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This commit adds discussion of address and data dependencies to the
beginning of rcu_dereference.rst in order to enable readers to more
easily make the connection to the Linux-kernel memory model in general
and to memory-barriers.txt in particular.
Reported-by: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>
Reported-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
Currently, the reader/updater compatibility rules for the three RCU
Tasks flavors are squished together in a single paragraph, which can
result in confusion. This commit therefore splits them out into a list,
clearly showing the distinction between these flavors.
Link: https://lore.kernel.org/all/20231002211936.5948253e@gandalf.local.home/
Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
Remove the repeated word "of" in comments.
Signed-off-by: Charles Han <hanchunchao@inspur.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
rcu_report_dead() and rcutree_migrate_callbacks() have their headers in
rcupdate.h while those are pure rcutree calls, like the other CPU-hotplug
functions.
Also rcu_cpu_starting() and rcu_report_dead() have different naming
conventions while they mirror each other's effects.
Fix the headers and propose a naming that relates both functions and
aligns with the prefix of other rcutree CPU-hotplug functions.
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
This function is gone since:
53b46303da (rcu: Remove rsp parameter from rcu_boot_init_percpu_data() and friends)
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
More explicitly state what is, and what is not guaranteed to those
who iterate a list while protected by RCU.
[ paulmck: Apply Joel Fernandes feedback. ]
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
The example code snippets on rculist_nulls.rst are assuming 'obj' to
have the 'hlist_head' or 'hlist_nulls_head' field named 'obj_node', but
a sentence and some code snippets are wrongly calling
'obj->obj_node.next' as 'obj->obj_next', or 'obj->obj_node' as 'member'.
Fix it.
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The type of 'obj' in example code of rculist_nulls.rst is implicit.
Provide the specific type of it before the example code.
Suggested-by: Paul E. McKenney <paulmck@kernel.org>
Link: https://lore.kernel.org/rcu/43943609-f80c-4b6a-9844-994eef800757@paulmck-laptop/
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Lookup example code snippets in rculist_nulls.rst are using 'obj'
without assignment. Fix the code to assign it properly.
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Lookup example of non-hlist_nulls management is missing a semicolon, and
having inconsistent indentation (one line is using single space
indentation while others are using two spaces indentation). Fix the
trivial issues.
Signed-off-by: SeongJae Park <sj@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
We should exit the RCU read-side critical section before re-entering.
Signed-off-by: Alan Huang <mmpgouride@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Since there are now exactly _zero_ users of RCU_NONIDLE(), make it go
away before someone else decides to (ab)use it.
[ paulmck: Remove extraneous whitespace. ]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The kfree_rcu() macro is deprecated. Rename it to its new
kfree_rcu_mightsleep() name in this documentation.
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Correct spelling problems for Documentation/RCU/ as reported
by codespell.
Note: in RTFP.txt, there are other misspellings that are left as is
since they were used that way in email Subject: lines or in LWN.net
articles. [preemptable, Preemptable, synchonisation]
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Frederic Weisbecker <frederic@kernel.org>
Cc: Neeraj Upadhyay <quic_neeraju@quicinc.com>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: rcu@vger.kernel.org
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
"Please not that you *cannot* rely..." has a typo.
Fix it.
Acked-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Qiuxu Zhuo <qiuxu.zhuo@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Documentation/RCU/stallwarn.rst:
401: WARNING: Literal block expected; none found.
428: WARNING: Literal block expected; none found.
445: WARNING: Literal block expected; none found.
459: WARNING: Literal block expected; none found.
468: WARNING: Literal block expected; none found.
The literal block needs to be indented, so this commit adds two spaces
to each line.
In addition, ':', which is used as a boundary in the literal block, is
replaced by '|'.
Link: https://lore.kernel.org/linux-next/20221123163255.48653674@canb.auug.org.au/
Fixes: 3d2788ba4573 ("doc: Document CONFIG_RCU_CPU_STALL_CPUTIME=y stall information")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Tested-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Line numbers in code snippets in rcubarrier.rst have beed left adjusted
since commit 4af498306f ("doc: Convert to rcubarrier.txt to ReST").
This might have been because right adjusting them had confused Sphinx.
The rules around a literal block in reST are:
- Need a blank line above it.
- A line with the same indent level as the line above it is regarded
as the end of it.
Those line numbers can be right adjusted by keeping indents at two-
digit numbers. While at it, add some spaces between the column of line
numbers and the code area for better readability.
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit documents the additional RCU CPU stall warning output
produced by kernels built with CONFIG_RCU_CPU_STALL_CPUTIME=y or booted
with rcupdate.rcu_cpu_stall_cputime=1.
[ paulmck: Apply wordsmithing. ]
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit updates UP.rst to reflect changes over the past few years,
including the advent of userspace RCU libraries for constrained systems.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit updates rcu_dereference.rst to reflect RCU additions and
changes over the past few years
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit updates rcubarrier.txt to reflect RCU additions and changes
over the past few years.
[ paulmck: Apply Stephen Rothwell feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit updates NMI-RCU.rst to highlight the ancient heritage of
the example code and to discourage wanton compiler "optimizations".
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
- Core:
- The timer_shutdown[_sync]() infrastructure:
Tearing down timers can be tedious when there are circular
dependencies to other things which need to be torn down. A prime
example is timer and workqueue where the timer schedules work and the
work arms the timer.
What needs to prevented is that pending work which is drained via
destroy_workqueue() does not rearm the previously shutdown
timer. Nothing in that shutdown sequence relies on the timer being
functional.
The conclusion was that the semantics of timer_shutdown_sync() should
be:
- timer is not enqueued
- timer callback is not running
- timer cannot be rearmed
Preventing the rearming of shutdown timers is done by discarding rearm
attempts silently. A warning for the case that a rearm attempt of a
shutdown timer is detected would not be really helpful because it's
entirely unclear how it should be acted upon. The only way to address
such a case is to add 'if (in_shutdown)' conditionals all over the
place. This is error prone and in most cases of teardown not required
all.
- The real fix for the bluetooth HCI teardown based on
timer_shutdown_sync().
A larger scale conversion to timer_shutdown_sync() is work in
progress.
- Consolidation of VDSO time namespace helper functions
- Small fixes for timer and timerqueue
- Drivers:
- Prevent integer overflow on the XGene-1 TVAL register which causes
an never ending interrupt storm.
- The usual set of new device tree bindings
- Small fixes and improvements all over the place
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Merge tag 'timers-core-2022-12-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer updates from Thomas Gleixner:
"Updates for timers, timekeeping and drivers:
Core:
- The timer_shutdown[_sync]() infrastructure:
Tearing down timers can be tedious when there are circular
dependencies to other things which need to be torn down. A prime
example is timer and workqueue where the timer schedules work and
the work arms the timer.
What needs to prevented is that pending work which is drained via
destroy_workqueue() does not rearm the previously shutdown timer.
Nothing in that shutdown sequence relies on the timer being
functional.
The conclusion was that the semantics of timer_shutdown_sync()
should be:
- timer is not enqueued
- timer callback is not running
- timer cannot be rearmed
Preventing the rearming of shutdown timers is done by discarding
rearm attempts silently.
A warning for the case that a rearm attempt of a shutdown timer is
detected would not be really helpful because it's entirely unclear
how it should be acted upon. The only way to address such a case is
to add 'if (in_shutdown)' conditionals all over the place. This is
error prone and in most cases of teardown not required all.
- The real fix for the bluetooth HCI teardown based on
timer_shutdown_sync().
A larger scale conversion to timer_shutdown_sync() is work in
progress.
- Consolidation of VDSO time namespace helper functions
- Small fixes for timer and timerqueue
Drivers:
- Prevent integer overflow on the XGene-1 TVAL register which causes
an never ending interrupt storm.
- The usual set of new device tree bindings
- Small fixes and improvements all over the place"
* tag 'timers-core-2022-12-10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (34 commits)
dt-bindings: timer: renesas,cmt: Add r8a779g0 CMT support
dt-bindings: timer: renesas,tmu: Add r8a779g0 support
clocksource/drivers/arm_arch_timer: Use kstrtobool() instead of strtobool()
clocksource/drivers/timer-ti-dm: Fix missing clk_disable_unprepare in dmtimer_systimer_init_clock()
clocksource/drivers/timer-ti-dm: Clear settings on probe and free
clocksource/drivers/timer-ti-dm: Make timer_get_irq static
clocksource/drivers/timer-ti-dm: Fix warning for omap_timer_match
clocksource/drivers/arm_arch_timer: Fix XGene-1 TVAL register math error
clocksource/drivers/timer-npcm7xx: Enable timer 1 clock before use
dt-bindings: timer: nuvoton,npcm7xx-timer: Allow specifying all clocks
dt-bindings: timer: rockchip: Add rockchip,rk3128-timer
clockevents: Repair kernel-doc for clockevent_delta2ns()
clocksource/drivers/ingenic-ost: Define pm functions properly in platform_driver struct
clocksource/drivers/sh_cmt: Access registers according to spec
vdso/timens: Refactor copy-pasted find_timens_vvar_page() helper into one copy
Bluetooth: hci_qca: Fix the teardown problem for real
timers: Update the documentation to reflect on the new timer_shutdown() API
timers: Provide timer_shutdown[_sync]()
timers: Add shutdown mechanism to the internal functions
timers: Split [try_to_]del_timer[_sync]() to prepare for shutdown mode
...
In order to make sure that a timer is not re-armed after it is stopped
before freeing, a new shutdown state is added to the timer code. The API
timer_shutdown_sync() and timer_shutdown() must be called before the
object that holds the timer can be freed.
Update the documentation to reflect this new workflow.
[ tglx: Updated to the new semantics and updated the zh_CN version ]
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Link: https://lore.kernel.org/r/20221110064147.712934793@goodmis.org
Link: https://lore.kernel.org/r/20221123201625.375284489@linutronix.de
Adjust to the new preferred function names.
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
Link: https://lore.kernel.org/r/20221123201625.075320635@linutronix.de
This commit updates listRCU.txt to reflect RCU additions and changes
over the past few years.
[ paulmck: Apply kernel test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Although RCU can in theory be used to protect array indexes in a manner
similar to the way it protects pointers, doing so is extremely risky
because of the huge number of optimizations that modern compilers can
apply to integral types.
For but one example, if your code can be configured such that your array
contains only a single element, then indexing that array with any integer
other than zero invokes undefined behavior, which in turn means that
the compiler is within its rights to assume (without checking!) that any
integer used as an index to that array has the value zero. Therefore,
the compiler can index the array with the constant zero, which breaks
any dependencies that might have otherwise existed between the time the
actual value was loaded and the time that the array was indexed.
This commit therefore removes the arrayRCU.rst file that describes how
to go about carrying dependencies through array indexes.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
but a few significant changes even so:
- A complete rewriting of the top-level index.rst file, which mostly
reflects itself in a redone top page in the HTML-rendered docs. The hope
is that the new organization will be a friendlier starting point for
both users and developers.
- Some math-rendering improvements.
- A coding-style.rst update on the use of BUG() and WARN()
- A big maintainer-PHP guide update.
- Some code-of-conduct updates
- More Chinese translation work
Plus the usual pile of typo fixes, corrections, and updates.
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Merge tag 'docs-6.1' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet:
"There's not a huge amount of activity in the docs tree this time
around, but a few significant changes even so:
- A complete rewriting of the top-level index.rst file, which mostly
reflects itself in a redone top page in the HTML-rendered docs. The
hope is that the new organization will be a friendlier starting
point for both users and developers.
- Some math-rendering improvements.
- A coding-style.rst update on the use of BUG() and WARN()
- A big maintainer-PHP guide update.
- Some code-of-conduct updates
- More Chinese translation work
Plus the usual pile of typo fixes, corrections, and updates"
* tag 'docs-6.1' of git://git.lwn.net/linux: (66 commits)
checkpatch: warn on usage of VM_BUG_ON() and other BUG variants
coding-style.rst: document BUG() and WARN() rules ("do not crash the kernel")
Documentation: devres: add missing IO helper
Documentation: devres: update IRQ helper
Documentation/mm: modify page_referenced to folio_referenced
Documentation/CoC: Reflect current CoC interpretation and practices
docs/doc-guide: Add documentation on SPHINX_IMGMATH
docs: process/5.Posting.rst: clarify use of Reported-by: tag
docs, kprobes: Fix the wrong location of Kprobes
docs: add a man-pages link to the front page
docs: put atomic*.txt and memory-barriers.txt into the core-api book
docs: move asm-annotations.rst into core-api
docs: remove some index.rst cruft
docs: reconfigure the HTML left column
docs: Rewrite the front page
docs: promote the title of process/index.rst
Documentation: devres: add missing SPI helper
Documentation: devres: add missing PINCTRL helpers
docs: hugetlbpage.rst: fix a typo of hugepage size
docs/zh_CN: Add new translation of admin-guide/bootconfig.rst
...
This patch adds LWN articles about RCU APIs which were released in 2019.
Also, HTTP URLs are replaced by HTTPS.
Signed-off-by: Shao-Tse Hung <ccs100203@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Because the SLAB_TYPESAFE_BY_RCU code does not zero pages that are
to be broken up into slabs, the memory returned by kmem_cache_alloc()
must be fully initialized, including any spinlocks included in the newly
allocated structure. This means that readers attempting to look up an
SLAB_TYPESAFE_BY_RCU object must use a reference-counting approach.
A spinlock may be acquired only after a reference is obtained, which
prevents that object from being passed to kmem_struct_free(), but only
while that reference continues to be held.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit updates the rcu_access_pointer() advice, noting that its
return value should not be assigned to a local variable, and also noting
that there is little point in using rcu_access_pointer() within an RCU
read-side critical section.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The rcu_access_pointer() macro does not consult lockdep by design because
it is intended to be used outside of RCU read-side critical sections.
This commit therefore makes a separate list for it in whatisRCU.rst.
Similarly, RCU_LOCKDEP_WARN(), rcu_sleep_check(), and RCU_NONIDLE()
do not do anything with pointer access. This commit therefore creates
a separate utility-API list for them.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The checklist.rst document advises periodic synchronize_rcu() invocations
to prevent callback flooding. However, rcu_barrier() is often a better
choice. This commit therefore adds words to this effect.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
The current checklist.rst file correctly notes that RCU callbacks execute
in BH context, and cannot block. This commit adds words advising people
needing callbacks to block to use workqueues, for example, by replacing
call_rcu() with queue_rcu_work().
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit updates checklist.rst to emphasize the need for explicit
markers for RCU read-side critical sections.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
