Boot-time processing often loops in the kernel longer than one might
prefer, which can prevent expedited grace periods from completing in
a timely manner.  This in turn triggers a splat In nohz_full CPUs  One
could argue that long-looping code should be fixed, but on the other hand,
boot time is a bit special.

This commit therefore removes the splat.  Later commits will add the
splat back in, but in a way that removes false positives.
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Merge branches 'doc.2019.12.10a', 'exp.2019.12.09a', 'fixes.2020.01.24a', 'kfree_rcu.2020.01.24a', 'list.2020.01.10a', 'preempt.2020.01.24a' and 'torture.2019.12.09a' into HEAD

doc.2019.12.10a: Documentations updates
exp.2019.12.09a: Expedited grace-period updates
fixes.2020.01.24a: Miscellaneous fixes
kfree_rcu.2020.01.24a: Batch kfree_rcu() work
list.2020.01.10a: RCU-protected-list updates
preempt.2020.01.24a: Preemptible RCU updates
torture.2019.12.09a: Torture-test updates

Long ago, RCU used the stop-machine mechanism to implement expedited
grace periods, but no longer does so.  This commit therefore removes
the no-longer-needed #includes of linux/stop_machine.h.

Link: https://lwn.net/Articles/805317/Reported-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

'read_barrier_depends()' doesn't exist anymore so stop talking about it.
Signed-off-by: Will Deacon <will@kernel.org>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

[ paulmck: Apply Florian Fainelli feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

The ->srcu_last_gp_end field is accessed from any CPU at any time
by synchronize_srcu(), so non-initialization references need to use
READ_ONCE() and WRITE_ONCE().  This commit therefore makes that change.

Reported-by: syzbot+08f3e9d26e5541e1ecf2@syzkaller.appspotmail.com
Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Currently, force_qs_rnp() uses a for_each_leaf_node_possible_cpu()
loop containing a check of the current CPU's bit in ->qsmask.
This works, but this commit saves three lines by instead using
for_each_leaf_node_cpu_mask(), which combines the functionality of
for_each_leaf_node_possible_cpu() and leaf_node_cpu_bit().  This commit
also replaces the use of the local variable "bit" with rdp->grpmask.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit moves the rcu_{expedited,normal} definitions from
kernel/rcu/update.c to include/linux/rcupdate.h to make sure they are
in sync, and also to avoid the following warning from sparse:

kernel/ksysfs.c:150:5: warning: symbol 'rcu_expedited' was not declared. Should it be static?
kernel/ksysfs.c:167:5: warning: symbol 'rcu_normal' was not declared. Should it be static?
Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Only tree_stall.h needs to get name from GP state, so this commit
moves the gp_state_names[] array and the gp_state_getname()
from kernel/rcu/tree.h and kernel/rcu/tree.c, respectively, to
kernel/rcu/tree_stall.h.  While moving gp_state_names[], this commit
uses the GCC syntax to ensure that the right string is associated with
the right CPP macro.
Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

The call_rcu() function is an external RCU API that is declared in
include/linux/rcupdate.h.  There is thus no point in redeclaring it
in kernel/rcu/tree.h, so this commit removes that redundant declaration.
Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

In the call to trace_rcu_utilization() at the start of the loop in
rcu_cpu_kthread(), "rcu_wait" is incorrect, plus this trace event needs
to be hoisted above the loop to balance with either the "rcu_wait" or
"rcu_yield", depending on how the loop exits.  This commit therefore
makes these changes.
Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

The C preprocessor macros SRCU and TINY_RCU should instead be CONFIG_SRCU
and CONFIG_TINY_RCU, respectively in the #f in kernel/rcu/rcu.h. But
there is no harm when "TINY_RCU" is wrongly used, which are always
non-defined, which makes "!defined(TINY_RCU)" always true, which means
the code block is always included, and the included code block doesn't
cause any compilation error so far in CONFIG_TINY_RCU builds.  It is
also the reason this change should not be taken in -stable.

This commit adds the needed "CONFIG_" prefix to both macros.

Not for -stable.
Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

In the current code, rcu_nmi_enter_common() might decide to turn on
the tick using tick_dep_set_cpu(), but be delayed just before doing so.
Then the grace-period kthread might notice that the CPU in question had
in fact gone through a quiescent state, thus turning off the tick using
tick_dep_clear_cpu().  The later invocation of tick_dep_set_cpu() would
then incorrectly leave the tick on.

This commit therefore enlists the aid of the leaf rcu_node structure's
->lock to ensure that decisions to enable or disable the tick are
carried out before they can be reversed.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit provides wrapper functions for uses of ->rcu_read_lock_nesting
to improve readability and to ease future changes to support inlining
of __rcu_read_lock() and __rcu_read_unlock().
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

The rcu_node structure's ->expmask field is updated only when holding the
->lock, but is also accessed locklessly.  This means that all ->expmask
updates must use WRITE_ONCE() and all reads carried out without holding
->lock must use READ_ONCE().  This commit therefore changes the lockless
->expmask read in rcu_read_unlock_special() to use READ_ONCE().

Reported-by: syzbot+99f4ddade3c22ab0cf23@syzkaller.appspotmail.com
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Marco Elver <elver@google.com>

In rcu_preempt_deferred_qs_irqrestore(), ->rcu_read_unlock_special is
cleared one piece at a time.  Given that the "if" statements in this
function use the copy in "special", this commit removes the clearing
of the individual pieces in favor of clearing ->rcu_read_unlock_special
in one go just after it has been determined to be non-zero.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Currently, the .exp_hint flag is cleared in rcu_read_unlock_special(),
which works, but which can also prevent subsequent rcu_read_unlock() calls
from helping expedite the quiescent state needed by an ongoing expedited
RCU grace period.  This commit therefore defers clearing of .exp_hint
from rcu_read_unlock_special() to rcu_preempt_deferred_qs_irqrestore(),
thus ensuring that intervening calls to rcu_read_unlock() have a chance
to help end the expedited grace period.
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

CONFIG_PREEMPTION and CONFIG_PREEMPT_RCU are always identical,
but some code depends on CONFIG_PREEMPTION to access to
rcu_preempt functionality. This patch changes CONFIG_PREEMPTION
to CONFIG_PREEMPT_RCU in these cases.
Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com>
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Now that the kfree_rcu() special-casing has been removed from tree RCU,
this commit removes kfree_call_rcu_nobatch() since it is no longer needed.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit removes kfree_rcu() special-casing and the lazy-callback
handling from Tree RCU.  It moves some of this special casing to Tiny RCU,
the removal of which will be the subject of later commits.

This results in a nice negative delta.
Suggested-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
[ paulmck: Add slab.h #include, thanks to kbuild test robot <lkp@intel.com>. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit applies RCU's debug_objects debugging to the new batched
kfree_rcu() implementations.  The object is queued at the kfree_rcu()
call and dequeued during reclaim.

Tested that enabling CONFIG_DEBUG_OBJECTS_RCU_HEAD successfully detects
double kfree_rcu() calls.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
[ paulmck: Fix IRQ per kbuild test robot <lkp@intel.com> feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

During testing, it was observed that amount of memory consumed due
kfree_rcu() batching is 300-400MB. Previously we had only a single
head_free pointer pointing to the list of rcu_head(s) that are to be
freed after a grace period. Until this list is drained, we cannot queue
any more objects on it since such objects may not be ready to be
reclaimed when the worker thread eventually gets to drainin g the
head_free list.

We can do better by maintaining multiple lists as done by this patch.
Testing shows that memory consumption came down by around 100-150MB with
just adding another list. Adding more than 1 additional list did not
show any improvement.
Suggested-by: Paul E. McKenney <paulmck@linux.ibm.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
[ paulmck: Code style and initialization handling. ]
[ paulmck: Fix field name, reported by kbuild test robot <lkp@intel.com>. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Because the ->monitor_todo field is always protected by krcp->lock,
this commit downgrades from xchg() to non-atomic unmarked assignment
statements.
Signed-off-by: Joel Fernandes <joel@joelfernandes.org>
[ paulmck: Update to include early-boot kick code. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This test runs kfree_rcu() in a loop to measure performance of the new
kfree_rcu() batching functionality.

The following table shows results when booting with arguments:
rcuperf.kfree_loops=20000 rcuperf.kfree_alloc_num=8000
rcuperf.kfree_rcu_test=1 rcuperf.kfree_no_batch=X

rcuperf.kfree_no_batch=X    # Grace Periods	Test Duration (s)
  X=1 (old behavior)              9133                 11.5
  X=0 (new behavior)              1732                 12.5

On a 16 CPU system with the above boot parameters, we see that the total
number of grace periods that elapse during the test drops from 9133 when
not batching to 1732 when batching (a 5X improvement). The kfree_rcu()
flood itself slows down a bit when batching, though, as shown.

Note that the active memory consumption during the kfree_rcu() flood
does increase to around 200-250MB due to the batching (from around 50MB
without batching). However, this memory consumption is relatively
constant. In other words, the system is able to keep up with the
kfree_rcu() load. The memory consumption comes down considerably if
KFREE_DRAIN_JIFFIES is increased from HZ/50 to HZ/80. A later patch will
reduce memory consumption further by using multiple lists.

Also, when running the test, please disable CONFIG_DEBUG_PREEMPT and
CONFIG_PROVE_RCU for realistic comparisons with/without batching.
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Recently a discussion about stability and performance of a system
involving a high rate of kfree_rcu() calls surfaced on the list [1]
which led to another discussion how to prepare for this situation.

This patch adds basic batching support for kfree_rcu(). It is "basic"
because we do none of the slab management, dynamic allocation, code
moving or any of the other things, some of which previous attempts did
[2]. These fancier improvements can be follow-up patches and there are
different ideas being discussed in those regards. This is an effort to
start simple, and build up from there. In the future, an extension to
use kfree_bulk and possibly per-slab batching could be done to further
improve performance due to cache-locality and slab-specific bulk free
optimizations. By using an array of pointers, the worker thread
processing the work would need to read lesser data since it does not
need to deal with large rcu_head(s) any longer.

Torture tests follow in the next patch and show improvements of around
5x reduction in number of  grace periods on a 16 CPU system. More
details and test data are in that patch.

There is an implication with rcu_barrier() with this patch. Since the
kfree_rcu() calls can be batched, and may not be handed yet to the RCU
machinery in fact, the monitor may not have even run yet to do the
queue_rcu_work(), there seems no easy way of implementing rcu_barrier()
to wait for those kfree_rcu()s that are already made. So this means a
kfree_rcu() followed by an rcu_barrier() does not imply that memory will
be freed once rcu_barrier() returns.

Another implication is higher active memory usage (although not
run-away..) until the kfree_rcu() flooding ends, in comparison to
without batching. More details about this are in the second patch which
adds an rcuperf test.

Finally, in the near future we will get rid of kfree_rcu() special casing
within RCU such as in rcu_do_batch and switch everything to just
batching. Currently we don't do that since timer subsystem is not yet up
and we cannot schedule the kfree_rcu() monitor as the timer subsystem's
lock are not initialized. That would also mean getting rid of
kfree_call_rcu_nobatch() entirely.

[1] http://lore.kernel.org/lkml/20190723035725-mutt-send-email-mst@kernel.org
[2] https://lkml.org/lkml/2017/12/19/824

Cc: kernel-team@android.com
Cc: kernel-team@lge.com
Co-developed-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Byungchul Park <byungchul.park@lge.com>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
[ paulmck: Applied 0day and Paul Walmsley feedback on ->monitor_todo. ]
[ paulmck: Make it work during early boot. ]
[ paulmck: Add a crude early boot self-test. ]
[ paulmck: Style adjustments and experimental docbook structure header. ]
Link: https://lore.kernel.org/lkml/alpine.DEB.2.21.9999.1908161931110.32497@viisi.sifive.com/T/#me9956f66cb611b95d26ae92700e1d901f46e8c59Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This patch adds the macro list_tail_rcu() and documents it.
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>
[ paulmck: Reword a bit. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This patch changes the docbook comment "head for your list"
to "head of the list".
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This patch adds docbook comment headers for hlist_nulls_first_rcu()
and hlist_nulls_next_rcu() in rculist_nulls.h.
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit adds an hlist_nulls_unhashed_lockless() to allow lockless
checking for whether or note an hlist_nulls_node is hashed or not.
While in the area, this commit also adds a docbook comment to the existing
hlist_nulls_unhashed() function.
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

[ paulmck: Fix typo found by kbuild test robot. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Eric Dumazet supplied a KCSAN report of a bug that forces use
of hlist_unhashed_lockless() from sk_unhashed():

------------------------------------------------------------------------

BUG: KCSAN: data-race in inet_unhash / inet_unhash

write to 0xffff8880a69a0170 of 8 bytes by interrupt on cpu 1:
 __hlist_nulls_del include/linux/list_nulls.h:88 [inline]
 hlist_nulls_del_init_rcu include/linux/rculist_nulls.h:36 [inline]
 __sk_nulls_del_node_init_rcu include/net/sock.h:676 [inline]
 inet_unhash+0x38f/0x4a0 net/ipv4/inet_hashtables.c:612
 tcp_set_state+0xfa/0x3e0 net/ipv4/tcp.c:2249
 tcp_done+0x93/0x1e0 net/ipv4/tcp.c:3854
 tcp_write_err+0x7e/0xc0 net/ipv4/tcp_timer.c:56
 tcp_retransmit_timer+0x9b8/0x16d0 net/ipv4/tcp_timer.c:479
 tcp_write_timer_handler+0x42d/0x510 net/ipv4/tcp_timer.c:599
 tcp_write_timer+0xd1/0xf0 net/ipv4/tcp_timer.c:619
 call_timer_fn+0x5f/0x2f0 kernel/time/timer.c:1404
 expire_timers kernel/time/timer.c:1449 [inline]
 __run_timers kernel/time/timer.c:1773 [inline]
 __run_timers kernel/time/timer.c:1740 [inline]
 run_timer_softirq+0xc0c/0xcd0 kernel/time/timer.c:1786
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xbb/0xe0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0xe6/0x280 arch/x86/kernel/apic/apic.c:1137
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
 native_safe_halt+0xe/0x10 arch/x86/kernel/paravirt.c:71
 arch_cpu_idle+0x1f/0x30 arch/x86/kernel/process.c:571
 default_idle_call+0x1e/0x40 kernel/sched/idle.c:94
 cpuidle_idle_call kernel/sched/idle.c:154 [inline]
 do_idle+0x1af/0x280 kernel/sched/idle.c:263
 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:355
 start_secondary+0x208/0x260 arch/x86/kernel/smpboot.c:264
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241

read to 0xffff8880a69a0170 of 8 bytes by interrupt on cpu 0:
 sk_unhashed include/net/sock.h:607 [inline]
 inet_unhash+0x3d/0x4a0 net/ipv4/inet_hashtables.c:592
 tcp_set_state+0xfa/0x3e0 net/ipv4/tcp.c:2249
 tcp_done+0x93/0x1e0 net/ipv4/tcp.c:3854
 tcp_write_err+0x7e/0xc0 net/ipv4/tcp_timer.c:56
 tcp_retransmit_timer+0x9b8/0x16d0 net/ipv4/tcp_timer.c:479
 tcp_write_timer_handler+0x42d/0x510 net/ipv4/tcp_timer.c:599
 tcp_write_timer+0xd1/0xf0 net/ipv4/tcp_timer.c:619
 call_timer_fn+0x5f/0x2f0 kernel/time/timer.c:1404
 expire_timers kernel/time/timer.c:1449 [inline]
 __run_timers kernel/time/timer.c:1773 [inline]
 __run_timers kernel/time/timer.c:1740 [inline]
 run_timer_softirq+0xc0c/0xcd0 kernel/time/timer.c:1786
 __do_softirq+0x115/0x33f kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xbb/0xe0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:536 [inline]
 smp_apic_timer_interrupt+0xe6/0x280 arch/x86/kernel/apic/apic.c:1137
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:830
 native_safe_halt+0xe/0x10 arch/x86/kernel/paravirt.c:71
 arch_cpu_idle+0x1f/0x30 arch/x86/kernel/process.c:571
 default_idle_call+0x1e/0x40 kernel/sched/idle.c:94
 cpuidle_idle_call kernel/sched/idle.c:154 [inline]
 do_idle+0x1af/0x280 kernel/sched/idle.c:263
 cpu_startup_entry+0x1b/0x20 kernel/sched/idle.c:355
 rest_init+0xec/0xf6 init/main.c:452
 arch_call_rest_init+0x17/0x37
 start_kernel+0x838/0x85e init/main.c:786
 x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:490
 x86_64_start_kernel+0x72/0x76 arch/x86/kernel/head64.c:471
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:241

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine,
BIOS Google 01/01/2011

------------------------------------------------------------------------

This commit therefore replaces C-language assignments with WRITE_ONCE()
in include/linux/list_nulls.h and include/linux/rculist_nulls.h.

Reported-by: Eric Dumazet <edumazet@google.com> # For KCSAN
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Each of rcu_state, rcu_rnp_online_cpus(), rcu_dynticks_curr_cpu_in_eqs(),
and rcu_dynticks_snap() are used only in the kernel/rcu/tree.o translation
unit, and may thus be marked static.  This commit therefore makes this
change.
Reported-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>

Now that the calls to rcu_swap_protected() have been replaced by
rcu_replace_pointer(), this commit removes rcu_swap_protected().

Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Shane M Seymour <shane.seymour@hpe.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>

This commit replaces the use of rcu_swap_protected() with the more
intuitively appealing rcu_replace_pointer() as a step towards removing
rcu_swap_protected().

Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: "Martin K. Petersen" <martin.petersen@oracle.com>
[ paulmck: Apply Matthias Brugger feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: "Martin K. Petersen" <martin.petersen@oracle.com>
Acked-by: Kalle Valo <kvalo@codeaurora.org>
Cc: Felix Fietkau <nbd@nbd.name>
Cc: Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>
Cc: Ryder Lee <ryder.lee@mediatek.com>
Cc: Roy Luo <royluo@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: <linux-wireless@vger.kernel.org>
Cc: <netdev@vger.kernel.org>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: <linux-mediatek@lists.infradead.org>

This commit replaces the use of rcu_swap_protected() with the more
intuitively appealing rcu_replace_pointer() as a step towards removing
rcu_swap_protected().

Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
[ paulmck: Updated based on Ying Xue and Tuong Lien Tong feedback. ]
Cc: Jon Maloy <jon.maloy@ericsson.com>
Cc: Ying Xue <ying.xue@windriver.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: <netdev@vger.kernel.org>
Cc: <tipc-discussion@lists.sourceforge.net>

Reported-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This patch updates the list of RCU API in whatisRCU.rst.
Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>
Tested-by: Amol Grover <frextrite@gmail.com>
Tested-by: Phong Tran <tranmanphong@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

Convert rcubarrier.txt to rcubarrier.rst and add it to index.rst.

Format file according to reST
- Add headings and sub-headings
- Add code segments
- Add cross-references to quizes and answers
Signed-off-by: Amol Grover <frextrite@gmail.com>
Tested-by: Phong Tran <tranmanphong@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This patch converts rcu_dereference.txt to rcu_dereference.rst and
adds it to index.rst
Signed-off-by: Amol Grover <frextrite@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

This commit updates whatisRCU.txt to the new .rst format.
This change includes:

- Formatting bullet lists
- Adding literal blocks
- Links from table of contents to corresponding sections
- Links to external documents
- Reformat quick quizzes
Signed-off-by: Phong Tran <tranmanphong@gmail.com>
Tested-by: Madhuparna Bhowmik <madhuparnabhowmik04@gmail.com>
[ tranmanphong: Apply Amol Grover feedback. ]
Reviewed-by: Amol Grover <frextrite@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>