There are two DVB demux callbacks and ioctls that aren't documented
and aren't used at all by the DVB core or by any DVB driver upstream.
Let's comment out the code for those two ioctls and remove on some
future version.
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
There are a few inconsistencies between the old documentation
that got imported into the header and the current status.
Update them, and use the proper doc-nano nomenclature for
struct artuments "@", instead of foo().
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
The DocBook/media/dvb/kdapi.xml contains the description of
the kABI for DVB. The problem is that, by being maintained
on a separate file and not being updated for years, it got
outdated. So, for example, some callback parameters were
changed, but the DocBook were still using the old stuff.
As a first step to fix it, let's move the documentation of
struct dmx_demux into demux.h and fix the parameters used
there.
For now, don't document any other field nor touch the
descriptions that got moved, letting this job to other
patches. That makes easier to review the patch.
PS.: Please notice that an additional patch will be needed
in order to fix the return values (some uses non-existent
return codes) and to the functions and callbacks mentioned at
the descriptions.
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
There are several CodingStyle violations at the DVB code. While
we won't be fixing them as a hole, let's fix at least the
headers, as we're touching on them already in order to properly
document them.
No functional changes.
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
This struct is already documented at the header file, but it is
not using Kernel doc-nano format. Convert to it.
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
The function can return negative value, assigning it to unsigned
variable can cause memory corruption.
The problem has been detected using proposed semantic patch
scripts/coccinelle/tests/unsigned_lesser_than_zero.cocci [1].
[1]: http://permalink.gmane.org/gmane.linux.kernel/2038576
Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: kernel-janitors@vger.kernel.org
Link: http://lkml.kernel.org/r/1444122017-16856-1-git-send-email-a.hajda@samsung.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
The perf_hpp__init currently does not respect sorting dimensions and the
setup_sorting function could endup queueing same format twice. That
screwed up the perf_hpp__list and got stuck in loop within
perf_hpp__setup_output_field function.
$ perf report -F +overhead
0x00000000004c1355 in perf_hpp__is_sort_entry (format=format@entry=0x880440 <perf_hpp.format>) at util/sort.c:1506
1506 {
#0 0x00000000004c1355 in perf_hpp__is_sort_entry (format=format@entry=0x880440 <perf_hpp.format>) at util/sort.c:1506
#1 0x00000000004c139d in perf_hpp__same_sort_entry (a=a@entry=0x880440 <perf_hpp.format>, b=b@entry=0x2bb2fe0) at util/sort.c:1380
#2 0x00000000004f8d3c in perf_hpp__setup_output_field () at ui/hist.c:554
#3 0x00000000004c1d1e in setup_sorting () at util/sort.c:1984
#4 0x000000000042efbf in cmd_report (argc=0, argv=0x7ffea5a0e790, prefix=<optimized out>) at builtin-report.c:874
#5 0x0000000000476f13 in run_builtin (p=p@entry=0x875628 <commands+168>, argc=argc@entry=3, argv=argv@entry=0x7ffea5a0e790) at perf.c:385
#6 0x000000000047710b in handle_internal_command (argc=3, argv=0x7ffea5a0e790) at perf.c:445
#7 0x0000000000477176 in run_argv (argcp=argcp@entry=0x7ffea5a0e5fc, argv=argv@entry=0x7ffea5a0e5f0) at perf.c:489
#8 0x00000000004773e7 in main (argc=3, argv=0x7ffea5a0e790) at perf.c:606
Using hpp_dimension__add_output function to register the output column.
It will also mark the dimension as taken and omit above stuck.
Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1444134312-29136-4-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This function will allow to register output column from ui code and
respect taken sort/output dimensions.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1444134312-29136-3-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
There's no need to call reset_dimensions within __setup_output_field
function. It's already called in its caller setup_sorting right before
perf_hpp__init, which will be changed in following patch to respect
taken dimension.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1444134312-29136-2-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
In f309d44431 ("platform_device: better support builtin boilerplate
avoidance"), we introduced the builtin_driver() macro.
Here we use that support and extend it to PCI driver registration, so where
a driver is clearly non-modular and builtin-only, we can register it in a
similar fashion. Existing code that is clearly non-modular can be updated
with the simple mapping of
module_pci_driver(...) ---> builtin_pci_driver(...)
We've essentially cloned the former to make the latter, and taken out the
remove/module_exit parts since those never get used in a non-modular build
of the code.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Use a PWM lookup table to provide the PWM to the pwm-backlight device.
The driver has a legacy code path that is required only because boards
still use the legacy method of requesting PWMs by global ID. Replacing
these usages allows that legacy fallback to be removed.
Cc: Daniel Mack <daniel@zonque.org>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>
Cc: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Use a PWM lookup table to provide the PWM to the pwm-backlight device.
The driver has a legacy code path that is required only because boards
still use the legacy method of requesting PWMs by global ID. Replacing
these usages allows that legacy fallback to be removed.
Cc: Daniel Mack <daniel@zonque.org>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>
Cc: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
The ID and period for the backlight PWM are obtained from a PWM lookup
table, so the corresponding values don't need to be duplicated into the
platform data.
Cc: Daniel Mack <daniel@zonque.org>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>
Cc: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
Acked-by: Philipp Zabel <philipp.zabel@gmail.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
HDMI sinks are permitted to de-assert and re-assert the HPD signal to
indicate that their EDID has been updated, which may not involve a
change of video information.
An example of where such a situation can arise is when an AV receiver
is connected between the source and the display device. Events which
can cause the HPD to be deasserted include:
* turning on or switching to standby the AV receiver.
* turning on or switching to standby the display device.
Each of these can change the entire EDID data, or just a part of the
EDID data - it's up to the connected HDMI sink to do what they desire
here. For example
- with the AV receiver and display device both in standby, a source
connected to the AV receiver may provide its own EDID to the source.
- turning on the display device causes the display device's EDID to be
made available in an unmodified form to the source.
- subsequently turning on the AV receiver then provides a modified
version of the display device's EDID.
Moreover, HPD doesn't tell us whether something is actually listening
on the HDMI TDMS signals. The phy gives us a set of RXSENSE indications
which tell us whether there is a sink connected to the TMDS signals.
Currently, we use the HPD signal to enable or disable the HDMI block,
which is questionable when HPD is used in this manner. Using the
RXSENSE would be more appropriate, but there is some bad behaviour
which needs to be coped with. The iMX6 implementation lets the TMDS
signals float when the phy is "powered down", which cause spurious
interrupts. Rather than just using RXSENSE, use RXSENSE and HPD
becoming both active to signal the presence of a device, but loss
of RXSENSE to indicate that the device has been unplugged.
The side effect of this change is that a sink deasserting the HPD
signal to cause a re-read of the EDID data will not cause the bridge
to immediately disable the video signal.
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
When connected to HDMI sources, some DVI monitors de-assert their HPD
signal and TDMS loads for one seconds every four seconds when there is
no signal present on the connection.
Unfortunately, this behaviour is indistinguishable from a proper HDMI
setup with an AV receiver in the path to the display: the HDMI spec
requires us to detect HPD deassertions as short as 100ms, which indicate
that the EDID has changed.
Since it is possible to connect a DVI monitor to an AV receiver and then
to a HDMI source, merely working around this by detecting the lack of
HDMI vendor block in the EDID is insufficient - the AV receiver is at
liberty to modify the EDID as it sees fit, and it will place its own
parameters into the EDID including the HDMI vendor block.
DRM has support for forcing the state of a connector, which we should
implement to allow us to work around these broken DVI monitors - we can
tell DRM to force the connection state to indicate that there is always
a device connected to work around this problem. Although this requires
manual configuration, it is better than nothing at all.
When a forced connection state has been set, there is no point handling
our RXSENSE interrupts, so disable them in this circumstance.
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Add support for interlaced video modes to the dw_hdmi bridge. This
mainly involves halving the vertical parameters to be programmed into
the bridge registers, and setting the interlace_allowed connector flag.
This brings working 1080i support. However, 480i and 576i fail to
work due to the lack of proper pixel repetition support, which is not
trivial to add due to the tabular PLL parameterisation. Hence, we
filter out these modes in our mode_valid() method.
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
The support for interlaced video modes seems to be broken; we don't use
anything other than the vtotal/htotal from the timing information to
define the various sync counters.
Freescale patches for interlaced video support contain an alternative
sync counter setup, which we include here. This setup produces the
hsync and vsync via the normal counter 2 and 3, but moves the display
enable signal from counter 5 to counter 6. Therefore, we need to
change the display controller setup as well.
The corresponding Freescale patches for this change are:
iMX6-HDMI-support-interlaced-display-mode.patch
IPU-fine-tuning-the-interlace-display-timing-for-CEA.patch
This produces a working interlace format output from the IPU.
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Use a function to convert the sync pin to a bit mask for the DI_GENERAL
register, and move this out of the interlace/non-interlace path to the
common path.
Tested-by: Philipp Zabel <p.zabel@pengutronix.de>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
It's possible that the destination can be shadowed in userspace
(as, for example, the perf buffers are now). So we should take
care not to leak data that could be inspected by userspace.
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
arch/tile added word-at-a-time.h after the patch that added generic-y
entries; the generic-y entry is now stale.
arch/h8300 is newer than the generic-y patch for word-at-a-time.h,
and needs a generic-y entry.
arch/powerpc seems to have gotten a generic-y entry by mistake in
the first patch; this change removes it.
Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
The locktorture module has a list of torture types, and specifying
a type not on this list is supposed to cleanly fail the module load.
Unfortunately, the "fail" happens without the "cleanly". This commit
therefore adds the needed clean-up after an incorrect torture_type.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit allows --bootarg instead of --bootargs, --config instead of
--configs, and --qemu-arg instead of --qemu-args. For those cases where
a native English speaker might auto-correct the argument to be incorrect.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The torturing_tasks() function is used only in kernels built with
CONFIG_PROVE_RCU=y, so the second definition can result in unused-function
compiler warnings. This commit adds __maybe_unused to suppress these
warnings.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The rcutorture module has a list of torture types, and specifying a
type not on this list is supposed to cleanly fail the module load.
Unfortunately, the "fail" happens without the "cleanly". This commit
therefore adds the needed clean-up after an incorrect torture_type.
Reported-by: David Miller <davem@davemloft.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Miller <davem@davemloft.net>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
1. Rename __rcu_sync_is_idle() to rcu_sync_lockdep_assert() and
change it to use rcu_lockdep_assert().
2. Change rcu_sync_is_idle() to return rsp->gp_state == GP_IDLE
unconditonally, this way we can remove the same check from
rcu_sync_lockdep_assert() and clearly isolate the debugging
code.
Note: rcu_sync_enter()->wait_event(gp_state == GP_PASSED) needs
another CONFIG_PROVE_RCU check, the same as is done in ->sync(); but
this needs some simple preparations in the core RCU code to avoid the
code duplication.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Based on Peter Zijlstra's earlier patch.
Change percpu_down_read() to use __down_read(), this way we can
do rwsem_acquire_read() unconditionally at the start to make this
code more symmetric and clean.
Originally-From: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Update the comments broken by the previous change.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Currently down_write/up_write calls synchronize_sched_expedited()
twice, which is evil. Change this code to rely on rcu-sync primitives.
This avoids the _expedited "big hammer", and this can be faster in
the contended case or even in the case when a single thread does
down_write/up_write in a loop.
Of course, a single down_write() will take more time, but otoh it
will be much more friendly to the whole system.
To simplify the review this patch doesn't update the comments, fixed
by the next change.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This is the temporary ugly hack which will be reverted later. We only
need it to ensure that the next patch will not break "change sb_writers
to use percpu_rw_semaphore" patches routed via the VFS tree.
The alloc_super()->destroy_super() error path assumes that it is safe
to call percpu_free_rwsem() after kzalloc() without percpu_init_rwsem(),
so let's not disappoint it.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit allows rcu_sync structures to be safely deallocated,
The trick is to add a new ->wait field to the gp_ops array.
This field is a pointer to the rcu_barrier() function corresponding
to the flavor of RCU in question. This allows a new rcu_sync_dtor()
to wait for any outstanding callbacks before freeing the rcu_sync
structure.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The netdev checks recently added to RDMA CM expect a valid netdev to be
found for both InfiniBand and RoCE, but the code that find a netdev is
only implemented for InfiniBand.
Currently RoCE doesn't provide an API to find the netdev matching a
given set of parameters, so this patch just disables the netdev enforcement
for each incoming connections when the link layer is RoCE.
Fixes: 4c21b5bcef ("IB/cma: Add net_dev and private data checks to RDMA CM")
Reported-by: Kamal Heib <kamalh@mellanox.com>
Signed-off-by: Haggai Eran <haggaie@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
This commit validates that the caller of rcu_sync_is_idle() holds the
corresponding type of RCU read-side lock, but only in kernels built
with CONFIG_PROVE_RCU=y. This validation is carried out via a new
rcu_sync_ops->held() method that is checked within rcu_sync_is_idle().
Note that although this does add code to the fast path, it only does so
in kernels built with CONFIG_PROVE_RCU=y.
Suggested-by: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit adds the new struct rcu_sync_ops which holds sync/call
methods, and turns the function pointers in rcu_sync_struct into an array
of struct rcu_sync_ops. This simplifies the "init" helpers by collapsing
a switch statement and explicit multiple definitions into a simple
assignment and a helper macro, respectively.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The rcu_sync infrastructure can be thought of as infrastructure to be
used to implement reader-writer primitives having extremely lightweight
readers during times when there are no writers. The first use is in
the percpu_rwsem used by the VFS subsystem.
This infrastructure is functionally equivalent to
struct rcu_sync_struct {
atomic_t counter;
};
/* Check possibility of fast-path read-side operations. */
static inline bool rcu_sync_is_idle(struct rcu_sync_struct *rss)
{
return atomic_read(&rss->counter) == 0;
}
/* Tell readers to use slowpaths. */
static inline void rcu_sync_enter(struct rcu_sync_struct *rss)
{
atomic_inc(&rss->counter);
synchronize_sched();
}
/* Allow readers to once again use fastpaths. */
static inline void rcu_sync_exit(struct rcu_sync_struct *rss)
{
synchronize_sched();
atomic_dec(&rss->counter);
}
The main difference is that it records the state and only calls
synchronize_sched() if required. At least some of the calls to
synchronize_sched() will be optimized away when rcu_sync_enter() and
rcu_sync_exit() are invoked repeatedly in quick succession.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit moves cond_resched_rcu_qs() into stutter_wait(), saving
a line and also avoiding RCU CPU stall warnings from all torture
loops containing a stutter_wait().
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit adds percpu_rwsem tests based on the earlier rwsem tests.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit exports percpu_down_read(), percpu_down_write(),
__percpu_init_rwsem(), percpu_up_read(), and percpu_up_write() to allow
locktorture to test them when built as a module.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Real time mutexes is one of the few general primitives
that we do not have in locktorture. Address this -- a few
considerations:
o To spice things up, enable competing thread(s) to become
rt, such that we can stress different prio boosting paths
in the rtmutex code. Introduce a ->task_boost callback,
only used by rtmutex-torturer. Tasks will boost/deboost
around every 50k (arbitrarily) lock/unlock operations.
o Hold times are similar to what we have for other locks:
only occasionally having longer hold times (per ~200k ops).
So we roughly do two full rt boost+deboosting ops with
short hold times.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
There is no need to require LOCAL_DMA_LKEY support as the
PD allocation makes sure that there is a local_dma_lkey. Also
correctly set a return value in error path.
This caused a NULL pointer dereference in mlx5 which removed
the support for LOCAL_DMA_LKEY.
Fixes: bb6c96d728 ("xprtrdma: Replace global lkey with lkey local to PD")
Signed-off-by: Sagi Grimberg <sagig@mellanox.com>
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Acked-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
The recently added lockless_dereference() macro is not present in the
Documentation/ directory, so this commit fixes that.
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit rids the documentation of long-obsolete torture_type options
such as rcu_sync and adds new ones such as tasks. Also add verbiage
noting the fact that rcutorture now concurrently tests the asynchrounous,
synchronous, expedited synchronous, and polling grace-period primitives.
Reported-by: David Miller <davem@davemloft.net>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: David Miller <davem@davemloft.net>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
As there is lots of misinformation and outdated information on the
Internet about nearly all topics related to the kernel, I thought it
would be best if I based my RCU code on the guidelines of the examples
in the Documentation/ tree of the latest kernel. One thing that stuck
out when reading the whatisRCU.txt document was, "interesting how we
don't need any function to dereference rcu protected pointers when doing
updates if a lock is held. I wonder how static analyzers will work with
that." Then, a few weeks later, upon discovering sparse's __rcu support,
I ran it over my code, and lo and behold, things weren't done right.
Examining other RCU usages in the kernel reveal consistent usage of
rcu_dereference_protected, passing in lockdep_is_held as the
conditional. So, this patch adds that idiom to the documentation, so
that others ahead of me won't endure the same exercise.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The Linux kernel outputs copious text during boot, and a slow serial
console can result in stall warnings, particularly when messages are
printed with interrupts disabled. This commit adds this to the list
of causes of RCU CPU stall warning messages.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Documentation/memory-barriers.txt calls out RCU as one of the sets
of primitives associated with ACQUIRE and RELEASE. There really
is an association in that rcu_assign_pointer() includes a RELEASE
operation, but a quick read can convince people that rcu_read_lock() and
rcu_read_unlock() have ACQUIRE and RELEASE semantics, which they do not.
This commit therefore removes RCU from this list in order to avoid
this confusion.
Reported-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The various RCU list-deletion macros (list_del_rcu(),
hlist_del_init_rcu(), hlist_del_rcu(), hlist_bl_del_init_rcu(),
hlist_bl_del_rcu(), hlist_nulls_del_init_rcu(), and hlist_nulls_del_rcu())
do plain stores into the ->next pointer of the preceding list elemment.
Unfortunately, the compiler is within its rights to (for example) use
byte-at-a-time writes to update the pointer, which would fatally confuse
concurrent readers. This patch therefore adds the needed WRITE_ONCE()
macros.
KernelThreadSanitizer (KTSAN) reported the __hlist_del() issue, which
is a problem when __hlist_del() is invoked by hlist_del_rcu().
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The old rcu_lockdep_assert() was retained to ease handling of incoming
patches, but any use will result in deprecated warnings. However, its
replacement, RCU_LOCKDEP_WARN(), is now upstream. It is therefore
time to remove rcu_lockdep_assert(), which this commit does.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
The current list_entry_rcu() implementation copies the pointer to a stack
variable, then invokes rcu_dereference_raw() on it. This results in an
additional store-load pair. Now, most compilers will emit normal store
and load instructions, which might seem to be of negligible overhead,
but this results in a load-hit-store situation that can cause surprisingly
long pipeline stalls, even on modern microprocessors. The problem is
that it takes time for the store to get the store buffer updated, which
can delay the subsequent load, which immediately follows.
This commit therefore switches to the lockless_dereference() primitive,
which does not expect the __rcu annotations (that are anyway not present
in the list_head structure) and which, like rcu_dereference_raw(),
does not check for an enclosing RCU read-side critical section.
Most importantly, it does not copy the pointer, thus avoiding the
load-hit-store overhead.
Signed-off-by: Patrick Marlier <patrick.marlier@gmail.com>
[ paulmck: Switched to lockless_dereference() to suppress sparse warnings. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit adds an rcu_pointer_handoff() that is intended to mark
situations where a structure's protection transitions from RCU to some
other mechanism (locking, reference counting, whatever). These markings
should allow external tools to more easily spot bugs involving leaking
pointers out of RCU read-side critical sections.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit corrects the comment for the values of the ->gp_state field,
which previously incorrectly said that these were for the ->gp_flags
field.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
