If ohci-platform is runtime suspended, we can currently get an "imprecise
external abort" on reboot with ohci-platform loaded when PM runtime
is implemented for the SoC.

Let's fix this by adding PM runtime support to usb_hcd_platform_shutdown.
Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

device_create_file() could fail and return an error code. The fix
captures the error and returns the error code upstream in case it
indeed failed.
Signed-off-by: Kangjie Lu <kjlu@umn.edu>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

By introducing mailbox_state_string(), allow to make debug
log more readable
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This patch implements a few initial tracepoints for the
mtu3 driver. More traces can be added as necessary in order
to ease the task of debugging.
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Due to the separated debugfs files are added, move vbus and mode
debugfs interfaces related with dual-role switch from mtu3_dr.c
into mtu3_debugfs.c
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

This adds more debugfs consumers. The debugfs entries read some
important registers, fifo status, QMU ring, endpoint status, and
IPPC probe interface to get internal status.
With these entries, users can check the registers, endpoint and
GPD used during run time.
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

In order to support U3gen2 ISOC transfer upto 96DPs, extend
the data buffer length.
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

To support USB3 Gen2 ISOC, the data buffer length need be extended,
it's hard to make the current qmu_gpd struct compatible, so here
rebuild qmu_gpd struct and make easy to support new QMU format
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

To support USB3 Gen2 ISOC, the registers of TXCSR1 and RXCSR1
are adjusted to support greater maxpkt and mult value, this
patch fix this issue
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Remove local variable @vbus and use @dev instead of @pdev->dev
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The local variable @req is unnecessary in qmu_tx_zlp_error_handler,
so remove it.
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Print useful information not only dual-role mode but also
device mode and host mode.
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Check the return value of devm_extcon_register_notifier() and
add error handling.
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Add __printf attribute to fusb302_log function, so that we get
compiler warnings when specifying wrong vararg parameters.
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Remove the code which avoids doing i2c-transfers while our parent
i2c-adapter may be suspended by busy-waiting for our resume handler
to be called.

Instead move the interrupt handling from a threaded interrupt handler
to a work-queue and install a non-threaded interrupt handler which
normally queues the new interrupt handling work directly.

When our suspend handler gets called we set a flag which makes the new
non-threaded interrupt handler skip queueing the work before our parent
i2c-adapter is ready, instead the new non-threaded handler will record an
interrupt has happened during suspend and then our resume handler will
queue the work (at which point our parent will be ready).

Note normally i2c drivers solve the problem of not being able to access
the i2c bus until the i2c-controller is resumed by simply disabling their
irq from the suspend handler and re-enabling it on resume.

That is not possible with the fusb302 since the irq is a wakeup source
(it must be a wakeup source so that we can do PD negotiation when a
charger gets plugged in while suspended).

Besides avoiding the ugly busy-wait, this also fixes the following errors
which were logged by the busy-wait code when woken from suspend by plugging
in a Type-C device:

fusb302: i2c: pm suspend, retry 1 / 10
fusb302: i2c: pm suspend, retry 2 / 10
etc.

This commit also changes the devm_request_irq to a regular request_irq
+ free_irq, so that the work can be properly stopped. While at it also
properly disable the wake setting on the irq and also properly stop the
delayed work for bcl handling.
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Fix a copy and paste error in an error message and a spelling error
in a comment.
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The FUSB302 will stop toggling with a FUSB_REG_STATUS1A_TOGSS_SRC? status,
as soon as it sees either Ra or Rd on a CC pin.

Before this commit fusb302_handle_togdone_src would assume that the toggle-
engine always stopped at the CC pin indicating the polarity, IOW it assumed
that it stopped at the pin connected to Rd. It did check the CC-status of
that pin, but it did not expect to get a CC-status of Ra and therefore
treated this as CC-open. This lead to the following 2 problems:

1) If a powered cable/adapter gets plugged in with Ra on CC1 and Rd on CC2
then 4 of 5 times when plugged in toggling will stop with a togdone_result
of FUSB_REG_STATUS1A_TOGSS_SRC1.  3/5th of the time the toggle-engine is
testing for being connected as a sink and after that it tests 1/5th of the
time for connected as a src through CC1 before finally testing the last
1/5th of the time for being a src connected through CC2.

This was a problem because we would only check the CC pin status for the
pin on which the toggling stopped which in this polarity 4 out of 5
times would be the Ra pin. The code before this commit would treat Ra as
CC-open and then restart toggling. Once toggling is restarted we are
guaranteed to end with FUSB_REG_STATUS1A_TOGSS_SRC1 as CC1 is tested first,
leading to a CC-status of Ra again and an infinite restart toggling loop.
So 4 out of 5 times when plugged in in this polarity a powered adapter
will not work.

2) Even if we happen to have the right polarity or 1/5th of the time in
the polarity with problem 1), we would report the non Rd pin as CC-open
rather then as Ra, resulting in the tcpm.c code not enabling Vconn which
is a problem for some adapters.

This commit fixes this by getting the CC-status of *both* pins and then
determining the polarity based on that, rather then on where the toggling
stopped.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The datasheet says the vconn MUST be off when we start toggling. The
tcpm.c state-machine is responsible to make sure vconn is off, but lets
add a WARN to catch any cases where vconn is not off for some reason.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

After the recent cleanups, tcpm_set_cc is the only caller of
fusb302_set_cc_pull, fold fusb302_set_cc_pull directly into
tcpm_set_cc for a nice cleanup.
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

After commit ea3b4d55 ("usb: typec: fusb302: Resolve fixed power role
contract setup"), tcpm_set_cc always calls fusb302_set_toggling.

Before this refactor tcpm_set_cc does the following:

1) fusb302_set_toggling(TOGGLING_MODE_OFF),
   this sets both FUSB_REG_MASK_BC_LVL and FUSB_REG_MASK_COMP_CHNG.
2) fusb302_set_cc_pull(...).
3) "reset cc status".
4) if pull-up fusb302_set_src_current(...).
5) if pull-up or pull-down enable bc-lvl resp comp-chng irq.
6) fusb302_set_toggling(new-toggling-mode), which again
   sets both FUSB_REG_MASK_BC_LVL and FUSB_REG_MASK_COMP_CHNG disabling
   the just enabled irq. fusb302_set_toggling is skipped when the new
   toggling mode is TOGGLING_MODE_OFF because this is already done in 1,
   note in this case 5) is a no-op.

When we are toggling the bits set by fusb302_set_cc_pull will be ignored
until we turn toggling off, so we can safely move the fusb302_set_cc_pull
call to before setting TOGGLING_MODE_OFF.

Either we are not toggling yet, or the src-current has already been set,
so we can also safely set the src-current earlier, allowing us to do the
fusb302_set_toggling(TOGGLING_MODE_OFF) call at the same time as we
set the other toggling modes. Also setting the src-current is a no-op
when not enabling pull-ups, so we can drop the if.

And since the second fusb302_set_toggling undoes the effects of step 5,
we can skip step 5, the bc-lvl resp comp-chng irq wil be enabled by
fusb302_handle_togdone_snk resp. fusb302_handle_togdone_src when toggling
is done.

Together this allows us to simplify things to:

1) fusb302_set_cc_pull(...)
2) "reset cc status"
3) fusb302_set_src_current(...)
4) fusb302_set_toggling(new-toggling-mode)

This commit does this, leading to a nice cleanup.
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

The 2 callers of fusb302_set_cc_polarity both call fusb302_set_cc_pull
directly before calling fusb302_set_cc_polarity, this is not ideal for
2 reasons:

1) fusb302_set_cc_pull uses the cached polarity when applying the pull-ups,
which maybe changed immediately afterwards, to fix this set_cc_polarity
already does the pull-up setting.

2) Both touch the SWITCHES0 register in a r-w-modify cycle, this leads to
read reg, write reg, read reg, write reg. If we fold the setting of
the pull-downs into fusb302_set_cc_polarity then not only can we avoid
doing the reads / writes twice, at this point we set all bits, so we
can skip the read, turning 4 (slowish) i2c-transfers into 1.

Doing this also avoids the need to cache the pull_up state in
struct fusb302_chip.
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Keep the orientation value when setting the mux to safe mode, this
fixes the orientation getting reset when switching alt-modes.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

If our port-partner supports both DP-only operation (pin-assignment C)
and multi-func operation (pin-assignment D) and we only support
pin-assignment D and the port-partner prefers DP-only mode, then
before this commit we would and up masking out pin-assignment D from
the available pin-assignments and fail to pick a pin-assignment.

Instead only mask out the multi-func pin-assignments if we support
dp-only pin-assignments, so that we correctly fall-back to a multi-func
pin-assignment in this case (by picking pin-assignment D).
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

"vdev" points to vhci_hcd->vdev[] array and vhci_hcd->vdev[] array
is not a pointer array but a structure array and it is already used
in vhci_urb_enqueue() and then passed to vhci_tx_urb() as an argument.
vhci_tx_urb() is not called except vhci_urb_enqueue(). So, "vdev"
can not be null pointer. This null check statement is meaningless.
Signed-off-by: Suwan Kim <suwan.kim027@gmail.com>
Acked-by: Shuah Khan <shuah@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

By moving one field around in 'struct urb' we reduce the size of the
structure by 8 bytes.

Before the patch on x86_64 the overall size of the structure as reported
by pahole was:
	/* size: 192, cachelines: 3, members: 30 */
	/* sum members: 184, holes: 2, sum holes: 8 */
After the patch we now have:
	/* size: 184, cachelines: 3, members: 30 */
	/* last cacheline: 56 bytes */
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull more Kbuild updates from Masahiro Yamada:

 - add more Build-Depends to Debian source package

 - prefix header search paths with $(srctree)/

 - make modpost show verbose section mismatch warnings

 - avoid hard-coded CROSS_COMPILE for h8300

 - fix regression for Debian make-kpkg command

 - add semantic patch to detect missing put_device()

 - fix some warnings of 'make deb-pkg'

 - optimize NOSTDINC_FLAGS evaluation

 - add warnings about redundant generic-y

 - clean up Makefiles and scripts

* tag 'kbuild-v5.1-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
  kconfig: remove stale lxdialog/.gitignore
  kbuild: force all architectures except um to include mandatory-y
  kbuild: warn redundant generic-y
  Revert "modsign: Abort modules_install when signing fails"
  kbuild: Make NOSTDINC_FLAGS a simply expanded variable
  kbuild: deb-pkg: avoid implicit effects
  coccinelle: semantic code search for missing put_device()
  kbuild: pkg: grep include/config/auto.conf instead of $KCONFIG_CONFIG
  kbuild: deb-pkg: introduce is_enabled and if_enabled_echo to builddeb
  kbuild: deb-pkg: add CONFIG_ prefix to kernel config options
  kbuild: add workaround for Debian make-kpkg
  kbuild: source include/config/auto.conf instead of ${KCONFIG_CONFIG}
  unicore32: simplify linker script generation for decompressor
  h8300: use cc-cross-prefix instead of hardcoding h8300-unknown-linux-
  kbuild: move archive command to scripts/Makefile.lib
  modpost: always show verbose warning for section mismatch
  ia64: prefix header search path with $(srctree)/
  libfdt: prefix header search paths with $(srctree)/
  deb-pkg: generate correct build dependencies

Pull x86 asm updates from Thomas Gleixner:
 "Two cleanup patches removing dead conditionals and unused code"

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/asm: Remove unused __constant_c_x_memset() macro and inlines
  x86/asm: Remove dead __GNUC__ conditionals

Pull perf fixes from Thomas Gleixner:
 "Three fixes for the fallout from the TSX errata workaround:

   - Prevent memory corruption caused by a unchecked out of bound array
     index.

   - Two trivial fixes to address compiler warnings"

* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/x86/intel: Make dev_attr_allow_tsx_force_abort static
  perf/x86: Fixup typo in stub functions
  perf/x86/intel: Fix memory corruption

Pull xen fix from Juergen Gross:
 "A fix for a Xen bug introduced by David's series for excluding
  ballooned pages in vmcores"

* tag 'for-linus-5.1b-rc1b-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/balloon: Fix mapping PG_offline pages to user space

Pull 9p updates from Dominique Martinet:
 "Here is a 9p update for 5.1; there honestly hasn't been much.

  Two fixes (leak on invalid mount argument and possible deadlock on
  i_size update on 32bit smp) and a fall-through warning cleanup"

* tag '9p-for-5.1' of git://github.com/martinetd/linux:
  9p/net: fix memory leak in p9_client_create
  9p: use inode->i_lock to protect i_size_write() under 32-bit
  9p: mark expected switch fall-through

Fixes: 400816f6 ("perf/x86/intel: Implement support for TSX Force Abort")
Signed-off-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: "Peter Zijlstra (Intel)" <peterz@infradead.org>
Cc: kbuild-all@01.org
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20190313184243.GA10820@lkp-sb-ep06

When this .gitignore was added, lxdialog was an independent hostprogs-y.

Now that all objects in lxdialog/ are directly linked to mconf, the
lxdialog is no longer generated.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Currently, every arch/*/include/uapi/asm/Kbuild explicitly includes
the common Kbuild.asm file. Factor out the duplicated include directives
to scripts/Makefile.asm-generic so that no architecture would opt out
of the mandatory-y mechanism.

um is not forced to include mandatory-y since it is a very exceptional
case which does not support UAPI.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The generic-y is redundant under the following condition:

 - arch has its own implementation

 - the same header is added to generated-y

 - the same header is added to mandatory-y

If a redundant generic-y is found, the warning like follows is displayed:

  scripts/Makefile.asm-generic:20: redundant generic-y found in arch/arm/include/asm/Kbuild: timex.h

I fixed up arch Kbuild files found by this.
Suggested-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

This reverts commit caf6fe91.

The commit was fine but is no longer needed as of commit 3a2429e1
("kbuild: change if_changed_rule for multi-line recipe").  Let's go
back to using ";" to be consistent.

For some discussion, see:

https://lkml.kernel.org/r/CAK7LNASde0Q9S5GKeQiWhArfER4S4wL1=R_FW8q0++_X3T5=hQ@mail.gmail.comSigned-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

During a simple no-op (nothing changed) build I saw 39 invocations of
the C compiler with the argument "-print-file-name=include".  We don't
need to call the C compiler 39 times for this--one time will suffice.

Let's change NOSTDINC_FLAGS to a simply expanded variable to avoid
this since there doesn't appear to be any reason it should be
recursively expanded.

On my build this shaved ~400 ms off my "no-op" build.

Note that the recursive expansion seems to date back to the (really
old) commit e8f5bdb0 ("[PATCH] Makefile include path ordering").
It's a little unclear to me if the point of that patch was to switch
the variable to be recursively expanded (which it did) or to avoid
directly assigning to NOSTDINC_FLAGS (AKA to switch to +=) because
someone else (out of tree?) was setting it.  I presume later since if
the only goal was to switch to recursive expansion the patch would
have just removed the ":".
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

* The man page for dpkg-source(1) notes:

>      -b, --build directory [format-specific-parameters]
>             Build  a  source  package  (--build since dpkg 1.17.14).
>             <...>
>
>             dpkg-source will build the source package with the first
>             format found in this ordered list: the format  indicated
>             with  the  --format  command  line  option,  the  format
>             indicated in debian/source/format, “1.0”.  The  fallback
>             to “1.0” is deprecated and will be removed at some point
>             in the future, you should always  document  the  desired
>             source   format  in  debian/source/format.  See  section
>             SOURCE PACKAGE FORMATS for an extensive  description  of
>             the various source package formats.

  Thus it would be more foolproof to explicitly use 1.0 (as we always
  did) than to rely on dpkg-source's defaults.

* In a similar vein, debian/rules is not made executable by mkdebian,
  and dpkg-source warns about that but still silently fixes the file.
  Let's be explicit once again.
Signed-off-by: Arseny Maslennikov <ar@cs.msu.ru>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

The of_find_device_by_node() takes a reference to the underlying device
structure, we should release that reference.
The implementation of this semantic code search is:
In a function, for a local variable returned by calling
of_find_device_by_node(),
a, if it is released by a function such as
   put_device()/of_dev_put()/platform_device_put() after the last use,
   it is considered that there is no reference leak;
b, if it is passed back to the caller via
   dev_get_drvdata()/platform_get_drvdata()/get_device(), etc., the
   reference will be released in other functions, and the current function
   also considers that there is no reference leak;
c, for the rest of the situation, the current function should release the
   reference by calling put_device, this code search will report the
   corresponding error message.

By using this semantic code search, we have found some object reference leaks,
such as:
commit 11907e9d ("ASoC: fsl-asoc-card: fix object reference leaks in
fsl_asoc_card_probe")
commit a12085d1 ("mtd: rawnand: atmel: fix possible object reference leak")
commit 11493f26 ("mtd: rawnand: jz4780: fix possible object reference leak")

There are still dozens of reference leaks in the current kernel code.

Further, for the case of b, the object returned to other functions may also
have a reference leak, we will continue to develop other cocci scripts to
further check the reference leak.
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Reviewed-by: Julia Lawall <Julia.Lawall@lip6.fr>
Reviewed-by: Markus Elfring <Markus.Elfring@web.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

Pull pidfd system call from Christian Brauner:
 "This introduces the ability to use file descriptors from /proc/<pid>/
  as stable handles on struct pid. Even if a pid is recycled the handle
  will not change. For a start these fds can be used to send signals to
  the processes they refer to.

  With the ability to use /proc/<pid> fds as stable handles on struct
  pid we can fix a long-standing issue where after a process has exited
  its pid can be reused by another process. If a caller sends a signal
  to a reused pid it will end up signaling the wrong process.

  With this patchset we enable a variety of use cases. One obvious
  example is that we can now safely delegate an important part of
  process management - sending signals - to processes other than the
  parent of a given process by sending file descriptors around via scm
  rights and not fearing that the given process will have been recycled
  in the meantime. It also allows for easy testing whether a given
  process is still alive or not by sending signal 0 to a pidfd which is
  quite handy.

  There has been some interest in this feature e.g. from systems
  management (systemd, glibc) and container managers. I have requested
  and gotten comments from glibc to make sure that this syscall is
  suitable for their needs as well. In the future I expect it to take on
  most other pid-based signal syscalls. But such features are left for
  the future once they are needed.

  This has been sitting in linux-next for quite a while and has not
  caused any issues. It comes with selftests which verify basic
  functionality and also test that a recycled pid cannot be signaled via
  a pidfd.

  Jon has written about a prior version of this patchset. It should
  cover the basic functionality since not a lot has changed since then:

      https://lwn.net/Articles/773459/

  The commit message for the syscall itself is extensively documenting
  the syscall, including it's functionality and extensibility"

* tag 'pidfd-v5.1-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux:
  selftests: add tests for pidfd_send_signal()
  signal: add pidfd_send_signal() syscall