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Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

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Pull RCU updates from Ingo Molnar:
 "The changes in this cycle were:

   - Adding transitivity uniformly to rcu_node structure ->lock
     acquisitions.  (This is implemented by the first two commits on top
     of v4.4-rc2 due to the pervasive nature of this change.)

   - Documentation updates, including RCU requirements.

   - Expedited grace-period changes.

   - Miscellaneous fixes.

   - Linked-list fixes, courtesy of KTSAN.

   - Torture-test updates.

   - Late-breaking fix to sysrq-generated crash.

  One thing I should note is that these pieces of documentation are
  fairly large files:

    .../RCU/Design/Requirements/Requirements.html      | 2897 ++++++++++++++++++++
    .../RCU/Design/Requirements/Requirements.htmlx     | 2741 ++++++++++++++++++

  and are written in HTML, not the usual .txt style.  I hope they are
  fine"

Paul McKenney explains the html docs:
 "For whatever it is worth, the reason for this unconventional choice
  was that attempts to do the diagrams in ASCII art failed miserably.

  And attempts to do ASCII art for the upcoming documentation of the
  data structures failed even more miserably"

* 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (49 commits)
  sysrq: Fix warning in sysrq generated crash.
  list: Add lockless list traversal primitives
  rcu: Make rcu_gp_init() be bool rather than int
  rcu: Move wakeup out from under rnp->lock
  rcu: Fix comment for rcu_dereference_raw_notrace
  rcu: Don't redundantly disable irqs in rcu_irq_{enter,exit}()
  rcu: Make cpu_needs_another_gp() be bool
  rcu: Eliminate unused rcu_init_one() argument
  rcu: Remove TINY_RCU bloat from pointless boot parameters
  torture: Place console.log files correctly from the get-go
  torture: Abbreviate console error dump
  rcutorture: Print symbolic name for ->gp_state
  rcutorture: Print symbolic name for rcu_torture_writer_state
  rcutorture: Remove CONFIG_RCU_USER_QS from rcutorture selftest doc
  rcutorture: Default grace period to three minutes, allow override
  rcutorture:  Dump stack when GP kthread stalls
  rcutorture: Flag nonexistent RCU GP kthread
  rcutorture: Add batch number to script printout
  Documentation/memory-barriers.txt: Fix ACCESS_ONCE thinko
  documentation: Update RCU requirements based on expedited changes
  ...
This commit is contained in:
Linus Torvalds
2016-01-11 13:46:11 -08:00
parent ddf1d6238d 3104fb3dd4
commit 9061cbe62a
34 changed files with 7550 additions and 285 deletions
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id="tspan3017">Read-Mostly, Stale &amp;</tspan></text>
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style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
id="tspan3019">Inconsistent Data OK</tspan></text>
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id="tspan3021">(RCU Works Great!!!)</tspan></text>
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style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
id="tspan3023">(RCU Works Well)</tspan></text>
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id="tspan3025">Read-Mostly, Need Consistent Data</tspan></text>
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style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
id="tspan3027">Read-Write, Need Consistent Data</tspan></text>
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sodipodi:linespacing="125%">Update-Mostly, Need Consistent Data</text>
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id="text28"
sodipodi:linespacing="125%"
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;fill:#000000;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"><tspan
style="font-size:427.63009644px;font-style:normal;font-variant:normal;font-weight:normal;font-stretch:normal;text-align:center;line-height:125%;writing-mode:lr-tb;text-anchor:middle;font-family:Nimbus Sans L;-inkscape-font-specification:Nimbus Sans L"
id="tspan3029">(RCU Might Be OK...)</tspan></text>
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sodipodi:linespacing="125%">(1) Provide Existence Guarantees For Update-Friendly Mechanisms</text>
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sodipodi:linespacing="125%">(2) Provide Wait-Free Read-Side Primitives for Real-Time Use)</text>
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font-style="normal"
font-weight="normal"
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sodipodi:linespacing="125%">(RCU is Very Unlikely to be the Right Tool For The Job, But it Can:</text>
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108
Documentation/RCU/Design/htmlqqz.sh Executable file
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@@ -0,0 +1,108 @@
#!/bin/sh
#
# Usage: sh htmlqqz.sh file
#
# Extracts and converts quick quizzes in a proto-HTML document file.htmlx.
# Commands, all of which must be on a line by themselves:
#
# "<p>@@QQ@@": Start of a quick quiz.
# "<p>@@QQA@@": Start of a quick-quiz answer.
# "<p>@@QQE@@": End of a quick-quiz answer, and thus of the quick quiz.
# "<p>@@QQAL@@": Place to put quick-quiz answer list.
#
# Places the result in file.html.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, you can access it online at
# http://www.gnu.org/licenses/gpl-2.0.html.
#
# Copyright (c) 2013 Paul E. McKenney, IBM Corporation.
fn=$1
if test ! -r $fn.htmlx
then
echo "Error: $fn.htmlx unreadable."
exit 1
fi
echo "<!-- DO NOT HAND EDIT. -->" > $fn.html
echo "<!-- Instead, edit $fn.htmlx and run 'sh htmlqqz.sh $fn' -->" >> $fn.html
awk < $fn.htmlx >> $fn.html '
state == "" && $1 != "<p>@@QQ@@" && $1 != "<p>@@QQAL@@" {
print $0;
if ($0 ~ /^<p>@@QQ/)
print "Bad Quick Quiz command: " NR " (expected <p>@@QQ@@ or <p>@@QQAL@@)." > "/dev/stderr"
next;
}
state == "" && $1 == "<p>@@QQ@@" {
qqn++;
qqlineno = NR;
haveqq = 1;
state = "qq";
print "<p><a name=\"Quick Quiz " qqn "\"><b>Quick Quiz " qqn "</b>:</a>"
next;
}
state == "qq" && $1 != "<p>@@QQA@@" {
qq[qqn] = qq[qqn] $0 "\n";
print $0
if ($0 ~ /^<p>@@QQ/)
print "Bad Quick Quiz command: " NR ". (expected <p>@@QQA@@)" > "/dev/stderr"
next;
}
state == "qq" && $1 == "<p>@@QQA@@" {
state = "qqa";
print "<br><a href=\"#qq" qqn "answer\">Answer</a>"
next;
}
state == "qqa" && $1 != "<p>@@QQE@@" {
qqa[qqn] = qqa[qqn] $0 "\n";
if ($0 ~ /^<p>@@QQ/)
print "Bad Quick Quiz command: " NR " (expected <p>@@QQE@@)." > "/dev/stderr"
next;
}
state == "qqa" && $1 == "<p>@@QQE@@" {
state = "";
next;
}
state == "" && $1 == "<p>@@QQAL@@" {
haveqq = "";
print "<h3><a name=\"Answers to Quick Quizzes\">"
print "Answers to Quick Quizzes</a></h3>"
print "";
for (i = 1; i <= qqn; i++) {
print "<a name=\"qq" i "answer\"></a>"
print "<p><b>Quick Quiz " i "</b>:"
print qq[i];
print "";
print "</p><p><b>Answer</b>:"
print qqa[i];
print "";
print "</p><p><a href=\"#Quick%20Quiz%20" i "\"><b>Back to Quick Quiz " i "</b>.</a>"
print "";
}
next;
}
END {
if (state != "")
print "Unterminated Quick Quiz: " qqlineno "." > "/dev/stderr"
else if (haveqq)
print "Missing \"<p>@@QQAL@@\", no Quick Quiz." > "/dev/stderr"
}'

25
Documentation/kernel-parameters.txt
View File

@@ -3296,18 +3296,35 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
rcutorture.verbose= [KNL]
Enable additional printk() statements.
rcupdate.rcu_cpu_stall_suppress= [KNL]
Suppress RCU CPU stall warning messages.
rcupdate.rcu_cpu_stall_timeout= [KNL]
Set timeout for RCU CPU stall warning messages.
rcupdate.rcu_expedited= [KNL]
Use expedited grace-period primitives, for
example, synchronize_rcu_expedited() instead
of synchronize_rcu(). This reduces latency,
but can increase CPU utilization, degrade
real-time latency, and degrade energy efficiency.
No effect on CONFIG_TINY_RCU kernels.
rcupdate.rcu_cpu_stall_suppress= [KNL]
Suppress RCU CPU stall warning messages.
rcupdate.rcu_normal= [KNL]
Use only normal grace-period primitives,
for example, synchronize_rcu() instead of
synchronize_rcu_expedited(). This improves
real-time latency, CPU utilization, and
energy efficiency, but can expose users to
increased grace-period latency. This parameter
overrides rcupdate.rcu_expedited. No effect on
CONFIG_TINY_RCU kernels.
rcupdate.rcu_cpu_stall_timeout= [KNL]
Set timeout for RCU CPU stall warning messages.
rcupdate.rcu_normal_after_boot= [KNL]
Once boot has completed (that is, after
rcu_end_inkernel_boot() has been invoked), use
only normal grace-period primitives. No effect
on CONFIG_TINY_RCU kernels.
rcupdate.rcu_task_stall_timeout= [KNL]
Set timeout in jiffies for RCU task stall warning

8
Documentation/memory-barriers.txt
View File

@@ -194,7 +194,7 @@ There are some minimal guarantees that may be expected of a CPU:
(*) On any given CPU, dependent memory accesses will be issued in order, with
respect to itself. This means that for:
WRITE_ONCE(Q, P); smp_read_barrier_depends(); D = READ_ONCE(*Q);
Q = READ_ONCE(P); smp_read_barrier_depends(); D = READ_ONCE(*Q);
the CPU will issue the following memory operations:
@@ -202,9 +202,9 @@ There are some minimal guarantees that may be expected of a CPU:
and always in that order. On most systems, smp_read_barrier_depends()
does nothing, but it is required for DEC Alpha. The READ_ONCE()
and WRITE_ONCE() are required to prevent compiler mischief. Please
note that you should normally use something like rcu_dereference()
instead of open-coding smp_read_barrier_depends().
is required to prevent compiler mischief. Please note that you
should normally use something like rcu_dereference() instead of
open-coding smp_read_barrier_depends().
(*) Overlapping loads and stores within a particular CPU will appear to be
ordered within that CPU. This means that for:

6
drivers/tty/sysrq.c
View File

@@ -133,6 +133,12 @@ static void sysrq_handle_crash(int key)
{
char *killer = NULL;
/* we need to release the RCU read lock here,
* otherwise we get an annoying
* 'BUG: sleeping function called from invalid context'
* complaint from the kernel before the panic.
*/
rcu_read_unlock();
panic_on_oops = 1; /* force panic */
wmb();
*killer = 1;

14
include/linux/list.h
View File

@@ -24,7 +24,7 @@
static inline void INIT_LIST_HEAD(struct list_head *list)
{
list->next = list;
WRITE_ONCE(list->next, list);
list->prev = list;
}
@@ -42,7 +42,7 @@ static inline void __list_add(struct list_head *new,
next->prev = new;
new->next = next;
new->prev = prev;
prev->next = new;
WRITE_ONCE(prev->next, new);
}
#else
extern void __list_add(struct list_head *new,
@@ -186,7 +186,7 @@ static inline int list_is_last(const struct list_head *list,
*/
static inline int list_empty(const struct list_head *head)
{
return head->next == head;
return READ_ONCE(head->next) == head;
}
/**
@@ -608,7 +608,7 @@ static inline int hlist_unhashed(const struct hlist_node *h)
static inline int hlist_empty(const struct hlist_head *h)
{
return !h->first;
return !READ_ONCE(h->first);
}
static inline void __hlist_del(struct hlist_node *n)
@@ -642,7 +642,7 @@ static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
n->next = first;
if (first)
first->pprev = &n->next;
h->first = n;
WRITE_ONCE(h->first, n);
n->pprev = &h->first;
}
@@ -653,14 +653,14 @@ static inline void hlist_add_before(struct hlist_node *n,
n->pprev = next->pprev;
n->next = next;
next->pprev = &n->next;
*(n->pprev) = n;
WRITE_ONCE(*(n->pprev), n);
}
static inline void hlist_add_behind(struct hlist_node *n,
struct hlist_node *prev)
{
n->next = prev->next;
prev->next = n;
WRITE_ONCE(prev->next, n);
n->pprev = &prev->next;
if (n->next)

2
include/linux/list_bl.h
View File

@@ -70,7 +70,7 @@ static inline void hlist_bl_set_first(struct hlist_bl_head *h,
static inline int hlist_bl_empty(const struct hlist_bl_head *h)
{
return !((unsigned long)h->first & ~LIST_BL_LOCKMASK);
return !((unsigned long)READ_ONCE(h->first) & ~LIST_BL_LOCKMASK);
}
static inline void hlist_bl_add_head(struct hlist_bl_node *n,

2
include/linux/list_nulls.h
View File

@@ -57,7 +57,7 @@ static inline int hlist_nulls_unhashed(const struct hlist_nulls_node *h)
static inline int hlist_nulls_empty(const struct hlist_nulls_head *h)
{
return is_a_nulls(h->first);
return is_a_nulls(READ_ONCE(h->first));
}
static inline void hlist_nulls_add_head(struct hlist_nulls_node *n,

105
include/linux/rculist.h
View File

@@ -179,32 +179,31 @@ static inline void list_replace_rcu(struct list_head *old,
}
/**
* list_splice_init_rcu - splice an RCU-protected list into an existing list.
* __list_splice_init_rcu - join an RCU-protected list into an existing list.
* @list: the RCU-protected list to splice
* @head: the place in the list to splice the first list into
* @prev: points to the last element of the existing list
* @next: points to the first element of the existing list
* @sync: function to sync: synchronize_rcu(), synchronize_sched(), ...
*
* @head can be RCU-read traversed concurrently with this function.
* The list pointed to by @prev and @next can be RCU-read traversed
* concurrently with this function.
*
* Note that this function blocks.
*
* Important note: the caller must take whatever action is necessary to
* prevent any other updates to @head. In principle, it is possible
* to modify the list as soon as sync() begins execution.
* If this sort of thing becomes necessary, an alternative version
* based on call_rcu() could be created. But only if -really-
* needed -- there is no shortage of RCU API members.
* Important note: the caller must take whatever action is necessary to prevent
* any other updates to the existing list. In principle, it is possible to
* modify the list as soon as sync() begins execution. If this sort of thing
* becomes necessary, an alternative version based on call_rcu() could be
* created. But only if -really- needed -- there is no shortage of RCU API
* members.
*/
static inline void list_splice_init_rcu(struct list_head *list,
struct list_head *head,
void (*sync)(void))
static inline void __list_splice_init_rcu(struct list_head *list,
struct list_head *prev,
struct list_head *next,
void (*sync)(void))
{
struct list_head *first = list->next;
struct list_head *last = list->prev;
struct list_head *at = head->next;
if (list_empty(list))
return;
/*
* "first" and "last" tracking list, so initialize it. RCU readers
@@ -231,10 +230,40 @@ static inline void list_splice_init_rcu(struct list_head *list,
* this function.
*/
last->next = at;
rcu_assign_pointer(list_next_rcu(head), first);
first->prev = head;
at->prev = last;
last->next = next;
rcu_assign_pointer(list_next_rcu(prev), first);
first->prev = prev;
next->prev = last;
}
/**
* list_splice_init_rcu - splice an RCU-protected list into an existing list,
* designed for stacks.
* @list: the RCU-protected list to splice
* @head: the place in the existing list to splice the first list into
* @sync: function to sync: synchronize_rcu(), synchronize_sched(), ...
*/
static inline void list_splice_init_rcu(struct list_head *list,
struct list_head *head,
void (*sync)(void))
{
if (!list_empty(list))
__list_splice_init_rcu(list, head, head->next, sync);
}
/**
* list_splice_tail_init_rcu - splice an RCU-protected list into an existing
* list, designed for queues.
* @list: the RCU-protected list to splice
* @head: the place in the existing list to splice the first list into
* @sync: function to sync: synchronize_rcu(), synchronize_sched(), ...
*/
static inline void list_splice_tail_init_rcu(struct list_head *list,
struct list_head *head,
void (*sync)(void))
{
if (!list_empty(list))
__list_splice_init_rcu(list, head->prev, head, sync);
}
/**
@@ -304,6 +333,42 @@ static inline void list_splice_init_rcu(struct list_head *list,
&pos->member != (head); \
pos = list_entry_rcu(pos->member.next, typeof(*pos), member))
/**
* list_entry_lockless - get the struct for this entry
* @ptr: the &struct list_head pointer.
* @type: the type of the struct this is embedded in.
* @member: the name of the list_head within the struct.
*
* This primitive may safely run concurrently with the _rcu list-mutation
* primitives such as list_add_rcu(), but requires some implicit RCU
* read-side guarding. One example is running within a special
* exception-time environment where preemption is disabled and where
* lockdep cannot be invoked (in which case updaters must use RCU-sched,
* as in synchronize_sched(), call_rcu_sched(), and friends). Another
* example is when items are added to the list, but never deleted.
*/
#define list_entry_lockless(ptr, type, member) \
container_of((typeof(ptr))lockless_dereference(ptr), type, member)
/**
* list_for_each_entry_lockless - iterate over rcu list of given type
* @pos: the type * to use as a loop cursor.
* @head: the head for your list.
* @member: the name of the list_struct within the struct.
*
* This primitive may safely run concurrently with the _rcu list-mutation
* primitives such as list_add_rcu(), but requires some implicit RCU
* read-side guarding. One example is running within a special
* exception-time environment where preemption is disabled and where
* lockdep cannot be invoked (in which case updaters must use RCU-sched,
* as in synchronize_sched(), call_rcu_sched(), and friends). Another
* example is when items are added to the list, but never deleted.
*/
#define list_for_each_entry_lockless(pos, head, member) \
for (pos = list_entry_lockless((head)->next, typeof(*pos), member); \
&pos->member != (head); \
pos = list_entry_lockless(pos->member.next, typeof(*pos), member))
/**
* list_for_each_entry_continue_rcu - continue iteration over list of given type
* @pos: the type * to use as a loop cursor.

21
include/linux/rcupdate.h
View File

@@ -48,10 +48,17 @@
#include <asm/barrier.h>
#ifndef CONFIG_TINY_RCU
extern int rcu_expedited; /* for sysctl */
extern int rcu_normal; /* also for sysctl */
#endif /* #ifndef CONFIG_TINY_RCU */
#ifdef CONFIG_TINY_RCU
/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
static inline bool rcu_gp_is_normal(void) /* Internal RCU use. */
{
return true;
}
static inline bool rcu_gp_is_expedited(void) /* Internal RCU use. */
{
return false;
@@ -65,6 +72,7 @@ static inline void rcu_unexpedite_gp(void)
{
}
#else /* #ifdef CONFIG_TINY_RCU */
bool rcu_gp_is_normal(void); /* Internal RCU use. */
bool rcu_gp_is_expedited(void); /* Internal RCU use. */
void rcu_expedite_gp(void);
void rcu_unexpedite_gp(void);
@@ -321,7 +329,6 @@ static inline int rcu_preempt_depth(void)
/* Internal to kernel */
void rcu_init(void);
void rcu_end_inkernel_boot(void);
void rcu_sched_qs(void);
void rcu_bh_qs(void);
void rcu_check_callbacks(int user);
@@ -329,6 +336,12 @@ struct notifier_block;
int rcu_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu);
#ifndef CONFIG_TINY_RCU
void rcu_end_inkernel_boot(void);
#else /* #ifndef CONFIG_TINY_RCU */
static inline void rcu_end_inkernel_boot(void) { }
#endif /* #ifndef CONFIG_TINY_RCU */
#ifdef CONFIG_RCU_STALL_COMMON
void rcu_sysrq_start(void);
void rcu_sysrq_end(void);
@@ -379,9 +392,9 @@ static inline void rcu_init_nohz(void)
*/
#define RCU_NONIDLE(a) \
do { \
rcu_irq_enter(); \
rcu_irq_enter_irqson(); \
do { a; } while (0); \
rcu_irq_exit(); \
rcu_irq_exit_irqson(); \
} while (0)
/*
@@ -741,7 +754,7 @@ static inline void rcu_preempt_sleep_check(void)
* The tracing infrastructure traces RCU (we want that), but unfortunately
* some of the RCU checks causes tracing to lock up the system.
*
* The tracing version of rcu_dereference_raw() must not call
* The no-tracing version of rcu_dereference_raw() must not call
* rcu_read_lock_held().
*/
#define rcu_dereference_raw_notrace(p) __rcu_dereference_check((p), 1, __rcu)

8
include/linux/rcutiny.h
View File

@@ -181,6 +181,14 @@ static inline void rcu_irq_enter(void)
{
}
static inline void rcu_irq_exit_irqson(void)
{
}
static inline void rcu_irq_enter_irqson(void)
{
}
static inline void rcu_irq_exit(void)
{
}

4
include/linux/rcutree.h
View File

@@ -37,7 +37,7 @@ void rcu_cpu_stall_reset(void);
/*
* Note a virtualization-based context switch. This is simply a
* wrapper around rcu_note_context_switch(), which allows TINY_RCU
* to save a few bytes.
* to save a few bytes. The caller must have disabled interrupts.
*/
static inline void rcu_virt_note_context_switch(int cpu)
{
@@ -97,6 +97,8 @@ void rcu_idle_enter(void);
void rcu_idle_exit(void);
void rcu_irq_enter(void);
void rcu_irq_exit(void);
void rcu_irq_enter_irqson(void);
void rcu_irq_exit_irqson(void);
void exit_rcu(void);

4
include/linux/tracepoint.h
View File

@@ -171,8 +171,8 @@ extern void syscall_unregfunc(void);
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), \
rcu_irq_enter(), \
rcu_irq_exit()); \
rcu_irq_enter_irqson(), \
rcu_irq_exit_irqson()); \
}
#else
#define __DECLARE_TRACE_RCU(name, proto, args, cond, data_proto, data_args)

2
init/main.c
View File

@@ -943,6 +943,8 @@ static int __ref kernel_init(void *unused)
flush_delayed_fput();
rcu_end_inkernel_boot();
if (ramdisk_execute_command) {
ret = run_init_process(ramdisk_execute_command);
if (!ret)

26
kernel/ksysfs.c
View File

@@ -20,7 +20,7 @@
#include <linux/capability.h>
#include <linux/compiler.h>
#include <linux/rcupdate.h> /* rcu_expedited */
#include <linux/rcupdate.h> /* rcu_expedited and rcu_normal */
#define KERNEL_ATTR_RO(_name) \
static struct kobj_attribute _name##_attr = __ATTR_RO(_name)
@@ -144,11 +144,12 @@ static ssize_t fscaps_show(struct kobject *kobj,
}
KERNEL_ATTR_RO(fscaps);
#ifndef CONFIG_TINY_RCU
int rcu_expedited;
static ssize_t rcu_expedited_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sprintf(buf, "%d\n", rcu_expedited);
return sprintf(buf, "%d\n", READ_ONCE(rcu_expedited));
}
static ssize_t rcu_expedited_store(struct kobject *kobj,
struct kobj_attribute *attr,
@@ -161,6 +162,24 @@ static ssize_t rcu_expedited_store(struct kobject *kobj,
}
KERNEL_ATTR_RW(rcu_expedited);
int rcu_normal;
static ssize_t rcu_normal_show(struct kobject *kobj,
struct kobj_attribute *attr, char *buf)
{
return sprintf(buf, "%d\n", READ_ONCE(rcu_normal));
}
static ssize_t rcu_normal_store(struct kobject *kobj,
struct kobj_attribute *attr,
const char *buf, size_t count)
{
if (kstrtoint(buf, 0, &rcu_normal))
return -EINVAL;
return count;
}
KERNEL_ATTR_RW(rcu_normal);
#endif /* #ifndef CONFIG_TINY_RCU */
/*
* Make /sys/kernel/notes give the raw contents of our kernel .notes section.
*/
@@ -202,7 +221,10 @@ static struct attribute * kernel_attrs[] = {
&kexec_crash_size_attr.attr,
&vmcoreinfo_attr.attr,
#endif
#ifndef CONFIG_TINY_RCU
&rcu_expedited_attr.attr,
&rcu_normal_attr.attr,
#endif
NULL
};

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