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There is a problem with the current ordering of hibernate code which
leads to deadlocks in some filesystems' memory shrinkers. Namely,
some filesystems use freezable kernel threads that are inactive when
the hibernate memory preallocation is carried out. Those same
filesystems use memory shrinkers that may be triggered by the
hibernate memory preallocation. If those memory shrinkers wait for
the frozen kernel threads, the hibernate process deadlocks (this
happens with XFS, for one example).
Apparently, it is not technically viable to redesign the filesystems
in question to avoid the situation described above, so the only
possible solution of this issue is to defer the freezing of kernel
threads until the hibernate memory preallocation is done, which is
implemented by this change.
Unfortunately, this requires the memory preallocation to be done
before the "prepare" stage of device freeze, so after this change the
only way drivers can allocate additional memory for their freeze
routines in a clean way is to use PM notifiers.
Reported-by: Christoph <cr2005@u-club.de>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
This patch (as1485) documents a change to the kernel's default wakeup
policy. Devices that forward wakeup requests between buses should be
enabled for wakeup by default.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Record S3 failure time about each reason and the latest two failed
devices' names in S3 progress.
We can check it through 'suspend_stats' entry in debugfs.
The motivation of the patch:
We are enabling power features on Medfield. Comparing with PC/notebook,
a mobile enters/exits suspend-2-ram (we call it s3 on Medfield) far
more frequently. If it can't enter suspend-2-ram in time, the power
might be used up soon.
We often find sometimes, a device suspend fails. Then, system retries
s3 over and over again. As display is off, testers and developers
don't know what happens.
Some testers and developers complain they don't know if system
tries suspend-2-ram, and what device fails to suspend. They need
such info for a quick check. The patch adds suspend_stats under
debugfs for users to check suspend to RAM statistics quickly.
If not using this patch, we have other methods to get info about
what device fails. One is to turn on CONFIG_PM_DEBUG, but users
would get too much info and testers need recompile the system.
In addition, dynamic debug is another good tool to dump debug info.
But it still doesn't match our utilization scenario closely.
1) user need write a user space parser to process the syslog output;
2) Our testing scenario is we leave the mobile for at least hours.
Then, check its status. No serial console available during the
testing. One is because console would be suspended, and the other
is serial console connecting with spi or HSU devices would consume
power. These devices are powered off at suspend-2-ram.
Signed-off-by: ShuoX Liu <shuox.liu@intel.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
The following patch for megaraid_sas updates the
ChangeLog.megaraid_sas file and updates the driver version.
Signed-off-by: Adam Radford <aradford@gmail.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
Add support for the msi-address-64 property of a PCI node. This property
specifies the PCI address of MSIIR (message signaled interrupt index
register).
In commit 3da34aae ("powerpc/fsl: Support unique MSI addresses per PCIe Root
Complex"), the msi_addr_hi/msi_addr_lo fields of struct fsl_msi were redefined
from an actual address to just an offset, but the fields were not renamed
accordingly. These fields are replace with a single field, msiir_offset,
to reflect the new meaning.
Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
This creates a subsystem for handling of pin control devices.
These are devices that control different aspects of package
pins.
Currently it handles pinmuxing, i.e. assigning electronic
functions to groups of pins on primarily PGA and BGA type of
chip packages which are common in embedded systems.
The plan is to also handle other I/O pin control aspects
such as biasing, driving, input properties such as
schmitt-triggering, load capacitance etc within this
subsystem, to remove a lot of ARM arch code as well as
feature-creepy GPIO drivers which are implementing the same
thing over and over again.
This is being done to depopulate the arch/arm/* directory
of such custom drivers and try to abstract the infrastructure
they all need. See the Documentation/pinctrl.txt file that is
part of this patch for more details.
ChangeLog v1->v2:
- Various minor fixes from Joe's and Stephens review comments
- Added a pinmux_config() that can invoke custom configuration
with arbitrary data passed in or out to/from the pinmux driver
ChangeLog v2->v3:
- Renamed subsystem folder to "pinctrl" since we will likely
want to keep other pin control such as biasing in this
subsystem too, so let us keep to something generic even though
we're mainly doing pinmux now.
- As a consequence, register pins as an abstract entity separate
from the pinmux. The muxing functions will claim pins out of the
pin pool and make sure they do not collide. Pins can now be
named by the pinctrl core.
- Converted the pin lookup from a static array into a radix tree,
I agreed with Grant Likely to try to avoid any static allocation
(which is crap for device tree stuff) so I just rewrote this
to be dynamic, just like irq number descriptors. The
platform-wide definition of number of pins goes away - this is
now just the sum total of the pins registered to the subsystem.
- Make sure mappings with only a function name and no device
works properly.
ChangeLog v3->v4:
- Define a number space per controller instead of globally,
Stephen and Grant requested the same thing so now maps need to
define target controller, and the radix tree of pin descriptors
is a property on each pin controller device.
- Add a compulsory pinctrl device entry to the pinctrl mapping
table. This must match the pinctrl device, like "pinctrl.0"
- Split the file core.c in two: core.c and pinmux.c where the
latter carry all pinmux stuff, the core is for generic pin
control, and use local headers to access functionality between
files. It is now possible to implement a "blank" pin controller
without pinmux capabilities. This split will make new additions
like pindrive.c, pinbias.c etc possible for combined drivers
and chunks of functionality which is a GoodThing(TM).
- Rewrite the interaction with the GPIO subsystem - the pin
controller descriptor now handles this by defining an offset
into the GPIO numberspace for its handled pin range. This is
used to look up the apropriate pin controller for a GPIO pin.
Then that specific GPIO range is matched 1-1 for the target
controller instance.
- Fixed a number of review comments from Joe Perches.
- Broke out a header file pinctrl.h for the core pin handling
stuff that will be reused by other stuff than pinmux.
- Fixed some erroneous EXPORT() stuff.
- Remove mispatched U300 Kconfig and Makefile entries
- Fixed a number of review comments from Stephen Warren, not all
of them - still WIP. But I think the new mapping that will
specify which function goes to which pin mux controller address
50% of your concerns (else beat me up).
ChangeLog v4->v5:
- Defined a "position" for each function, so the pin controller now
tracks a function in a certain position, and the pinmux maps define
what position you want the function in. (Feedback from Stephen
Warren and Sascha Hauer).
- Since we now need to request a combined function+position from
the machine mapping table that connect mux settings to drivers,
it was extended with a position field and a name field. The
name field is now used if you e.g. need to switch between two
mux map settings at runtime.
- Switched from a class device to using struct bus_type for this
subsystem. Verified sysfs functionality: seems to work fine.
(Feedback from Arnd Bergmann and Greg Kroah-Hartman)
- Define a per pincontroller list of GPIO ranges from the GPIO
pin space that can be handled by the pin controller. These can
be added one by one at runtime. (Feedback from Barry Song)
- Expanded documentation of regulator_[get|enable|disable|put]
semantics.
- Fixed a number of review comments from Barry Song. (Thanks!)
ChangeLog v5->v6:
- Create an abstract pin group concept that can sort pins into
named and enumerated groups no matter what the use of these
groups may be, one possible usecase is a group of pins being
muxed in or so. The intention is however to also use these
groups for other pin control activities.
- Make it compulsory for pinmux functions to associate with
at least one group, so the abstract pin group concept is used
to define the groups of pins affected by a pinmux function.
The pinmux driver interface has been altered so as to enforce
a function to list applicable groups per function.
- Provide an optional .group entry in the pinmux machine map
so the map can select beteween different available groups
to be used with a certain function.
- Consequent changes all over the place so that e.g. debugfs
present reasonable information about the world.
- Drop the per-pin mux (*config) function in the pinmux_ops
struct - I was afraid that this would start to be used for
things totally unrelated to muxing, we can introduce that to
the generic struct pinctrl_ops if needed. I want to keep
muxing orthogonal to other pin control subjects and not mix
these things up.
ChangeLog v6->v7:
- Make it possible to have several map entries matching the
same device, pin controller and function, but using
a different group, and alter the semantics so that
pinmux_get() will pick all matching map entries, and
store the associated groups in a list. The list will
then be iterated over at pinmux_enable()/pinmux_disable()
and corresponding driver functions called for each
defined group. Notice that you're only allowed to map
multiple *groups* to the same
{ device, pin controller, function } triplet, attempts
to map the same device to multiple pin controllers will
for example fail. This is hopefully the crucial feature
requested by Stephen Warren.
- Add a pinmux hogging field to the pinmux mapping entries,
and enable the pinmux core to hog pinmux map entries.
This currently only works for pinmuxes without assigned
devices as it looks now, but with device trees we can
look up the corresponding struct device * entries when
we register the pinmux driver, and have it hog each
pinmux map in turn, for a simple approach to
non-dynamic pin muxing. This addresses an issue from
Grant Likely that the machine should take care of as
much of the pinmux setup as possible, not the devices.
By supplying a list of hogs, it can now instruct the
core to take care of any static mappings.
- Switch pinmux group retrieveal function to grab an
array of strings representing the groups rather than an
array of unsigned and rewrite accordingly.
- Alter debugfs to show the grouplist handled by each
pinmux. Also add a list of hogs.
- Dynamically allocate a struct pinmux at pinmux_get() and
free it at pinmux_put(), then add these to the global
list of pinmuxes active as we go along.
- Go over the list of pinmux maps at pinmux_get() time
and repeatedly apply matches.
- Retrieve applicable groups per function from the driver
as a string array rather than a unsigned array, then
lookup the enumerators.
- Make the device to pinmux map a singleton - only allow the
mapping table to be registered once and even tag the
registration function with __init so it surely won't be
abused.
- Create a separate debugfs file to view the pinmux map at
runtime.
- Introduce a spin lock to the pin descriptor struct, lock it
when modifying pin status entries. Reported by Stijn Devriendt.
- Fix up the documentation after review from Stephen Warren.
- Let the GPIO ranges give names as const char * instead of some
fixed-length string.
- add a function to unregister GPIO ranges to mirror the
registration function.
- Privatized the struct pinctrl_device and removed it from the
<linux/pinctrl/pinctrl.h> API, the drivers do not need to know
the members of this struct. It is now in the local header
"core.h".
- Rename the concept of "anonymous" mux maps to "system" muxes
and add convenience macros and documentation.
ChangeLog v7->v8:
- Delete the leftover pinmux_config() function from the
<linux/pinctrl/pinmux.h> header.
- Fix a race condition found by Stijn Devriendt in pin_request()
ChangeLog v8->v9:
- Drop the bus_type and the sysfs attributes and all, we're not on
the clear about how this should be used for e.g. userspace
interfaces so let us save this for the future.
- Use the right name in MAINTAINERS, PIN CONTROL rather than
PINMUX
- Don't kfree() the device state holder, let the .remove() callback
handle this.
- Fix up numerous kerneldoc headers to have one line for the function
description and more verbose documentation below the parameters
ChangeLog v9->v10:
- pinctrl: EXPORT_SYMBOL needs export.h, folded in a patch
from Steven Rothwell
- fix pinctrl_register error handling, folded in a patch from
Axel Lin
- Various fixes to documentation text so that it's consistent.
- Removed pointless comment from drivers/Kconfig
- Removed dependency on SYSFS since we removed the bus in
v9.
- Renamed hopelessly abbreviated pctldev_* functions to the
more verbose pinctrl_dev_*
- Drop mutex properly when looking up GPIO ranges
- Return NULL instead of ERR_PTR() errors on registration of
pin controllers, using cast pointers is fragile. We can
live without the detailed error codes for sure.
Cc: Stijn Devriendt <highguy@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Russell King <linux@arm.linux.org.uk>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Barry Song <21cnbao@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Adding new device tree binding file for the DCSR node. Modifying device
tree dtsi files to add DCSR node for P2041, P3041, P4080, & P5020.
Signed-off-by: Stephen George <stephen.george@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Standarize and document the FPGA nodes used on Freescale QorIQ reference
boards. There are different kinds of FPGAs used on the boards, but
only two are currently standard: "pixis", "ngpixis", and "qixis". Although
there are minor differences among the boards that have one kind of FPGA, most
of the functionality is the same, so it makes sense to create common
compatibility strings.
We also need to update the P1022DS platform file, because the compatible
string for its PIXIS node has changed. This means that older kernels are
not compatible with newer device trees. This is not a real problem, however,
since that particular function doesn't work anyway. When the DIU is active,
the PIXIS is in "indirect mode", and so cannot be accessed as a memory-mapped
device.
Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Add a pinmux node to tegra20.dtsi in order to instantiate the future
pinmux device.
v2: Specify reg property precisely; don't just point at the whole APB_MISC
register range.
Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>
Add documentation about NOACK tx flag usage.
Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This UML breakage:
linux-2.6.30.1[3800] vsyscall fault (exploit attempt?) ip:ffffffffff600000 cs:33 sp:7fbfb9c498 ax:ffffffffff600000 si:0 di:606790
linux-2.6.30.1[3856] vsyscall fault (exploit attempt?) ip:ffffffffff600000 cs:33 sp:7fbfb13168 ax:ffffffffff600000 si:0 di:606790
Is caused by commit 3ae36655 ("x86-64: Rework vsyscall emulation and add
vsyscall= parameter") - the vsyscall emulation code is not fully cooked
yet as UML relies on some rather fragile SIGSEGV semantics.
Linus suggested in https://lkml.org/lkml/2011/8/9/376 to default
to vsyscall=native for now, this patch implements that.
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Andrew Lutomirski <luto@mit.edu>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Link: http://lkml.kernel.org/r/20111005214047.GE14406@localhost.pp.htv.fi
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Support for device power domains has been introduced in
commit 9659cc0678b954f187290c6e8b247a673c5d37e1 (PM: Make
system-wide PM and runtime PM treat subsystems consistently),
also power domain callbacks will take precedence over subsystem ones
from commit 4d27e9dcff00a6425d779b065ec8892e4f391661(PM: Make
power domain callbacks take precedence over subsystem ones).
So update part of "Device Runtime PM Callbacks" in
Documentation/power/runtime_pm.txt.
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
For a long time now orlov is the default block allocator in the
ext4. It performs better than the old one and no one seems to claim
otherwise so we can safely drop it and make oldalloc and orlov mount
option deprecated.
This is a part of the effort to reduce number of ext4 options hence the
test matrix.
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Acl and user_xattr mount options are no longer needed since those
features are enabled by default if configured in (seee commit
ea6633369458992241599c9d9ebadffaeddec164). We can not easily deprecate
mount options itself (since it is probably too early), but we can
remove it from documentation first.
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
* pm-runtime:
PM / Tracing: build rpm-traces.c only if CONFIG_PM_RUNTIME is set
PM / Runtime: Replace dev_dbg() with trace_rpm_*()
PM / Runtime: Introduce trace points for tracing rpm_* functions
PM / Runtime: Don't run callbacks under lock for power.irq_safe set
USB: Add wakeup info to debugging messages
PM / Runtime: pm_runtime_idle() can be called in atomic context
PM / Runtime: Add macro to test for runtime PM events
PM / Runtime: Add might_sleep() to runtime PM functions
The mechanism used for connecting regulators together when one regulator
supplies another wasn't clear as the names being used weren't really tied
together well.
Reported-by: Philip Rakity <prakity@marvell.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
The documentation for the machine driver was rather badly bitrotted,
using pointers to struct device rather than dev_name() to hook up the
consumers. Update to use dev_name().
Reported-by: Philip Rakity <prakity@marvell.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
The second hunk fixes rps_sock_flow_table but has to re-wrap the paragraph.
Signed-off-by: Benjamin Poirier <benjamin.poirier@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cintiq 21ux2 has two sets of four LEDs on right and left side of
the tablet, respectively.
Reviewed-by: Eduard Hasenleithner <eduard@hasenleithner.at>
Tested-by: Eduard Hasenleithner <eduard@hasenleithner.at>
Signed-off-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
The LED also indicates the status of the tablet. Don't turn it off.
Reviewed-by: Eduard Hasenleithner <eduard@hasenleithner.at>
Tested-by: Eduard Hasenleithner <eduard@hasenleithner.at>
Signed-off-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
The LED luminance level is normally lower when no button is pressed.
Reviewed-by: Eduard Hasenleithner <eduard@hasenleithner.at>
Tested-by: Eduard Hasenleithner <eduard@hasenleithner.at>
Signed-off-by: Ping Cheng <pingc@wacom.com>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>
Add nodes for devices used by PM code (mpu, dsp, iva).
Add a cpus node as well as recommended in the DT spec.
Remove mpu, dsp, iva devices init if is populated.
Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Kevin Hilman <khilman@ti.com>
Add device-tree support for the l3-noc driver.
Use platform_driver_register to defer the probing at device init
time.
Add documentation for the l3-noc bindings.
Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Update the documentation for the recently updated pm_qos API, kernel
and user space. Add documentation for the per-device PM QoS
(dev_pm_qos) framework API.
Signed-off-by: Jean Pihet <j-pihet@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
The following patch adds support for streams
to dwc3 driver.
While at that, also fix one small issue on
endpoint disable where we should clear all
flags not only ENABLED.
Reviewied-by: Paul Zimmerman <paulz@synopsys.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Add a notifier called during device_add phase. If an of_node is present,
retrieve the hwmod entry in order to populate properly the omap_device
structure.
For the moment the resource from the device-tree are overloaded.
DT does not support named resource yet, and thus, most driver will not
work without that information.
Add a documentation to capture the specifics OMAP bindings needed for
device-tree support.
Signed-off-by: Benoit Cousson <b-cousson@ti.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Kevin Hilman <khilman@ti.com>
* Channel Mode
This is an enum control to change the surround-channel setup,
appears only when the surround channels are available.
It gives the number of channels to be used, "2ch", "4ch" abd "6ch".
According to the configuration, this also controls the
jack-retasking of multi-I/O jacks.
* Independent HP
When this enum control is enabled, the headphone output is routed
from an individual stream (the third PCM such as hw:0,2) instead of
the primary stream.
Signed-off-by: Raymond Yau <superquad.vortex2@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Rename the iwlagn module as iwlwifi in preparation for future
changes. Add an alias to iwlagn for backward compatibility.
Signed-off-by: Don Fry <donald.h.fry@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Four cpufreq-like governors are provided as examples.
powersave: use the lowest frequency possible. The user (device) should
set the polling_ms as 0 because polling is useless for this governor.
performance: use the highest freqeuncy possible. The user (device)
should set the polling_ms as 0 because polling is useless for this
governor.
userspace: use the user specified frequency stored at
devfreq.user_set_freq. With sysfs support in the following patch, a user
may set the value with the sysfs interface.
simple_ondemand: simplified version of cpufreq's ondemand governor.
When a user updates OPP entries (enable/disable/add), OPP framework
automatically notifies devfreq to update operating frequency
accordingly. Thus, devfreq users (device drivers) do not need to update
devfreq manually with OPP entry updates or set polling_ms for powersave
, performance, userspace, or any other "static" governors.
Note that these are given only as basic examples for governors and any
devices with devfreq may implement their own governors with the drivers
and use them.
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mike Turquette <mturquette@ti.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Device specific sysfs interface /sys/devices/.../power/devfreq_*
- governor R: name of governor
- cur_freq R: current frequency
- polling_interval R: polling interval in ms given with devfreq profile
W: update polling interval.
- central_polling R: 1 if polling is managed by devfreq framework
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mike Turquette <mturquette@ti.com>
Acked-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
--
Documentation/ABI/testing/sysfs-class-devfreq | 44 ++++++++++++++++
drivers/devfreq/devfreq.c | 69 ++++++++++++++++++++++++++
2 files changed, 113 insertions(+)
create mode 100644 Documentation/ABI/testing/sysfs-class-devfreq
With the addition of uAPSD and driver buffering
the powersave handling has gotten quite complex.
Add a section to the documentation to explain it
for anyone wanting to implement it.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
There has been quite a bit of confusion about what RCU-lockdep splats
mean, so this commit adds some documentation describing how to
interpret them.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Add documentation for rcu_dereference_bh_check(),
rcu_dereference_sched_check(), srcu_dereference_check(), and
rcu_dereference_index_check().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Since ca5ecddf (rcu: define __rcu address space modifier for sparse)
rcu_dereference_check() use rcu_read_lock_held() as a part of condition
automatically. Therefore, callers of rcu_dereference_check() no longer
need to pass rcu_read_lock_held() to rcu_dereference_check().
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
There is often a delay between the time that a CPU passes through a
quiescent state and the time that this quiescent state is reported to the
RCU core. It is quite possible that the grace period ended before the
quiescent state could be reported, for example, some other CPU might have
deduced that this CPU passed through dyntick-idle mode. It is critically
important that quiescent state be counted only against the grace period
that was in effect at the time that the quiescent state was detected.
Previously, this was handled by recording the number of the last grace
period to complete when passing through a quiescent state. The RCU
core then checks this number against the current value, and rejects
the quiescent state if there is a mismatch. However, one additional
possibility must be accounted for, namely that the quiescent state was
recorded after the prior grace period completed but before the current
grace period started. In this case, the RCU core must reject the
quiescent state, but the recorded number will match. This is handled
when the CPU becomes aware of a new grace period -- at that point,
it invalidates any prior quiescent state.
This works, but is a bit indirect. The new approach records the current
grace period, and the RCU core checks to see (1) that this is still the
current grace period and (2) that this grace period has not yet ended.
This approach simplifies reasoning about correctness, and this commit
changes over to this new approach.
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
