b3d6e6f2dd0a7b697b1aa8c167265908940624b'/>
<id>urn:sha1:0b3d6e6f2dd0a7b697b1aa8c167265908940624b</id>
<content type='text'>
Since commit a983b5ebee57 ("mm: memcontrol: fix excessive complexity in
memory.stat reporting") memcg dirty and writeback counters are managed
as:

 1) per-memcg per-cpu values in range of [-32..32]

 2) per-memcg atomic counter

When a per-cpu counter cannot fit in [-32..32] it's flushed to the
atomic.  Stat readers only check the atomic.  Thus readers such as
balance_dirty_pages() may see a nontrivial error margin: 32 pages per
cpu.

Assuming 100 cpus:
   4k x86 page_size:  13 MiB error per memcg
  64k ppc page_size: 200 MiB error per memcg

Considering that dirty+writeback are used together for some decisions the
errors double.

This inaccuracy can lead to undeserved oom kills.  One nasty case is
when all per-cpu counters hold positive values offsetting an atomic
negative value (i.e.  per_cpu[*]=32, atomic=n_cpu*-32).
balance_dirty_pages() only consults the atomic and does not consider
throttling the next n_cpu*32 dirty pages.  If the file_lru is in the
13..200 MiB range then there's absolutely no dirty throttling, which
burdens vmscan with only dirty+writeback pages thus resorting to oom
kill.

It could be argued that tiny containers are not supported, but it's more
subtle.  It's the amount the space available for file lru that matters.
If a container has memory.max-200MiB of non reclaimable memory, then it
will also suffer such oom kills on a 100 cpu machine.

The following test reliably ooms without this patch.  This patch avoids
oom kills.

  $ cat test
  mount -t cgroup2 none /dev/cgroup
  cd /dev/cgroup
  echo +io +memory &gt; cgroup.subtree_control
  mkdir test
  cd test
  echo 10M &gt; memory.max
  (echo $BASHPID &gt; cgroup.procs &amp;&amp; exec /memcg-writeback-stress /foo)
  (echo $BASHPID &gt; cgroup.procs &amp;&amp; exec dd if=/dev/zero of=/foo bs=2M count=100)

  $ cat memcg-writeback-stress.c
  /*
   * Dirty pages from all but one cpu.
   * Clean pages from the non dirtying cpu.
   * This is to stress per cpu counter imbalance.
   * On a 100 cpu machine:
   * - per memcg per cpu dirty count is 32 pages for each of 99 cpus
   * - per memcg atomic is -99*32 pages
   * - thus the complete dirty limit: sum of all counters 0
   * - balance_dirty_pages() only sees atomic count -99*32 pages, which
   *   it max()s to 0.
   * - So a workload can dirty -99*32 pages before balance_dirty_pages()
   *   cares.
   */
  #define _GNU_SOURCE
  #include &lt;err.h&gt;
  #include &lt;fcntl.h&gt;
  #include &lt;sched.h&gt;
  #include &lt;stdlib.h&gt;
  #include &lt;stdio.h&gt;
  #include &lt;sys/stat.h&gt;
  #include &lt;sys/sysinfo.h&gt;
  #include &lt;sys/types.h&gt;
  #include &lt;unistd.h&gt;

  static char *buf;
  static int bufSize;

  static void set_affinity(int cpu)
  {
  	cpu_set_t affinity;

  	CPU_ZERO(&amp;affinity);
  	CPU_SET(cpu, &amp;affinity);
  	if (sched_setaffinity(0, sizeof(affinity), &amp;affinity))
  		err(1, "sched_setaffinity");
  }

  static void dirty_on(int output_fd, int cpu)
  {
  	int i, wrote;

  	set_affinity(cpu);
  	for (i = 0; i &lt; 32; i++) {
  		for (wrote = 0; wrote &lt; bufSize; ) {
  			int ret = write(output_fd, buf+wrote, bufSize-wrote);
  			if (ret == -1)
  				err(1, "write");
  			wrote += ret;
  		}
  	}
  }

  int main(int argc, char **argv)
  {
  	int cpu, flush_cpu = 1, output_fd;
  	const char *output;

  	if (argc != 2)
  		errx(1, "usage: output_file");

  	output = argv[1];
  	bufSize = getpagesize();
  	buf = malloc(getpagesize());
  	if (buf == NULL)
  		errx(1, "malloc failed");

  	output_fd = open(output, O_CREAT|O_RDWR);
  	if (output_fd == -1)
  		err(1, "open(%s)", output);

  	for (cpu = 0; cpu &lt; get_nprocs(); cpu++) {
  		if (cpu != flush_cpu)
  			dirty_on(output_fd, cpu);
  	}

  	set_affinity(flush_cpu);
  	if (fsync(output_fd))
  		err(1, "fsync(%s)", output);
  	if (close(output_fd))
  		err(1, "close(%s)", output);
  	free(buf);
  }

Make balance_dirty_pages() and wb_over_bg_thresh() work harder to
collect exact per memcg counters.  This avoids the aforementioned oom
kills.

This does not affect the overhead of memory.stat, which still reads the
single atomic counter.

Why not use percpu_counter? memcg already handles cpus going offline, so
no need for that overhead from percpu_counter.  And the percpu_counter
spinlocks are more heavyweight than is required.

It probably also makes sense to use exact dirty and writeback counters
in memcg oom reports.  But that is saved for later.

Link: http://lkml.kernel.org/r/20190329174609.164344-1-gthelen@google.com
Signed-off-by: Greg Thelen &lt;gthelen@google.com&gt;
Reviewed-by: Roman Gushchin &lt;guro@fb.com&gt;
Acked-by: Johannes Weiner &lt;hannes@cmpxchg.org&gt;
Cc: Michal Hocko &lt;mhocko@kernel.org&gt;
Cc: Vladimir Davydov &lt;vdavydov.dev@gmail.com&gt;
Cc: Tejun Heo &lt;tj@kernel.org&gt;
Cc: &lt;stable@vger.kernel.org&gt;	[4.16+]
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>mm: fix vm_fault_t cast in VM_FAULT_GET_HINDEX()</title>
<updated>2019-04-06T02:02:31Z</updated>
<author>
<name>Jann Horn</name>
<email>jannh@google.com</email>
</author>
<published>2019-04-06T01:39:01Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=fcae96ff96538f66e7acd5d4e0f2e7516ff8cbd0'/>
<id>urn:sha1:fcae96ff96538f66e7acd5d4e0f2e7516ff8cbd0</id>
<content type='text'>
Symmetrically to VM_FAULT_SET_HINDEX(), we need a force-cast in
VM_FAULT_GET_HINDEX() to tell sparse that this is intentional.

Sparse complains about the current code when building a kernel with
CONFIG_MEMORY_FAILURE:

  arch/x86/mm/fault.c:1058:53: warning: restricted vm_fault_t degrades to integer

Link: http://lkml.kernel.org/r/20190327204117.35215-1-jannh@google.com
Fixes: 3d3539018d2c ("mm: create the new vm_fault_t type")
Signed-off-by: Jann Horn &lt;jannh@google.com&gt;
Reviewed-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Cc: Souptick Joarder &lt;jrdr.linux@gmail.com&gt;
Cc: Matthew Wilcox &lt;willy@infradead.org&gt;
Cc: Vlastimil Babka &lt;vbabka@suse.cz&gt;
Cc: "Kirill A. Shutemov" &lt;kirill.shutemov@linux.intel.com&gt;
Cc: Rik van Riel &lt;riel@surriel.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>include/linux/bitrev.h: fix constant bitrev</title>
<updated>2019-04-06T02:02:30Z</updated>
<author>
<name>Arnd Bergmann</name>
<email>arnd@arndb.de</email>
</author>
<published>2019-04-06T01:38:53Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=6147e136ff5071609b54f18982dea87706288e21'/>
<id>urn:sha1:6147e136ff5071609b54f18982dea87706288e21</id>
<content type='text'>
clang points out with hundreds of warnings that the bitrev macros have a
problem with constant input:

  drivers/hwmon/sht15.c:187:11: error: variable '__x' is uninitialized when used within its own initialization
        [-Werror,-Wuninitialized]
          u8 crc = bitrev8(data-&gt;val_status &amp; 0x0F);
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  include/linux/bitrev.h:102:21: note: expanded from macro 'bitrev8'
          __constant_bitrev8(__x) :                       \
          ~~~~~~~~~~~~~~~~~~~^~~~
  include/linux/bitrev.h:67:11: note: expanded from macro '__constant_bitrev8'
          u8 __x = x;                     \
             ~~~   ^

Both the bitrev and the __constant_bitrev macros use an internal
variable named __x, which goes horribly wrong when passing one to the
other.

The obvious fix is to rename one of the variables, so this adds an extra
'_'.

It seems we got away with this because

 - there are only a few drivers using bitrev macros

 - usually there are no constant arguments to those

 - when they are constant, they tend to be either 0 or (unsigned)-1
   (drivers/isdn/i4l/isdnhdlc.o, drivers/iio/amplifiers/ad8366.c) and
   give the correct result by pure chance.

In fact, the only driver that I could find that gets different results
with this is drivers/net/wan/slic_ds26522.c, which in turn is a driver
for fairly rare hardware (adding the maintainer to Cc for testing).

Link: http://lkml.kernel.org/r/20190322140503.123580-1-arnd@arndb.de
Fixes: 556d2f055bf6 ("ARM: 8187/1: add CONFIG_HAVE_ARCH_BITREVERSE to support rbit instruction")
Signed-off-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Reviewed-by: Nick Desaulniers &lt;ndesaulniers@google.com&gt;
Cc: Zhao Qiang &lt;qiang.zhao@nxp.com&gt;
Cc: Yalin Wang &lt;yalin.wang@sonymobile.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>lib/string.c: implement a basic bcmp</title>
<updated>2019-04-06T02:02:30Z</updated>
<author>
<name>Nick Desaulniers</name>
<email>ndesaulniers@google.com</email>
</author>
<published>2019-04-06T01:38:45Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=5f074f3e192f10c9fade898b9b3b8812e3d83342'/>
<id>urn:sha1:5f074f3e192f10c9fade898b9b3b8812e3d83342</id>
<content type='text'>
A recent optimization in Clang (r355672) lowers comparisons of the
return value of memcmp against zero to comparisons of the return value
of bcmp against zero.  This helps some platforms that implement bcmp
more efficiently than memcmp.  glibc simply aliases bcmp to memcmp, but
an optimized implementation is in the works.

This results in linkage failures for all targets with Clang due to the
undefined symbol.  For now, just implement bcmp as a tailcail to memcmp
to unbreak the build.  This routine can be further optimized in the
future.

Other ideas discussed:

 * A weak alias was discussed, but breaks for architectures that define
   their own implementations of memcmp since aliases to declarations are
   not permitted (only definitions). Arch-specific memcmp
   implementations typically declare memcmp in C headers, but implement
   them in assembly.

 * -ffreestanding also is used sporadically throughout the kernel.

 * -fno-builtin-bcmp doesn't work when doing LTO.

Link: https://bugs.llvm.org/show_bug.cgi?id=41035
Link: https://code.woboq.org/userspace/glibc/string/memcmp.c.html#bcmp
Link: https://github.com/llvm/llvm-project/commit/8e16d73346f8091461319a7dfc4ddd18eedcff13
Link: https://github.com/ClangBuiltLinux/linux/issues/416
Link: http://lkml.kernel.org/r/20190313211335.165605-1-ndesaulniers@google.com
Signed-off-by: Nick Desaulniers &lt;ndesaulniers@google.com&gt;
Reported-by: Nathan Chancellor &lt;natechancellor@gmail.com&gt;
Reported-by: Adhemerval Zanella &lt;adhemerval.zanella@linaro.org&gt;
Suggested-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Suggested-by: James Y Knight &lt;jyknight@google.com&gt;
Suggested-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Suggested-by: Nathan Chancellor &lt;natechancellor@gmail.com&gt;
Suggested-by: Rasmus Villemoes &lt;linux@rasmusvillemoes.dk&gt;
Acked-by: Steven Rostedt (VMware) &lt;rostedt@goodmis.org&gt;
Reviewed-by: Nathan Chancellor &lt;natechancellor@gmail.com&gt;
Tested-by: Nathan Chancellor &lt;natechancellor@gmail.com&gt;
Reviewed-by: Masahiro Yamada &lt;yamada.masahiro@socionext.com&gt;
Reviewed-by: Andy Shevchenko &lt;andriy.shevchenko@linux.intel.com&gt;
Cc: David Laight &lt;David.Laight@ACULAB.COM&gt;
Cc: Rasmus Villemoes &lt;linux@rasmusvillemoes.dk&gt;
Cc: Namhyung Kim &lt;namhyung@kernel.org&gt;
Cc: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Cc: Alexander Shishkin &lt;alexander.shishkin@linux.intel.com&gt;
Cc: Dan Williams &lt;dan.j.williams@intel.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
</entry>
<entry>
<title>Merge tag 'trace-5.1-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace</title>
<updated>2019-04-05T23:15:57Z</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2019-04-05T23:15:57Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=970b766cfd3f3cb7275bf51144b1678c547882fc'/>
<id>urn:sha1:970b766cfd3f3cb7275bf51144b1678c547882fc</id>
<content type='text'>
Pull syscall-get-arguments cleanup and fixes from Steven Rostedt:
 "Andy Lutomirski approached me to tell me that the
  syscall_get_arguments() implementation in x86 was horrible and gcc
  certainly gets it wrong.

  He said that since the tracepoints only pass in 0 and 6 for i and n
  repectively, it should be optimized for that case. Inspecting the
  kernel, I discovered that all users pass in 0 for i and only one file
  passing in something other than 6 for the number of arguments. That
  code happens to be my own code used for the special syscall tracing.

  That can easily be converted to just using 0 and 6 as well, and only
  copying what is needed. Which is probably the faster path anyway for
  that case.

  Along the way, a couple of real fixes came from this as the
  syscall_get_arguments() function was incorrect for csky and riscv.

  x86 has been optimized to for the new interface that removes the
  variable number of arguments, but the other architectures could still
  use some loving and take more advantage of the simpler interface"

* tag 'trace-5.1-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  syscalls: Remove start and number from syscall_set_arguments() args
  syscalls: Remove start and number from syscall_get_arguments() args
  csky: Fix syscall_get_arguments() and syscall_set_arguments()
  riscv: Fix syscall_get_arguments() and syscall_set_arguments()
  tracing/syscalls: Pass in hardcoded 6 into syscall_get_arguments()
  ptrace: Remove maxargs from task_current_syscall()
</content>
</entry>
<entry>
<title>syscalls: Remove start and number from syscall_set_arguments() args</title>
<updated>2019-04-05T13:27:23Z</updated>
<author>
<name>Steven Rostedt (VMware)</name>
<email>rostedt@goodmis.org</email>
</author>
<published>2019-03-28T00:07:31Z</published>
<link rel='alternate' type='text/html' href='https://git.kobert.dev/pm24.git/commit/?id=32d92586629a8b3637a3c9361709818e25f327ad'/>
<id>urn:sha1:32d92586629a8b3637a3c9361709818e25f327ad</id>
<content type='text'>
After removing the start and count arguments of syscall_get_arguments() it
seems reasonable to remove them from syscall_set_arguments(). Note, as of
today, there are no users of syscall_set_arguments(). But we are told that
there will be soon. But for now, at least make it consistent with
syscall_get_arguments().

Link: http://lkml.kernel.org/r/20190327222014.GA32540@altlinux.org

Cc: Oleg Nesterov &lt;oleg@redhat.com&gt;
Cc: Kees Cook &lt;keescook@chromium.org&gt;
Cc: Andy Lutomirski &lt;luto@amacapital.net&gt;
Cc: Dominik Brodowski &lt;linux@dominikbrodowski.net&gt;
Cc: Dave Martin &lt;dave.martin@arm.com&gt;
Cc: "Dmitry V. Levin" &lt;ldv@altlinux.org&gt;
Cc: x86@kernel.org
Cc: linux-snps-arc@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-c6x-dev@linux-c6x.org
Cc: uclinux-h8-devel@lists.sourceforge.jp
Cc: linux-hexagon@vger.kernel.org
Cc: linux-ia64@vger.kernel.org
Cc: linux-mips@vger.kernel.org
Cc: nios2-dev@lists.rocketboards.org
Cc: openrisc@lists.librecores.org
Cc: linux-parisc@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-s390@vger.kernel.org
Cc: linux-sh@vger.kernel.org
Cc: sparclinux@vger.kernel.org
Cc: linux-um@lists.infradead.org
Cc: linux-xtensa@linux-xtensa.org
Cc: linux-arch@vger.kernel.org
Acked-by: Max Filippov &lt;jcmvbkbc@gmail.com&gt; # For xtensa changes
Acked-by: Will Deacon &lt;will.deacon@arm.com&gt; # For the arm64 bits
Reviewed-by: Thomas Gleixner &lt;tglx@linutronix.de&gt; # for x86
Reviewed-by: Dmitry V. Levin &lt;ldv@altlinux.org&gt;
Signed-off-by: Steven Rostedt (VMware) &lt;rostedt@goodmis.org&gt;
</content>
</entry>
</feed>
