The script "checkpatch.pl" pointed information out like the following.
ERROR: space required before the open parenthesis '('
Thus fix the affected source code place.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
The script "checkpatch.pl" pointed information out like the following.
WARNING: Possible unnecessary 'out of memory' message
Thus remove such statements here.
Link: http://events.linuxfoundation.org/sites/events/files/slides/LCJ16-Refactor_Strings-WSang_0.pdf
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
* A multiplication for the size determination of a memory allocation
indicated that an array data structure should be processed.
Thus use the corresponding function "devm_kcalloc".
This issue was detected by using the Coccinelle software.
* Replace the specification of a data structure by a pointer dereference
to make the corresponding size determination a bit safer according to
the Linux coding style convention.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
We are now booting all mach-omap2 in device tree only mode.
Any code that is only called in legacy boot mode where
of_have_populated_dt() is not set is safe to remove now.
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
[tony@atomide.com: left out probe changes to avoid merge conflict]
Signed-off-by: Tony Lindgren <tony@atomide.com>
We are now booting all mach-omap2 in device tree only mode.
Any code that is only called in legacy boot mode where
of_have_populated_dt() is not set is safe to remove now.
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>
We are now booting all mach-omap2 in device tree only mode.
Any code that is only called in legacy boot mode where
of_have_populated_dt() is not set is safe to remove now.
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>
We are now booting all mach-omap2 in device tree only mode.
Any code that is only called in legacy boot mode where
of_have_populated_dt() is not set is safe to remove now.
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>
We are now booting all mach-omap2 in device tree only mode.
Any code that is only called in legacy boot mode where
of_have_populated_dt() is not set is safe to remove now.
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>
We are now booting all mach-omap2 in device tree only mode.
Any code that is only called in legacy boot mode where
of_have_populated_dt() is not set is safe to remove now.
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Translate hardware port connector type data into link mode supported and
advertised info instead of caching it in driver.
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Read port connector type from the firmware instead of caching it in the
driver metadata.
Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Update struct mlx5_ifc_create(modify)_flow_table_bits according to
the last device specification.
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Using a per field mask field, the TC pedit action supports modifying
partial fields. E.g if using the TC tool, the following example would
make the kernel to only re-write two bytes of the src ip address:
tc filter add dev enp1s0 protocol ip parent ffff: prio 30
flower skip_sw ip_proto udp dst_port 8001
action pedit ex munge ip src set 10.1.0.0 retain 0xffff0000
We add driver support for offload these partial re-writes, by setting
the per FW action offset-in-field and length-from-offset attributes.
The 1st bit set in the mask specifies both the offset and the right
shift to apply on the value such that the 1st bit which needs to be
set will reside in bit 0 of the FW data field.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Use the modify header ID cache for the header re-write part of offloading
TC NIC flows.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Use the modify header ID cache for the header re-write part of offloading
TC eswitch flows.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Packets belonging to flows which are different by matching may still need
to go through the same header re-write. Add a cache for header re-write IDs
keyed by the binary chain of modify header actions.
The caching is supported for both eswitch and NIC use-cases, where the
actual conversion of the code to use caching comes in next patches, one
per use-case.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Instead of going through flow->nic/esw_attr for each usage, assign
an attr pointer per the context (nic or esw) and use that.
This patch doesn't add any functionality.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Remove the limitation that offloaded NIC filters can have only one
action. This allows us for example to provide flow tag as a note
to upper layers / apps that that HW header re-write was applied.
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Reviewed-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
On the CPCAP PMIC we can use the ADCs for monitoring the battery,
and there is also a coulomb counter. So let's add basic support for
the battery driver.
I did not add any capacity prediction as that should probably be
done in the user space. Or at least user space should tell the kernel
some battery statistics and then the kernel driver could display the
capacity based on that.
Cc: devicetree@vger.kernel.org
Cc: Marcel Partap <mpartap@gmx.net>
Cc: Michael Scott <michael.scott@linaro.org>
Cc: Rob Herring <robh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Add binding for cpcap pmic battery.
Cc: devicetree@vger.kernel.org
Cc: Marcel Partap <mpartap@gmx.net>
Cc: Michael Scott <michael.scott@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
On Broadcom MIPS STB platforms, BMIPS_GENERIC is the Kconfig symbol that
is used, make this reboot driver default to that value to make sure we
can reboot a system properly.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Since commit 37eb56dc79 ("arm64: Add Broadcom Set Top Box Kconfig
entry point") we have ARCH_BRCMSTB also visible on ARM64 platform, yet
this reboot driver was not selectable, so fix that.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Assembly in at91_lpddr_poweroff has r0 in the clobber list but uses r6.
Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Assembly in at91_lpddr_poweroff has r0 in the clobber list but uses r6.
Reported-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Since we now support the standard 'input_current_limit' property by
commit 3fb319c2cd ("power: supply: twl4030-charger: add writable INPUT_CURRENT_LIMIT property")
we can now remove the nonstandard 'max_current' sysfs attribute.
See Documentation/power/power_supply_class.txt line 125
Both are functionally equivalent. From ABI point of view it is just a rename
of the property.
This also removes the entry in Documentation/ABI/testing/sysfs-class-power-twl4030
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
There are several cut and past bugs here. ltc3651_charger->charger is
NULL at this point, so we return success instead of the intended error
codes.
Fixes: c94d4ed017 ("power: supply: Add ltc3651-charger driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
[Wei Yongjun found the same issue independently]
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Acked-by: Mike Looijmans <mike.looijmans@topic.nl>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
This fixes the TODO to parse strings and convert them to enum values
when writing to a power_supply class property sysfs attribute.
There is at least one driver that has a writable enum property that
previously could only be written as an integer, so a fallback to writing
enums as integers instead of strings is provided so we don't break existing
userspace programs.
Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
Apple currently supports three very common USB chargers:
https://www.apple.com/power-adapters/
These chargers implement a proprietary Apple method for advertising
1A, 2.1A, and 2.4A at 5V called "Brick ID".
In addition, 3rd parties implement the same charging method in many
charging accessories that work with iOS devices.
Devices that have charger detection chips such as the Pericom PI3USB9281,
eg. Google Chromebook Pixel 2015, are capable of detecting
these chargers, so let's add a type to facilicate passing that info
up to userspace.
This adds a separate power supply type for Apple's proprietary
"Brick ID" charging method.
Signed-off-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
The PPC_DT_CPU_FTRs is a bit misplaced in menuconfig, it shows up with
other general kernel options. It's really more at home in the "Platform
Support" section, so move it there.
Also enable it by default, for Book3s 64. It does mostly nothing unless
the device tree properties are found, and we will want it enabled
eventually in distro kernels, so turn it on to start getting more
testing.
Fixes: 5a61ef74f2 ("powerpc/64s: Support new device tree binding for discovering CPU features")
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Supporting 512TB requires us to do a order 3 allocation for level 1 page
table (pgd). This results in page allocation failures with certain workloads.
For now limit 4k linux page size config to 64TB.
Fixes: f6eedbba7a ("powerpc/mm/hash: Increase VA range to 128TB")
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Fix error path if we can't copy user structure on CXL_IOCTL_START_WORK
ioctl. We shouldn't unlock the context status mutex as it was not
locked (yet).
Fixes: 0712dc7e73 ("cxl: Fix issues when unmapping contexts")
Cc: stable@vger.kernel.org # v3.19+
Signed-off-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Reviewed-by: Vaibhav Jain <vaibhav@linux.vnet.ibm.com>
Reviewed-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
When calling CEC_RECEIVE do not check if the adapter is configured.
Typically CEC_RECEIVE is called after a select() and if that indicates
that there are messages in the receive queue, then you should always be
able to dequeue a message.
The race condition here is that a message has been received and is
queued, so select() tells userspace that a message is available. But
before the application calls CEC_RECEIVE the adapter is unconfigured
(e.g. the HDMI cable is removed). Now select will always report that
there is a message, but calling CEC_RECEIVE will always return -ENONET
because the adapter is no longer configured and so will never actually
dequeue the message.
There is really no need for this check, and in fact the ENONET error
code was never documented for CEC_RECEIVE. This may have been a left-over
of old code that was never updated.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: <stable@vger.kernel.org> # for v4.10 and up
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
This reverts commit cf39bf58af.
The commit regression to users that define both console=ttyS1
and console=ttyS0 on the command line, see
https://lkml.kernel.org/r/20170509082915.GA13236@bistromath.localdomain
The kernel log messages always appeared only on one serial port. It is
even documented in Documentation/admin-guide/serial-console.rst:
"Note that you can only define one console per device type (serial,
video)."
The above mentioned commit changed the order in which the command line
parameters are searched. As a result, the kernel log messages go to
the last mentioned ttyS* instead of the first one.
We long thought that using two console=ttyS* on the command line
did not make sense. But then we realized that console= parameters
were handled also by systemd, see
http://0pointer.de/blog/projects/serial-console.html
"By default systemd will instantiate one serial-getty@.service on
the main kernel console, if it is not a virtual terminal."
where
"[4] If multiple kernel consoles are used simultaneously, the main
console is the one listed first in /sys/class/tty/console/active,
which is the last one listed on the kernel command line."
This puts the original report into another light. The system is running
in qemu. The first serial port is used to store the messages into a file.
The second one is used to login to the system via a socket. It depends
on systemd and the historic kernel behavior.
By other words, systemd causes that it makes sense to define both
console=ttyS1 console=ttyS0 on the command line. The kernel fix
caused regression related to userspace (systemd) and need to be
reverted.
In addition, it went out that the fix helped only partially.
The messages still were duplicated when the boot console was
removed early by late_initcall(printk_late_init). Then the entire
log was replayed when the same console was registered as a normal one.
Link: 20170606160339.GC7604@pathway.suse.cz
Cc: Aleksey Makarov <aleksey.makarov@linaro.org>
Cc: Sabrina Dubroca <sd@queasysnail.net>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Peter Hurley <peter@hurleysoftware.com>
Cc: Jiri Slaby <jslaby@suse.com>
Cc: Robin Murphy <robin.murphy@arm.com>,
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "Nair, Jayachandran" <Jayachandran.Nair@cavium.com>
Cc: linux-serial@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reported-by: Sabrina Dubroca <sd@queasysnail.net>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
* A multiplication for the size determination of a memory allocation
indicated that an array data structure should be processed.
Thus use the corresponding function "kcalloc".
This issue was detected by using the Coccinelle software.
* Replace the specification of a data structure by a pointer dereference
to make the corresponding size determination a bit safer according to
the Linux coding style convention.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Replace the specification of a data structure by a pointer dereference
as the parameter for the operator "sizeof" to make the corresponding size
determination a bit safer according to the Linux coding style convention.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>
We are now booting all mach-omap2 in device tree only mode.
Any code that is only called in legacy boot mode where
of_have_populated_dt() is not set is safe to remove now.
Note that omap_init_sti() won't do anything so we can
remove omap2_init_devices() as pointed out by Sebastian
Reichel <sebastian.reichel@collabora.co.uk>.
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>
We are now booting all mach-omap2 in device tree only mode.
Any code that is only called in legacy boot mode where
of_have_populated_dt() is not set is safe to remove now.
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>
We are now booting all mach-omap2 in device tree only mode.
Any code that is only called in legacy boot mode where
of_have_populated_dt() is not set is safe to remove now.
Note that the volt_data is still being used.
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>
On sparc, if we have an alloca() like situation, as is the case with
SHASH_DESC_ON_STACK(), we can end up referencing deallocated stack
memory. The result can be that the value is clobbered if a trap
or interrupt arrives at just the right instruction.
It only occurs if the function ends returning a value from that
alloca() area and that value can be placed into the return value
register using a single instruction.
For example, in lib/libcrc32c.c:crc32c() we end up with a return
sequence like:
return %i7+8
lduw [%o5+16], %o0 ! MEM[(u32 *)__shash_desc.1_10 + 16B],
%o5 holds the base of the on-stack area allocated for the shash
descriptor. But the return released the stack frame and the
register window.
So if an intererupt arrives between 'return' and 'lduw', then
the value read at %o5+16 can be corrupted.
Add a data compiler barrier to work around this problem. This is
exactly what the gcc fix will end up doing as well, and it absolutely
should not change the code generated for other cpus (unless gcc
on them has the same bug :-)
With crucial insight from Eric Sandeen.
Cc: <stable@vger.kernel.org>
Reported-by: Anatoly Pugachev <matorola@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
And prevent calling i915_ggtt_disable_guc twice (the first when GuC init
failed, and the second time during driver unload / intel_uc_fini_hw),
and hitting the GEM_BUG_ON.
v2: Clear enable_guc_loading unconditionally (Michal)
Make sure guc_free_load_err_log is still called (Daniele)
Don't shoot the messenger (Chris)
Fixes: 3950bf3dbf ("drm/i915/guc: Add onion teardown to the GuC
setup")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170605171251.9905-1-michel.thierry@intel.com
Now that RT-mutex has lockdep annotations, add them to the selftest.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
There is no such thing as a bad unlock order.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Now that (PI) futexes have their own private RT-mutex interface and
implementation we can easily add lockdep annotations to the existing
RT-mutex interface.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Since Will and me have rewritten and heavily extended the atomic*_t
infrastructure over the past few years, claim maintainership of it.
We would also like to add Boqun as he helped out with PowerPC and has shown
good understanding of these bits.
We would still defer to architecture maintainers on implementation
details, but we'd take care of the interface and cross architecture
semantics of the primitives.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20161108140603.GH3117@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
It is completely unused and implemented only on x86.
Remove it.
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170526172900.91058-1-dvyukov@google.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Deferrable vmstat_updater was missing in commit:
c1de45ca83 ("sched/idle: Add support for tasks that inject idle")
Add it back.
Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Aubrey Li <aubrey.li@intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1496803742-38274-1-git-send-email-aubrey.li@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The stop class is invoked through stop_machine only.
This is dead code on UP builds.
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170529210302.26868-3-nicolas.pitre@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
We have been facing some problems with self-suspending constrained
deadline tasks. The main reason is that the original CBS was not
designed for such sort of tasks.
One problem reported by Xunlei Pang takes place when a task
suspends, and then is awakened before the deadline, but so close
to the deadline that its remaining runtime can cause the task
to have an absolute density higher than allowed. In such situation,
the original CBS assumes that the task is facing an early activation,
and so it replenishes the task and set another deadline, one deadline
in the future. This rule works fine for implicit deadline tasks.
Moreover, it allows the system to adapt the period of a task in which
the external event source suffered from a clock drift.
However, this opens the window for bandwidth leakage for constrained
deadline tasks. For instance, a task with the following parameters:
runtime = 5 ms
deadline = 7 ms
[density] = 5 / 7 = 0.71
period = 1000 ms
If the task runs for 1 ms, and then suspends for another 1ms,
it will be awakened with the following parameters:
remaining runtime = 4
laxity = 5
presenting a absolute density of 4 / 5 = 0.80.
In this case, the original CBS would assume the task had an early
wakeup. Then, CBS will reset the runtime, and the absolute deadline will
be postponed by one relative deadline, allowing the task to run.
The problem is that, if the task runs this pattern forever, it will keep
receiving bandwidth, being able to run 1ms every 2ms. Following this
behavior, the task would be able to run 500 ms in 1 sec. Thus running
more than the 5 ms / 1 sec the admission control allowed it to run.
Trying to address the self-suspending case, Luca Abeni, Giuseppe
Lipari, and Juri Lelli [1] revisited the CBS in order to deal with
self-suspending tasks. In the new approach, rather than
replenishing/postponing the absolute deadline, the revised wakeup rule
adjusts the remaining runtime, reducing it to fit into the allowed
density.
A revised version of the idea is:
At a given time t, the maximum absolute density of a task cannot be
higher than its relative density, that is:
runtime / (deadline - t) <= dl_runtime / dl_deadline
Knowing the laxity of a task (deadline - t), it is possible to move
it to the other side of the equality, thus enabling to define max
remaining runtime a task can use within the absolute deadline, without
over-running the allowed density:
runtime = (dl_runtime / dl_deadline) * (deadline - t)
For instance, in our previous example, the task could still run:
runtime = ( 5 / 7 ) * 5
runtime = 3.57 ms
Without causing damage for other deadline tasks. It is note worthy
that the laxity cannot be negative because that would cause a negative
runtime. Thus, this patch depends on the patch:
df8eac8caf ("sched/deadline: Throttle a constrained deadline task activated after the deadline")
Which throttles a constrained deadline task activated after the
deadline.
Finally, it is also possible to use the revised wakeup rule for
all other tasks, but that would require some more discussions
about pros and cons.
Reported-by: Xunlei Pang <xpang@redhat.com>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
[peterz: replaced dl_is_constrained with dl_is_implicit]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luca Abeni <luca.abeni@santannapisa.it>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Romulo Silva de Oliveira <romulo.deoliveira@ufsc.br>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tommaso Cucinotta <tommaso.cucinotta@sssup.it>
Link: http://lkml.kernel.org/r/5c800ab3a74a168a84ee5f3f84d12a02e11383be.1495803804.git.bristot@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
