rculist: add list_bidir_{del,prev}_rcu()

Currently there is no primitive for retrieving the previous list member.
To do this we need a new deletion primitive that doesn't poison the prev
pointer and

rculist: add list_bidir_{del,prev}_rcu()

Currently there is no primitive for retrieving the previous list member.
To do this we need a new deletion primitive that doesn't poison the prev
pointer and a corresponding retrieval helper. Note that it is not valid
to ues both list_del_rcu() and list_bidir_del_rcu() on the same list.

Link: https://lore.kernel.org/r/[email protected]
Reviewed-by: Paul E. McKenney <[email protected]>
Reviewed-by: Jeff Layton <[email protected]>
Suggested-by: Paul E. McKenney <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

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rcu: Better define "atomic" for list replacement

The kernel-doc headers for list_replace_rcu() and hlist_replace_rcu()
claim that the replacement is atomic, which it is, but only for readers.
Avoid

rcu: Better define "atomic" for list replacement

The kernel-doc headers for list_replace_rcu() and hlist_replace_rcu()
claim that the replacement is atomic, which it is, but only for readers.
Avoid confusion by making it clear that the atomic nature of these
functions applies only to readers, not to concurrent updaters.

Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Neeraj Upadhyay <[email protected]>

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rculist.h: docs: Fix wrong function summary

The brief summary in the docstring for function list_next_or_null_rcu()
states that the function is supposed to provide the "first" member of a
list, wher

rculist.h: docs: Fix wrong function summary

The brief summary in the docstring for function list_next_or_null_rcu()
states that the function is supposed to provide the "first" member of a
list, whereas in truth it returns the next member.

Change the docstring so it describes what the function actually does.

Signed-off-by: Philipp Stanner <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Neeraj Upadhyay (AMD) <[email protected]>

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rculist: Unify documentation about missing list_empty_rcu()

We have two separate sections that talk about why list_empty_rcu()
is not needed, so this commit consolidates them.

Signed-off-by: Julian

rculist: Unify documentation about missing list_empty_rcu()

We have two separate sections that talk about why list_empty_rcu()
is not needed, so this commit consolidates them.

Signed-off-by: Julian Wiedmann <[email protected]>
[ paulmck: The usual wordsmithing. ]
Signed-off-by: Paul E. McKenney <[email protected]>

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rculist: Introduce list/hlist_for_each_entry_srcu() macros

list/hlist_for_each_entry_rcu() provides an optional cond argument
to specify the lock held in the updater side.
However for SRCU read side

rculist: Introduce list/hlist_for_each_entry_srcu() macros

list/hlist_for_each_entry_rcu() provides an optional cond argument
to specify the lock held in the updater side.
However for SRCU read side, not providing the cond argument results
into false positive as whether srcu_read_lock is held or not is not
checked implicitly. Therefore, on read side the lockdep expression
srcu_read_lock_held(srcu struct) can solve this issue.

However, the function still fails to check the cases where srcu
protected list is traversed with rcu_read_lock() instead of
srcu_read_lock(). Therefore, to remove the false negative,
this patch introduces two new list traversal primitives :
list_for_each_entry_srcu() and hlist_for_each_entry_srcu().

Both of the functions have non-optional cond argument
as it is required for both read and update side, and simply checks
if the cond is true. For regular read side the lockdep expression
srcu_read_lock_head() can be passed as the cond argument to
list/hlist_for_each_entry_srcu().

Suggested-by: Paolo Bonzini <[email protected]>
Tested-by: Suraj Upadhyay <[email protected]>
Tested-by: Naresh Kamboju <[email protected]>
[ paulmck: Add "true" per kbuild test robot feedback. ]
Signed-off-by: Madhuparna Bhowmik <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

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rculist: Add ASSERT_EXCLUSIVE_ACCESS() to __list_splice_init_rcu()

After the sync() in __list_splice_init_rcu(), there should be no
readers traversing the old list. This commit therefore enlists th

rculist: Add ASSERT_EXCLUSIVE_ACCESS() to __list_splice_init_rcu()

After the sync() in __list_splice_init_rcu(), there should be no
readers traversing the old list. This commit therefore enlists the
help of KCSAN to verify this condition via a pair of calls to
ASSERT_EXCLUSIVE_ACCESS().

Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Marco Elver <[email protected]>

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rcu: Fix some kernel-doc warnings

The current code provokes some kernel-doc warnings:

./kernel/rcu/tree.c:2915: warning: Function parameter or member 'count' not described in 'kfree_rcu_cpu'
./in

rcu: Fix some kernel-doc warnings

The current code provokes some kernel-doc warnings:

./kernel/rcu/tree.c:2915: warning: Function parameter or member 'count' not described in 'kfree_rcu_cpu'
./include/linux/rculist.h:517: warning: bad line: [@right ][node2 ... ]
./include/linux/rculist.h:2: WARNING: Unexpected indentation.

This commit therefore moves the comment for "count" to the kernel-doc
markup and adds a missing "*" on one kernel-doc continuation line.

Signed-off-by: Mauro Carvalho Chehab <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

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rculist: Add hlists_swap_heads_rcu

Using the struct pid to refer to two tasks in de_thread was a clever
idea and ultimately too clever, as it has lead to proc_flush_task
being called inconsistently.

rculist: Add hlists_swap_heads_rcu

Using the struct pid to refer to two tasks in de_thread was a clever
idea and ultimately too clever, as it has lead to proc_flush_task
being called inconsistently.

To support rectifying this add hlists_swap_heads_rcu. An hlist
primitive that just swaps the hlist heads of two lists. This is
exactly what is needed for exchanging the pids of two tasks.

Only consideration of correctness of the code has been given,
as the caller is expected to be a slowpath.

Link: https://lore.kernel.org/lkml/[email protected]/
Acked-by: Linus Torvalds <[email protected]>
Acked-by: Oleg Nesterov <[email protected]>
Signed-off-by: "Eric W. Biederman" <[email protected]>

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Revert "rculist: Describe variadic macro argument in a Sphinx-compatible way"

This reverts commit f452ee096d95482892b101bde4fd037fa025d3cc.

The workaround became unnecessary with commit 43756e347f2

Revert "rculist: Describe variadic macro argument in a Sphinx-compatible way"

This reverts commit f452ee096d95482892b101bde4fd037fa025d3cc.

The workaround became unnecessary with commit 43756e347f21
("scripts/kernel-doc: Add support for named variable macro arguments").

Signed-off-by: Jonathan Neuschäfer <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

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rculist: Add brackets around cond argument in __list_check_rcu macro

Passing a complex lockdep condition to __list_check_rcu results
in false positive lockdep splat due to incorrect expression
evalu

rculist: Add brackets around cond argument in __list_check_rcu macro

Passing a complex lockdep condition to __list_check_rcu results
in false positive lockdep splat due to incorrect expression
evaluation.

For example, a lockdep check condition `cond1 || cond2` is
evaluated as `!cond1 || cond2 && !rcu_read_lock_any_held()`
which, according to operator precedence, evaluates to
`!cond1 || (cond2 && !rcu_read_lock_any_held())`.
This would result in a lockdep splat when cond1 is false
and cond2 is true which is logically incorrect.

Signed-off-by: Amol Grover <[email protected]>
Acked-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

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rculist.h: Add list_tail_rcu()

This patch adds the macro list_tail_rcu() and documents it.

Signed-off-by: Madhuparna Bhowmik <[email protected]>
[ paulmck: Reword a bit. ]
Signed-off-by

rculist.h: Add list_tail_rcu()

This patch adds the macro list_tail_rcu() and documents it.

Signed-off-by: Madhuparna Bhowmik <[email protected]>
[ paulmck: Reword a bit. ]
Signed-off-by: Paul E. McKenney <[email protected]>

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list: Add hlist_unhashed_lockless()

We would like to use hlist_unhashed() from timer_pending(),
which runs without protection of a lock.

Note that other callers might also want to use this variant.

list: Add hlist_unhashed_lockless()

We would like to use hlist_unhashed() from timer_pending(),
which runs without protection of a lock.

Note that other callers might also want to use this variant.

Instead of forcing a READ_ONCE() for all hlist_unhashed()
callers, add a new helper with an explicit _lockless suffix
in the name to better document what is going on.

Also add various WRITE_ONCE() in __hlist_del(), hlist_add_head()
and hlist_add_before()/hlist_add_behind() to pair with
the READ_ONCE().

Signed-off-by: Eric Dumazet <[email protected]>
Cc: Thomas Gleixner <[email protected]>
[ paulmck: Also add WRITE_ONCE() to rculist.h. ]
Signed-off-by: Paul E. McKenney <[email protected]>

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rculist: Describe variadic macro argument in a Sphinx-compatible way

Without this patch, Sphinx shows "variable arguments" as the description
of the cond argument, rather than the intended descripti

rculist: Describe variadic macro argument in a Sphinx-compatible way

Without this patch, Sphinx shows "variable arguments" as the description
of the cond argument, rather than the intended description, and prints
the following warnings:

./include/linux/rculist.h:374: warning: Excess function parameter 'cond' description in 'list_for_each_entry_rcu'
./include/linux/rculist.h:651: warning: Excess function parameter 'cond' description in 'hlist_for_each_entry_rcu'

Signed-off-by: Jonathan Neuschäfer <[email protected]>
Acked-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

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rcu: Add support for consolidated-RCU reader checking

This commit adds RCU-reader checks to list_for_each_entry_rcu() and
hlist_for_each_entry_rcu(). These checks are optional, and are indicated
by

rcu: Add support for consolidated-RCU reader checking

This commit adds RCU-reader checks to list_for_each_entry_rcu() and
hlist_for_each_entry_rcu(). These checks are optional, and are indicated
by a lockdep expression passed to a new optional argument to these two
macros. If this optional lockdep expression is omitted, these two macros
act as before, checking for an RCU read-side critical section.

Signed-off-by: Joel Fernandes (Google) <[email protected]>
[ paulmck: Update to eliminate return within macro and update comment. ]
Signed-off-by: Paul E. McKenney <[email protected]>

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treewide: Rename rcu_dereference_raw_notrace() to _check()

The rcu_dereference_raw_notrace() API name is confusing. It is equivalent
to rcu_dereference_raw() except that it also does sparse pointer

treewide: Rename rcu_dereference_raw_notrace() to _check()

The rcu_dereference_raw_notrace() API name is confusing. It is equivalent
to rcu_dereference_raw() except that it also does sparse pointer checking.

There are only a few users of rcu_dereference_raw_notrace(). This patches
renames all of them to be rcu_dereference_raw_check() with the "_check()"
indicating sparse checking.

Signed-off-by: Joel Fernandes (Google) <[email protected]>
[ paulmck: Fix checkpatch warnings about parentheses. ]
Signed-off-by: Paul E. McKenney <[email protected]>

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rcu: Clean up flavor-related definitions and comments in rculist.h

Signed-off-by: Paul E. McKenney <[email protected]>

rculist: Improve documentation for list_for_each_entry_from_rcu()

Unfortunately the patch for adding list_for_each_entry_from_rcu()
wasn't the final patch after all review. It is functionally
corre

rculist: Improve documentation for list_for_each_entry_from_rcu()

Unfortunately the patch for adding list_for_each_entry_from_rcu()
wasn't the final patch after all review. It is functionally
correct but the documentation was incomplete.

This patch adds this missing documentation which includes an update to
the documentation for list_for_each_entry_continue_rcu() to match the
documentation for the new list_for_each_entry_from_rcu(), and adds
list_for_each_entry_from_rcu() and the already existing
hlist_for_each_entry_from_rcu() to section 7 of whatisRCU.txt.

Reviewed-by: Paul E. McKenney <[email protected]>
Signed-off-by: NeilBrown <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

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rculist: add list_for_each_entry_from_rcu()

list_for_each_entry_from_rcu() is an RCU version of
list_for_each_entry_from(). It walks a linked list under rcu
protection, from a given start point.

I

rculist: add list_for_each_entry_from_rcu()

list_for_each_entry_from_rcu() is an RCU version of
list_for_each_entry_from(). It walks a linked list under rcu
protection, from a given start point.

It is similar to list_for_each_entry_continue_rcu() but starts *at*
the given position rather than *after* it.

Naturally, the start point must be known to be in the list.

Signed-off-by: NeilBrown <[email protected]>
Signed-off-by: Trond Myklebust <[email protected]>

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locking/barriers: Convert users of lockless_dereference() to READ_ONCE()

[ Note, this is a Git cherry-pick of the following commit:

506458efaf15 ("locking/barriers: Convert users of lockless_de

locking/barriers: Convert users of lockless_dereference() to READ_ONCE()

[ Note, this is a Git cherry-pick of the following commit:

506458efaf15 ("locking/barriers: Convert users of lockless_dereference() to READ_ONCE()")

... for easier x86 PTI code testing and back-porting. ]

READ_ONCE() now has an implicit smp_read_barrier_depends() call, so it
can be used instead of lockless_dereference() without any change in
semantics.

Signed-off-by: Will Deacon <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

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License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

Many source files in the tree are missing licensing information, which
makes it harder for compliance tools to determine the correct license.

By default all files without license information are under the default
license of the kernel, which is GPL version 2.

Update the files which contain no license information with the 'GPL-2.0'
SPDX license identifier. The SPDX identifier is a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.

How this work was done:

Patches were generated and checked against linux-4.14-rc6 for a subset of
the use cases:
- file had no licensing information it it.
- file was a */uapi/* one with no licensing information in it,
- file was a */uapi/* one with existing licensing information,

Further patches will be generated in subsequent months to fix up cases
where non-standard license headers were used, and references to license
had to be inferred by heuristics based on keywords.

The analysis to determine which SPDX License Identifier to be applied to
a file was done in a spreadsheet of side by side results from of the
output of two independent scanners (ScanCode & Windriver) producing SPDX
tag:value files created by Philippe Ombredanne. Philippe prepared the
base worksheet, and did an initial spot review of a few 1000 files.

The 4.13 kernel was the starting point of the analysis with 60,537 files
assessed. Kate Stewart did a file by file comparison of the scanner
results in the spreadsheet to determine which SPDX license identifier(s)
to be applied to the file. She confirmed any determination that was not
immediately clear with lawyers working with the Linux Foundation.

Criteria used to select files for SPDX license identifier tagging was:
- Files considered eligible had to be source code files.
- Make and config files were included as candidates if they contained >5
lines of source
- File already had some variant of a license header in it (even if <5
lines).

All documentation files were explicitly excluded.

The following heuristics were used to determine which SPDX license
identifiers to apply.

- when both scanners couldn't find any license traces, file was
considered to have no license information in it, and the top level
COPYING file license applied.

For non */uapi/* files that summary was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 11139

and resulted in the first patch in this series.

If that file was a */uapi/* path one, it was "GPL-2.0 WITH
Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was:

SPDX license identifier # files
---------------------------------------------------|-------
GPL-2.0 WITH Linux-syscall-note 930

and resulted in the second patch in this series.

- if a file had some form of licensing information in it, and was one
of the */uapi/* ones, it was denoted with the Linux-syscall-note if
any GPL family license was found in the file or had no licensing in
it (per prior point). Results summary:

SPDX license identifier # files
---------------------------------------------------|------
GPL-2.0 WITH Linux-syscall-note 270
GPL-2.0+ WITH Linux-syscall-note 169
((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21
((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17
LGPL-2.1+ WITH Linux-syscall-note 15
GPL-1.0+ WITH Linux-syscall-note 14
((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5
LGPL-2.0+ WITH Linux-syscall-note 4
LGPL-2.1 WITH Linux-syscall-note 3
((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3
((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1

and that resulted in the third patch in this series.

- when the two scanners agreed on the detected license(s), that became
the concluded license(s).

- when there was disagreement between the two scanners (one detected a
license but the other didn't, or they both detected different
licenses) a manual inspection of the file occurred.

- In most cases a manual inspection of the information in the file
resulted in a clear resolution of the license that should apply (and
which scanner probably needed to revisit its heuristics).

- When it was not immediately clear, the license identifier was
confirmed with lawyers working with the Linux Foundation.

- If there was any question as to the appropriate license identifier,
the file was flagged for further research and to be revisited later
in time.

In total, over 70 hours of logged manual review was done on the
spreadsheet to determine the SPDX license identifiers to apply to the
source files by Kate, Philippe, Thomas and, in some cases, confirmation
by lawyers working with the Linux Foundation.

Kate also obtained a third independent scan of the 4.13 code base from
FOSSology, and compared selected files where the other two scanners
disagreed against that SPDX file, to see if there was new insights. The
Windriver scanner is based on an older version of FOSSology in part, so
they are related.

Thomas did random spot checks in about 500 files from the spreadsheets
for the uapi headers and agreed with SPDX license identifier in the
files he inspected. For the non-uapi files Thomas did random spot checks
in about 15000 files.

In initial set of patches against 4.14-rc6, 3 files were found to have
copy/paste license identifier errors, and have been fixed to reflect the
correct identifier.

Additionally Philippe spent 10 hours this week doing a detailed manual
inspection and review of the 12,461 patched files from the initial patch
version early this week with:
- a full scancode scan run, collecting the matched texts, detected
license ids and scores
- reviewing anything where there was a license detected (about 500+
files) to ensure that the applied SPDX license was correct
- reviewing anything where there was no detection but the patch license
was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied
SPDX license was correct

This produced a worksheet with 20 files needing minor correction. This
worksheet was then exported into 3 different .csv files for the
different types of files to be modified.

These .csv files were then reviewed by Greg. Thomas wrote a script to
parse the csv files and add the proper SPDX tag to the file, in the
format that the file expected. This script was further refined by Greg
based on the output to detect more types of files automatically and to
distinguish between header and source .c files (which need different
comment types.) Finally Greg ran the script using the .csv files to
generate the patches.

Reviewed-by: Kate Stewart <[email protected]>
Reviewed-by: Philippe Ombredanne <[email protected]>
Reviewed-by: Thomas Gleixner <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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locking/barriers: Convert users of lockless_dereference() to READ_ONCE()

READ_ONCE() now has an implicit smp_read_barrier_depends() call, so it
can be used instead of lockless_dereference() without

locking/barriers: Convert users of lockless_dereference() to READ_ONCE()

READ_ONCE() now has an implicit smp_read_barrier_depends() call, so it
can be used instead of lockless_dereference() without any change in
semantics.

Signed-off-by: Will Deacon <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

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doc: Fix various RCU docbook comment-header problems

Because many of RCU's files have not been included into docbook, a
number of errors have accumulated. This commit fixes them.

Signed-off-by: Pa

doc: Fix various RCU docbook comment-header problems

Because many of RCU's files have not been included into docbook, a
number of errors have accumulated. This commit fixes them.

Signed-off-by: Paul E. McKenney <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

show more ...

hlist_add_tail_rcu disable sparse warning

sparse is unhappy about this code in hlist_add_tail_rcu:

struct hlist_node *i, *last = NULL;

for (i = hlist_first_rcu(h); i; i = hlist_nex

hlist_add_tail_rcu disable sparse warning

sparse is unhappy about this code in hlist_add_tail_rcu:

struct hlist_node *i, *last = NULL;

for (i = hlist_first_rcu(h); i; i = hlist_next_rcu(i))
last = i;

This is because hlist_next_rcu and hlist_next_rcu return
__rcu pointers.

It's a false positive - it's a write side primitive and so
does not need to be called in a read side critical section.

The following trivial patch disables the warning
without changing the behaviour in any way.

Note: __hlist_for_each_rcu would also remove the warning but it would be
confusing since it calls rcu_derefence and is designed to run in the rcu
read side critical section.

Signed-off-by: Michael S. Tsirkin <[email protected]>
Reviewed-by: Steven Rostedt (VMware) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

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rculist: Consolidate DEBUG_LIST for list_add_rcu()

This commit consolidates the debug checking for list_add_rcu() into the
new single __list_add_valid() debug function. Notably, this commit fixes
t

rculist: Consolidate DEBUG_LIST for list_add_rcu()

This commit consolidates the debug checking for list_add_rcu() into the
new single __list_add_valid() debug function. Notably, this commit fixes
the sanity check that was added in commit 17a801f4bfeb ("list_debug:
WARN for adding something already in the list"), which wasn't checking
RCU-protected lists.

Signed-off-by: Kees Cook <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Acked-by: Rik van Riel <[email protected]>

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rcu: Add list_next_or_null_rcu

This is a convenience function that returns the next entry in an RCU
list or NULL if at the end of the list.

Signed-off-by: Tom Herbert <[email protected]>
Signed-o

rcu: Add list_next_or_null_rcu

This is a convenience function that returns the next entry in an RCU
list or NULL if at the end of the list.

Signed-off-by: Tom Herbert <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

show more ...