The existing DSA binding has a number of limitations and problems. The
main problem is that it cannot represent a switch as a linux device,
hanging off some bus. It is limited to one CPU port. The DSA platform
device is artificial, and does not really represent hardware.
Implement a new binding which can be embedded into any type of node on
a bus to represent one switch device, and its links to other switches.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Replace the two switch statements with an array lookup, and store the
result in the dsa tree structure. The drivers no longer need to know
the selected tag protocol, so remove it from the dsa switch structure.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The new binding will not have a chip data structure, it will place the
routing directly into the switch structure. To enable backwards
compatibility, copy the routing from the chip data into the switch
structure.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
With a maximum of four switches, the size of the routing table is the
same as the pointer to it. Removing it makes the code simpler.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Move the port device node structure into the port structure, from the
chip data. This information is needed in the next step of implementing
the new binding.
The chip data structure is used while parsing the whole old binding,
before the individual switch structures exist. With the new bindings,
this is reversed, the switches exist first, and the interconnections
between the switches is derived from the individual switch
bindings. Thus this chip data structure becomes unneeded.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
eviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
There are going to be more per-port members added to the switch
structure. So add a port structure and move the netdev into it.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull Ceph fixes from Sage Weil:
"We have a few follow-up fixes for the libceph refactor from Ilya, and
then some cephfs + fscache fixes from Zheng.
The first two FS-Cache patches are acked by David Howells and deemed
trivial enough to go through our tree. The rest fix some issues with
the ceph fscache handling (disable cache for inodes opened for write,
and simplify the revalidation logic accordingly, dropping the
now-unnecessary work queue)"
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client:
ceph: use i_version to check validity of fscache
ceph: improve fscache revalidation
ceph: disable fscache when inode is opened for write
ceph: avoid unnecessary fscache invalidation/revlidation
ceph: call __fscache_uncache_page() if readpages fails
FS-Cache: make check_consistency callback return int
FS-Cache: wake write waiter after invalidating writes
libceph: use %s instead of %pE in dout()s
libceph: put request only if it's done in handle_reply()
libceph: change ceph_osdmap_flag() to take osdc
- Fix an incorrect check introduced by recent ACPICA changes which
causes problems with booting KVM guests to happen, among other
things (Lv Zheng).
- Fix a backlight issue introduced by recent changes to the ACPI
video driver (Aaron Lu).
- Fix the ACPI processor initialization which attempts to register
an IO region without checking if that really is necessary and
sometimes prevents drivers loaded subsequently from registering
their resources which leads to boot issues (Rafael Wysocki).
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Merge tag 'acpi-4.7-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull ACPI fixes from Rafael Wysocki:
"Two fixes for problems introduced recently (ACPICA and the ACPI
backlight driver) and one fix for an older issue that prevents at
least one system from booting.
Specifics:
- Fix an incorrect check introduced by recent ACPICA changes which
causes problems with booting KVM guests to happen, among other
things (Lv Zheng).
- Fix a backlight issue introduced by recent changes to the ACPI
video driver (Aaron Lu).
- Fix the ACPI processor initialization which attempts to register an
IO region without checking if that really is necessary and
sometimes prevents drivers loaded subsequently from registering
their resources which leads to boot issues (Rafael Wysocki)"
* tag 'acpi-4.7-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
ACPI / processor: Avoid reserving IO regions too early
ACPICA / Hardware: Fix old register check in acpi_hw_get_access_bit_width()
ACPI / Thermal / video: fix max_level incorrect value
Merge various fixes from Andrew Morton:
"10 fixes"
* emailed patches from Andrew Morton <akpm@linux-foundation.org>:
mm, page_alloc: recalculate the preferred zoneref if the context can ignore memory policies
mm, page_alloc: reset zonelist iterator after resetting fair zone allocation policy
mm, oom_reaper: do not use siglock in try_oom_reaper()
mm, page_alloc: prevent infinite loop in buffered_rmqueue()
checkpatch: reduce git commit description style false positives
mm/z3fold.c: avoid modifying HEADLESS page and minor cleanup
memcg: add RCU locking around css_for_each_descendant_pre() in memcg_offline_kmem()
mm: check the return value of lookup_page_ext for all call sites
kdump: fix dmesg gdbmacro to work with record based printk
mm: fix overflow in vm_map_ram()
Commit a91eb52abb ("qed: Revisit chain implementation") contains an
incorrect implementation for BE platforms, as device's regpairs containing
addresses are LE and they're not converted correctly when read back.
In addition, it raises a compilation warning for 32-bit platforms where
dma_addr_t is a 32-bit variable.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch adds in the ecore 2 new personalities in addition to
QED_PCI_ETH - QED_PCI_ISCSI and QED_PCI_ETH_ROCE.
Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This adds the qed portion of the RoCE & iSCSI firmware HSI,
as well as adding several new common HSI files which would be required
by both qed and qed* protocols.
Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
RoCE driver is going to need a 32-bit chain [current chain implementation
for qed* currently supports only 16-bit producer/consumer chains].
This patch adds said support, as well as doing other slight tweaks and
modifications to qed's chain API.
Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
SCTP has this pecualiarity that its packets cannot be just segmented to
(P)MTU. Its chunks must be contained in IP segments, padding respected.
So we can't just generate a big skb, set gso_size to the fragmentation
point and deliver it to IP layer.
This patch takes a different approach. SCTP will now build a skb as it
would be if it was received using GRO. That is, there will be a cover
skb with protocol headers and children ones containing the actual
segments, already segmented to a way that respects SCTP RFCs.
With that, we can tell skb_segment() to just split based on frag_list,
trusting its sizes are already in accordance.
This way SCTP can benefit from GSO and instead of passing several
packets through the stack, it can pass a single large packet.
v2:
- Added support for receiving GSO frames, as requested by Dave Miller.
- Clear skb->cb if packet is GSO (otherwise it's not used by SCTP)
- Added heuristics similar to what we have in TCP for not generating
single GSO packets that fills cwnd.
v3:
- consider sctphdr size in skb_gso_transport_seglen()
- rebased due to 5c7cdf339a ("gso: Remove arbitrary checks for
unsupported GSO")
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Tested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
skb_gso_network_seglen is not enough for checking fragment sizes if
skb is using GSO_BY_FRAGS as we have to check frag per frag.
This patch introduces skb_gso_validate_mtu, based on the former, which
will wrap the use case inside it as all calls to skb_gso_network_seglen
were to validate if it fits on a given TMU, and improve the check.
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Tested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This patch allows segmenting a skb based on its frags sizes instead of
based on a fixed value.
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Tested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Pull irq fixes from Thomas Gleixner:
- a few simple fixes for fallout from the recent gic-v3 changes
- a workaround for a Cavium thunderX erratum
- a bugfix for the pic32 irqchip to make external interrupts work proper
- a missing return value in the generic IPI management code
* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
irqchip/irq-pic32-evic: Fix bug with external interrupts.
irqchip/gicv3-its: numa: Enable workaround for Cavium thunderx erratum 23144
irqchip/gic-v3: Fix quiescence check in gic_enable_redist
irqchip/gic-v3: Fix copy+paste mistakes in defines
irqchip/gic-v3: Fix ICC_SGI1R_EL1.INTID decoding mask
genirq: Fix missing return value in irq_destroy_ipi()
Pull timer bugfix from Thomas Gleixner:
"A single bugfix for the error check wreckage we introduced in the
merge window"
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
time: Make settimeofday error checking work again
No architecture uses the genrtc driver any more, so let's kill it off
for good. This now also includes asm-generic/rtc.h, which is otherwise
completely unused.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Drivers should not really include stuff from asm-generic directly,
and the PC-style cmos rtc driver does this in order to reuse the
mc146818 implementation of get_rtc_time/set_rtc_time rather than
the architecture specific one for the architecture it gets built for.
To make it more obvious what is going on, this moves and renames the
two functions into include/linux/mc146818rtc.h, which holds the
other mc146818 specific code. Ideally it would be in a .c file,
but that would require extra infrastructure as the functions are
called by multiple drivers with conflicting dependencies.
With this change, the asm-generic/rtc.h header also becomes much
more generic, so it can be reused more easily across any architecture
that still relies on the genrtc driver.
The only caller of the internal __get_rtc_time/__set_rtc_time
functions is in arch/alpha/kernel/rtc.c, and we just change those
over to the new naming.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Per the discussion with Joonsoo Kim [1], we need check the return value
of lookup_page_ext() for all call sites since it might return NULL in
some cases, although it is unlikely, i.e. memory hotplug.
Tested with ltp with "page_owner=0".
[1] http://lkml.kernel.org/r/20160519002809.GA10245@js1304-P5Q-DELUXE
[akpm@linux-foundation.org: fix build-breaking typos]
[arnd@arndb.de: fix build problems from lookup_page_ext]
Link: http://lkml.kernel.org/r/6285269.2CksypHdYp@wuerfel
[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1464023768-31025-1-git-send-email-yang.shi@linaro.org
Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Just fallout from switching from asciidoc to sphinx/rst.
v2: Found more. Also s/\//#/ in the vgpu ascii-art - sphinx treats
those as comments and switch to variable-width, which wreaks the
layout.
v3: Undo some of the hacks, rebasing onto latest version of Jani's
series fixed it.
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Apparently not everyone has been super dutiful with updating this
stuff.
I still decided to leave out the documentation for all the *_property
pointers we have in drm_mode_config.
v2: Feedback from Liviu.
Acked-by: Liviu Dudau <Liviu.Dudau@arm.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Move the contents of the video/omapdss.h header file to omapdrm/dss local
header file and remove the original global header. The omapfb stach is
using video/omapfb_dss.h so this change will complete the separation of the
two driver implementation.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Copy the content of video/omapdss.h to a new (video/omapfb_dss.h) header
file and convert the omapfb drivers to use this new file.
The new header file is needed to complete the separation of omapdrm and
omapfb implementation of DSS.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Clean up the header files regarding to hdmi audio so the omap-hdmi-audio.h
file will only need to include the platform_data/omapdss.h file.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
CC: Mark Brown <broonie@kernel.org>
CC: Jyri Sarha <jsarha@ti.com>
CC: Liam Girdwood <liam.r.girdwood@linux.intel.com>
The num_devices, **devices and *default_device is leftover from the past.
They can be removed as they are no used.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
The driver only supports composite connection when booted in legacy mode
so the omap_dss_venc_type can be dropped from the pdata.
At the same time the video/omapdss.h include can be removed as it is no
longer needed.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
The panel is not used by any legacy board files so the legacy (pdata) boot
support can be dropped.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
The panel is not used by any legacy board files so the legacy (pdata) boot
support can be dropped.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
The panel is not used by any legacy board files so the legacy (pdata) boot
support can be dropped.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
The panel is not used by any legacy board files so the legacy (pdata) boot
support can be dropped.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
The panel is not used by any legacy board files so the legacy (pdata) boot
support can be dropped.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
The panel is not used by any legacy board files so the legacy (pdata) boot
support can be dropped.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
The panel is not used by any legacy board files so the legacy (pdata) boot
support can be dropped.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
The panel is not used by any legacy board files so the legacy (pdata) boot
support can be dropped.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
The panel is not used by any legacy board files so the legacy (pdata) boot
support can be dropped.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
The omap_display_init() is implemented in the mach-omap2/display.c so the
declaration should have been there as well.
Change the board files to include display.h to avoid build breakage at the
same time.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
commit 93c667ca25
("of: *node argument to of_parse_phandle_with_args should be const")
changed to const for struct device node *np,
but it cares CONFIG_OF case only, !CONFIG_OF case need it too.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Rob Herring <robh@kernel.org>
lockless_dereference() is planned to grow a sanity check to ensure
that the input parameter is a pointer. __ref_is_percpu() passes in an
unsinged long value which is a combination of a pointer and a flag.
While it can be casted to a pointer lvalue, the casting looks messy
and it's a special case anyway. Let's revert back to open-coding
READ_ONCE() and explicit barrier.
This doesn't cause any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Pranith Kumar <bobby.prani@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-team@fb.com
Link: http://lkml.kernel.org/g/20160522185040.GA23664@p183.telecom.by
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This patch allows device drivers to initialize more than one reserved
memory region assigned to given device. When driver needs to use more
than one reserved memory region, it should allocate child devices and
initialize regions by index for each of its child devices.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Add a helper function for device drivers to set DMA's max_seg_size.
Setting it to largest possible value lets DMA-mapping API always create
contiguous mappings in DMA address space. This is essential for all
devices, which use dma-contig videobuf2 memory allocator and shared
buffers.
Till now, the only case when vb2-dma-contig really 'worked' was a case
where userspace provided USERPTR buffer, which was in fact mmaped
contiguous buffer from the other v4l2/drm device. Also DMABUF made of
contiguous buffer worked only when its exporter did not split it into
several chunks in the scatter-list. Any other buffer failed, regardless
of the arch/platform used and the presence of the IOMMU of the device bus.
This patch provides interface to fix this issue.
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Commit:
78ce248faa ("efi: Iterate over efi.memmap in for_each_efi_memory_desc()")
introduced a regression for systems booted with the 'noefi' kernel option.
In particular, I observed an early kernel hang in efi_find_mirror()'s
for_each_efi_memory_desc() call. As we don't have efi memmap on this
system we enter this iterator with the following parameters:
efi.memmap.map = 0, efi.memmap.map_end = 0, efi.memmap.desc_size = 28
... then for_each_efi_memory_desc_in_map() does the following comparison:
(md) <= (efi_memory_desc_t *)((m)->map_end - (m)->desc_size);
... where md = 0, (m)->map_end = 0 and (m)->desc_size = 28 but when we subtract
something from a NULL pointer wrap around happens and we end up returning
invalid pointer and crash.
Fix it by using the correct pointer arithmetics.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mark Salter <msalter@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Fixes: 78ce248faa ("efi: Iterate over efi.memmap in for_each_efi_memory_desc()")
Link: http://lkml.kernel.org/r/1464690224-4503-2-git-send-email-matt@codeblueprint.co.uk
[ Made the changelog more readable. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Add a way to show different sysfs events attributes depending on
HyperThreading is on or off. This is difficult to determine
early at boot, so we just do it dynamically when the sysfs
attribute is read.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: acme@kernel.org
Cc: jolsa@kernel.org
Link: http://lkml.kernel.org/r/1463703002-19686-3-git-send-email-andi@firstfloor.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
The perf_event_aux() function iterates all PMUs and all events in
their respective per-CPU contexts to find the events to deliver
side-band records to.
For example, the brk test case in lkp triggers many mmap() operations,
which, if we're also running perf, results in many perf_event_aux()
invocations.
If we enable uncore PMU support (even when uncore events are not used),
dozens of uncore PMUs will be iterated, which can significantly
decrease brk_test's throughput.
For example, the brk throughput:
without uncore PMUs: 2647573 ops_per_sec
with uncore PMUs: 1768444 ops_per_sec
... a 33% reduction.
To get at the per-CPU events that need side-band records, this patch
puts these events on a per-CPU list, this avoids iterating the PMUs
and any events that do not need side-band records.
Per task events are unchanged to avoid extra overhead on the context
switch paths.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reported-by: Huang, Ying <ying.huang@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1458757477-3781-1-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Generally task_struct is only protected by RCU if it was found on a
RCU protected list (say, for_each_process() or find_task_by_vpid()).
As Kirill pointed out rq->curr isn't protected by RCU, the scheduler
drops the (potentially) last reference without RCU gp, this means
that we need to fix the code which uses foreign_rq->curr under
rcu_read_lock().
Add a new helper which can be used to dereference rq->curr or any
other pointer to task_struct assuming that it should be cleared or
updated before the final put_task_struct(). It returns non-NULL
only if this task can't go away before rcu_read_unlock().
( Also add try_get_task_struct() to make it easier to use this API
correctly. )
Suggested-by: Kirill Tkhai <ktkhai@parallels.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
[ Updated comments; added try_get_task_struct()]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>
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>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Link: http://lkml.kernel.org/r/20160518170218.GY3192@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Commit 50755bc1c3 ("seqlock: fix raw_read_seqcount_latch()") broke
raw_read_seqcount_latch().
If you look at the comment that was modified; the thing that changes is
the seq count, not the latch pointer.
* void latch_modify(struct latch_struct *latch, ...)
* {
* smp_wmb(); <- Ensure that the last data[1] update is visible
* latch->seq++;
* smp_wmb(); <- Ensure that the seqcount update is visible
*
* modify(latch->data[0], ...);
*
* smp_wmb(); <- Ensure that the data[0] update is visible
* latch->seq++;
* smp_wmb(); <- Ensure that the seqcount update is visible
*
* modify(latch->data[1], ...);
* }
*
* The query will have a form like:
*
* struct entry *latch_query(struct latch_struct *latch, ...)
* {
* struct entry *entry;
* unsigned seq, idx;
*
* do {
* seq = lockless_dereference(latch->seq);
So here we have:
seq = READ_ONCE(latch->seq);
smp_read_barrier_depends();
Which is exactly what we want; the new code:
seq = ({ p = READ_ONCE(latch);
smp_read_barrier_depends(); p })->seq;
is just wrong; because it looses the volatile read on seq, which can now
be torn or worse 'optimized'. And the read_depend barrier is also placed
wrong, we want it after the load of seq, to match the above data[]
up-to-date wmb()s.
Such that when we dereference latch->data[] below, we're guaranteed to
observe the right data.
*
* idx = seq & 0x01;
* entry = data_query(latch->data[idx], ...);
*
* smp_rmb();
* } while (seq != latch->seq);
*
* return entry;
* }
So yes, not passing a pointer is not pretty, but the code was correct,
and isn't anymore now.
Change to explicit READ_ONCE()+smp_read_barrier_depends() to avoid
confusion and allow strict lockless_dereference() checking.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 50755bc1c3 ("seqlock: fix raw_read_seqcount_latch()")
Link: http://lkml.kernel.org/r/20160527111117.GL3192@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
