A-Team_Digital_Solutions/android_kernel_motorola_sm6375
Watch
2
0
Fork
You've already forked android_kernel_motorola_sm6375
 0
mirror of https://github.com/BobTheBlinker/android_kernel_motorola_sm6375.git synced 2026-10-24 21:54:34 -04:00
Code Issues Projects Releases Packages Wiki Activity

Minor merge needed, due to function move.

Browse source 
Main excitement here is Peter Zijlstra's lockless rbtree optimization to
 speed module address lookup.  He found some abusers of the module lock
 doing that too.
 
 A little bit of parameter work here too; including Dan Streetman's breaking
 up the big param mutex so writing a parameter can load another module (yeah,
 really).  Unfortunately that broke the usual suspects, !CONFIG_MODULES and
 !CONFIG_SYSFS, so those fixes were appended too.
 
 Cheers,
 Rusty.
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1
 
 iQIcBAABAgAGBQJVkgKHAAoJENkgDmzRrbjxQpwQAJVmBN6jF3SnwbQXv9vRixjH
 58V33sb1G1RW+kXxQ3/e8jLX/4VaN479CufruXQp+IJWXsN/CH0lbC3k8m7u50d7
 b1Zeqd/Yrh79rkc11b0X1698uGCSMlzz+V54Z0QOTEEX+nSu2ZZvccFS4UaHkn3z
 rqDo00lb7rxQz8U25qro2OZrG6D3ub2q20TkWUB8EO4AOHkPn8KWP2r429Axrr0K
 wlDWDTTt8/IsvPbuPf3T15RAhq1avkMXWn9nDXDjyWbpLfTn8NFnWmtesgY7Jl4t
 GjbXC5WYekX3w2ZDB9KaT/DAMQ1a7RbMXNSz4RX4VbzDl+yYeSLmIh2G9fZb1PbB
 PsIxrOgy4BquOWsJPm+zeFPSC3q9Cfu219L4AmxSjiZxC3dlosg5rIB892Mjoyv4
 qxmg6oiqtc4Jxv+Gl9lRFVOqyHZrTC5IJ+xgfv1EyP6kKMUKLlDZtxZAuQxpUyxR
 HZLq220RYnYSvkWauikq4M8fqFM8bdt6hLJnv7bVqllseROk9stCvjSiE3A9szH5
 OgtOfYV5GhOeb8pCZqJKlGDw+RoJ21jtNCgOr6DgkNKV9CX/kL/Puwv8gnA0B0eh
 dxCeB7f/gcLl7Cg3Z3gVVcGlgak6JWrLf5ITAJhBZ8Lv+AtL2DKmwEWS/iIMRmek
 tLdh/a9GiCitqS0bT7GE
 =tWPQ
 -----END PGP SIGNATURE-----

Merge tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux

Pull module updates from Rusty Russell:
 "Main excitement here is Peter Zijlstra's lockless rbtree optimization
  to speed module address lookup.  He found some abusers of the module
  lock doing that too.

  A little bit of parameter work here too; including Dan Streetman's
  breaking up the big param mutex so writing a parameter can load
  another module (yeah, really).  Unfortunately that broke the usual
  suspects, !CONFIG_MODULES and !CONFIG_SYSFS, so those fixes were
  appended too"

* tag 'modules-next-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux: (26 commits)
  modules: only use mod->param_lock if CONFIG_MODULES
  param: fix module param locks when !CONFIG_SYSFS.
  rcu: merge fix for Convert ACCESS_ONCE() to READ_ONCE() and WRITE_ONCE()
  module: add per-module param_lock
  module: make perm const
  params: suppress unused variable error, warn once just in case code changes.
  modules: clarify CONFIG_MODULE_COMPRESS help, suggest 'N'.
  kernel/module.c: avoid ifdefs for sig_enforce declaration
  kernel/workqueue.c: remove ifdefs over wq_power_efficient
  kernel/params.c: export param_ops_bool_enable_only
  kernel/params.c: generalize bool_enable_only
  kernel/module.c: use generic module param operaters for sig_enforce
  kernel/params: constify struct kernel_param_ops uses
  sysfs: tightened sysfs permission checks
  module: Rework module_addr_{min,max}
  module: Use __module_address() for module_address_lookup()
  module: Make the mod_tree stuff conditional on PERF_EVENTS || TRACING
  module: Optimize __module_address() using a latched RB-tree
  rbtree: Implement generic latch_tree
  seqlock: Introduce raw_read_seqcount_latch()
  ...
This commit is contained in:
Linus Torvalds 2015-07-01 10:49:25 -07:00
commit 02201e3f1b
48 changed files with 883 additions and 355 deletions
Download patch file Download diff file Expand all files Collapse all files

15
include/linux/compiler.h
View file

@ -475,6 +475,21 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
(volatile typeof(x) *)&(x); })
#define ACCESS_ONCE(x) (*__ACCESS_ONCE(x))
/**
* lockless_dereference() - safely load a pointer for later dereference
* @p: The pointer to load
*
* Similar to rcu_dereference(), but for situations where the pointed-to
* object's lifetime is managed by something other than RCU. That
* "something other" might be reference counting or simple immortality.
*/
#define lockless_dereference(p) \
({ \
typeof(p) _________p1 = READ_ONCE(p); \
smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
(_________p1); \
})
/* Ignore/forbid kprobes attach on very low level functions marked by this attribute: */
#ifdef CONFIG_KPROBES
# define __kprobes __attribute__((__section__(".kprobes.text")))

18
include/linux/kernel.h
View file

@ -813,13 +813,15 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
#endif
/* Permissions on a sysfs file: you didn't miss the 0 prefix did you? */
#define VERIFY_OCTAL_PERMISSIONS(perms) \
(BUILD_BUG_ON_ZERO((perms) < 0) + \
BUILD_BUG_ON_ZERO((perms) > 0777) + \
/* User perms >= group perms >= other perms */ \
BUILD_BUG_ON_ZERO(((perms) >> 6) < (((perms) >> 3) & 7)) + \
BUILD_BUG_ON_ZERO((((perms) >> 3) & 7) < ((perms) & 7)) + \
/* Other writable? Generally considered a bad idea. */ \
BUILD_BUG_ON_ZERO((perms) & 2) + \
#define VERIFY_OCTAL_PERMISSIONS(perms) \
(BUILD_BUG_ON_ZERO((perms) < 0) + \
BUILD_BUG_ON_ZERO((perms) > 0777) + \
/* USER_READABLE >= GROUP_READABLE >= OTHER_READABLE */ \
BUILD_BUG_ON_ZERO((((perms) >> 6) & 4) < (((perms) >> 3) & 4)) + \
BUILD_BUG_ON_ZERO((((perms) >> 3) & 4) < ((perms) & 4)) + \
/* USER_WRITABLE >= GROUP_WRITABLE */ \
BUILD_BUG_ON_ZERO((((perms) >> 6) & 2) < (((perms) >> 3) & 2)) + \
/* OTHER_WRITABLE? Generally considered a bad idea. */ \
BUILD_BUG_ON_ZERO((perms) & 2) + \
(perms))
#endif

46
include/linux/module.h
View file

@ -17,6 +17,7 @@
#include <linux/moduleparam.h>
#include <linux/jump_label.h>
#include <linux/export.h>
#include <linux/rbtree_latch.h>
#include <linux/percpu.h>
#include <asm/module.h>
@ -210,6 +211,13 @@ enum module_state {
MODULE_STATE_UNFORMED, /* Still setting it up. */
};
struct module;
struct mod_tree_node {
struct module *mod;
struct latch_tree_node node;
};
struct module {
enum module_state state;
@ -232,6 +240,9 @@ struct module {
unsigned int num_syms;
/* Kernel parameters. */
#ifdef CONFIG_SYSFS
struct mutex param_lock;
#endif
struct kernel_param *kp;
unsigned int num_kp;
@ -271,8 +282,15 @@ struct module {
/* Startup function. */
int (*init)(void);
/* If this is non-NULL, vfree after init() returns */
void *module_init;
/*
* If this is non-NULL, vfree() after init() returns.
*
* Cacheline align here, such that:
* module_init, module_core, init_size, core_size,
* init_text_size, core_text_size and mtn_core::{mod,node[0]}
* are on the same cacheline.
*/
void *module_init ____cacheline_aligned;
/* Here is the actual code + data, vfree'd on unload. */
void *module_core;
@ -283,6 +301,16 @@ struct module {
/* The size of the executable code in each section. */
unsigned int init_text_size, core_text_size;
#ifdef CONFIG_MODULES_TREE_LOOKUP
/*
* We want mtn_core::{mod,node[0]} to be in the same cacheline as the
* above entries such that a regular lookup will only touch one
* cacheline.
*/
struct mod_tree_node mtn_core;
struct mod_tree_node mtn_init;
#endif
/* Size of RO sections of the module (text+rodata) */
unsigned int init_ro_size, core_ro_size;
@ -369,7 +397,7 @@ struct module {
ctor_fn_t *ctors;
unsigned int num_ctors;
#endif
};
} ____cacheline_aligned;
#ifndef MODULE_ARCH_INIT
#define MODULE_ARCH_INIT {}
#endif
@ -423,14 +451,22 @@ struct symsearch {
bool unused;
};
/* Search for an exported symbol by name. */
/*
* Search for an exported symbol by name.
*
* Must be called with module_mutex held or preemption disabled.
*/
const struct kernel_symbol *find_symbol(const char *name,
struct module **owner,
const unsigned long **crc,
bool gplok,
bool warn);
/* Walk the exported symbol table */
/*
* Walk the exported symbol table
*
* Must be called with module_mutex held or preemption disabled.
*/
bool each_symbol_section(bool (*fn)(const struct symsearch *arr,
struct module *owner,
void *data), void *data);

99
include/linux/moduleparam.h
View file

@ -67,8 +67,9 @@ enum {
struct kernel_param {
const char *name;
struct module *mod;
const struct kernel_param_ops *ops;
u16 perm;
const u16 perm;
s8 level;
u8 flags;
union {
@ -108,7 +109,7 @@ struct kparam_array
*
* @perm is 0 if the the variable is not to appear in sysfs, or 0444
* for world-readable, 0644 for root-writable, etc. Note that if it
* is writable, you may need to use kparam_block_sysfs_write() around
* is writable, you may need to use kernel_param_lock() around
* accesses (esp. charp, which can be kfreed when it changes).
*
* The @type is simply pasted to refer to a param_ops_##type and a
@ -216,16 +217,16 @@ struct kparam_array
parameters. */
#define __module_param_call(prefix, name, ops, arg, perm, level, flags) \
/* Default value instead of permissions? */ \
static const char __param_str_##name[] = prefix #name; \
static const char __param_str_##name[] = prefix #name; \
static struct kernel_param __moduleparam_const __param_##name \
__used \
__attribute__ ((unused,__section__ ("__param"),aligned(sizeof(void *)))) \
= { __param_str_##name, ops, VERIFY_OCTAL_PERMISSIONS(perm), \
level, flags, { arg } }
= { __param_str_##name, THIS_MODULE, ops, \
VERIFY_OCTAL_PERMISSIONS(perm), level, flags, { arg } }
/* Obsolete - use module_param_cb() */
#define module_param_call(name, set, get, arg, perm) \
static struct kernel_param_ops __param_ops_##name = \
static const struct kernel_param_ops __param_ops_##name = \
{ .flags = 0, (void *)set, (void *)get }; \
__module_param_call(MODULE_PARAM_PREFIX, \
name, &__param_ops_##name, arg, \
@ -238,58 +239,14 @@ __check_old_set_param(int (*oldset)(const char *, struct kernel_param *))
return 0;
}
/**
* kparam_block_sysfs_write - make sure a parameter isn't written via sysfs.
* @name: the name of the parameter
*
* There's no point blocking write on a paramter that isn't writable via sysfs!
*/
#define kparam_block_sysfs_write(name) \
do { \
BUG_ON(!(__param_##name.perm & 0222)); \
__kernel_param_lock(); \
} while (0)
/**
* kparam_unblock_sysfs_write - allows sysfs to write to a parameter again.
* @name: the name of the parameter
*/
#define kparam_unblock_sysfs_write(name) \
do { \
BUG_ON(!(__param_##name.perm & 0222)); \
__kernel_param_unlock(); \
} while (0)
/**
* kparam_block_sysfs_read - make sure a parameter isn't read via sysfs.
* @name: the name of the parameter
*
* This also blocks sysfs writes.
*/
#define kparam_block_sysfs_read(name) \
do { \
BUG_ON(!(__param_##name.perm & 0444)); \
__kernel_param_lock(); \
} while (0)
/**
* kparam_unblock_sysfs_read - allows sysfs to read a parameter again.
* @name: the name of the parameter
*/
#define kparam_unblock_sysfs_read(name) \
do { \
BUG_ON(!(__param_##name.perm & 0444)); \
__kernel_param_unlock(); \
} while (0)
#ifdef CONFIG_SYSFS
extern void __kernel_param_lock(void);
extern void __kernel_param_unlock(void);
extern void kernel_param_lock(struct module *mod);
extern void kernel_param_unlock(struct module *mod);
#else
static inline void __kernel_param_lock(void)
static inline void kernel_param_lock(struct module *mod)
{
}
static inline void __kernel_param_unlock(void)
static inline void kernel_param_unlock(struct module *mod)
{
}
#endif
@ -386,64 +343,70 @@ static inline void destroy_params(const struct kernel_param *params,
#define __param_check(name, p, type) \
static inline type __always_unused *__check_##name(void) { return(p); }
extern struct kernel_param_ops param_ops_byte;
extern const struct kernel_param_ops param_ops_byte;
extern int param_set_byte(const char *val, const struct kernel_param *kp);
extern int param_get_byte(char *buffer, const struct kernel_param *kp);
#define param_check_byte(name, p) __param_check(name, p, unsigned char)
extern struct kernel_param_ops param_ops_short;
extern const struct kernel_param_ops param_ops_short;
extern int param_set_short(const char *val, const struct kernel_param *kp);
extern int param_get_short(char *buffer, const struct kernel_param *kp);
#define param_check_short(name, p) __param_check(name, p, short)
extern struct kernel_param_ops param_ops_ushort;
extern const struct kernel_param_ops param_ops_ushort;
extern int param_set_ushort(const char *val, const struct kernel_param *kp);
extern int param_get_ushort(char *buffer, const struct kernel_param *kp);
#define param_check_ushort(name, p) __param_check(name, p, unsigned short)
extern struct kernel_param_ops param_ops_int;
extern const struct kernel_param_ops param_ops_int;
extern int param_set_int(const char *val, const struct kernel_param *kp);
extern int param_get_int(char *buffer, const struct kernel_param *kp);
#define param_check_int(name, p) __param_check(name, p, int)
extern struct kernel_param_ops param_ops_uint;
extern const struct kernel_param_ops param_ops_uint;
extern int param_set_uint(const char *val, const struct kernel_param *kp);
extern int param_get_uint(char *buffer, const struct kernel_param *kp);
#define param_check_uint(name, p) __param_check(name, p, unsigned int)
extern struct kernel_param_ops param_ops_long;
extern const struct kernel_param_ops param_ops_long;
extern int param_set_long(const char *val, const struct kernel_param *kp);
extern int param_get_long(char *buffer, const struct kernel_param *kp);
#define param_check_long(name, p) __param_check(name, p, long)
extern struct kernel_param_ops param_ops_ulong;
extern const struct kernel_param_ops param_ops_ulong;
extern int param_set_ulong(const char *val, const struct kernel_param *kp);
extern int param_get_ulong(char *buffer, const struct kernel_param *kp);
#define param_check_ulong(name, p) __param_check(name, p, unsigned long)
extern struct kernel_param_ops param_ops_ullong;
extern const struct kernel_param_ops param_ops_ullong;
extern int param_set_ullong(const char *val, const struct kernel_param *kp);
extern int param_get_ullong(char *buffer, const struct kernel_param *kp);
#define param_check_ullong(name, p) __param_check(name, p, unsigned long long)
extern struct kernel_param_ops param_ops_charp;
extern const struct kernel_param_ops param_ops_charp;
extern int param_set_charp(const char *val, const struct kernel_param *kp);
extern int param_get_charp(char *buffer, const struct kernel_param *kp);
#define param_check_charp(name, p) __param_check(name, p, char *)
/* We used to allow int as well as bool. We're taking that away! */
extern struct kernel_param_ops param_ops_bool;
extern const struct kernel_param_ops param_ops_bool;
extern int param_set_bool(const char *val, const struct kernel_param *kp);
extern int param_get_bool(char *buffer, const struct kernel_param *kp);
#define param_check_bool(name, p) __param_check(name, p, bool)
extern struct kernel_param_ops param_ops_invbool;
extern const struct kernel_param_ops param_ops_bool_enable_only;
extern int param_set_bool_enable_only(const char *val,
const struct kernel_param *kp);
/* getter is the same as for the regular bool */
#define param_check_bool_enable_only param_check_bool
extern const struct kernel_param_ops param_ops_invbool;
extern int param_set_invbool(const char *val, const struct kernel_param *kp);
extern int param_get_invbool(char *buffer, const struct kernel_param *kp);
#define param_check_invbool(name, p) __param_check(name, p, bool)
/* An int, which can only be set like a bool (though it shows as an int). */
extern struct kernel_param_ops param_ops_bint;
extern const struct kernel_param_ops param_ops_bint;
extern int param_set_bint(const char *val, const struct kernel_param *kp);
#define param_get_bint param_get_int
#define param_check_bint param_check_int
@ -487,9 +450,9 @@ extern int param_set_bint(const char *val, const struct kernel_param *kp);
perm, -1, 0); \
__MODULE_PARM_TYPE(name, "array of " #type)
extern struct kernel_param_ops param_array_ops;
extern const struct kernel_param_ops param_array_ops;
extern struct kernel_param_ops param_ops_string;
extern const struct kernel_param_ops param_ops_string;
extern int param_set_copystring(const char *val, const struct kernel_param *);
extern int param_get_string(char *buffer, const struct kernel_param *kp);

16
include/linux/rbtree.h
View file

@ -31,6 +31,7 @@
#include <linux/kernel.h>
#include <linux/stddef.h>
#include <linux/rcupdate.h>
struct rb_node {
unsigned long __rb_parent_color;
@ -73,11 +74,11 @@ extern struct rb_node *rb_first_postorder(const struct rb_root *);
extern struct rb_node *rb_next_postorder(const struct rb_node *);
/* Fast replacement of a single node without remove/rebalance/add/rebalance */
extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
extern void rb_replace_node(struct rb_node *victim, struct rb_node *new,
struct rb_root *root);
static inline void rb_link_node(struct rb_node * node, struct rb_node * parent,
struct rb_node ** rb_link)
static inline void rb_link_node(struct rb_node *node, struct rb_node *parent,
struct rb_node **rb_link)
{
node->__rb_parent_color = (unsigned long)parent;
node->rb_left = node->rb_right = NULL;
@ -85,6 +86,15 @@ static inline void rb_link_node(struct rb_node * node, struct rb_node * parent,
*rb_link = node;
}
static inline void rb_link_node_rcu(struct rb_node *node, struct rb_node *parent,
struct rb_node **rb_link)
{
node->__rb_parent_color = (unsigned long)parent;
node->rb_left = node->rb_right = NULL;
rcu_assign_pointer(*rb_link, node);
}
#define rb_entry_safe(ptr, type, member) \
({ typeof(ptr) ____ptr = (ptr); \
____ptr ? rb_entry(____ptr, type, member) : NULL; \

21
include/linux/rbtree_augmented.h
View file

@ -123,11 +123,11 @@ __rb_change_child(struct rb_node *old, struct rb_node *new,
{
if (parent) {
if (parent->rb_left == old)
parent->rb_left = new;
WRITE_ONCE(parent->rb_left, new);
else
parent->rb_right = new;
WRITE_ONCE(parent->rb_right, new);
} else
root->rb_node = new;
WRITE_ONCE(root->rb_node, new);
}
extern void __rb_erase_color(struct rb_node *parent, struct rb_root *root,
@ -137,7 +137,8 @@ static __always_inline struct rb_node *
__rb_erase_augmented(struct rb_node *node, struct rb_root *root,
const struct rb_augment_callbacks *augment)
{
struct rb_node *child = node->rb_right, *tmp = node->rb_left;
struct rb_node *child = node->rb_right;
struct rb_node *tmp = node->rb_left;
struct rb_node *parent, *rebalance;
unsigned long pc;
@ -167,6 +168,7 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
tmp = parent;
} else {
struct rb_node *successor = child, *child2;
tmp = child->rb_left;
if (!tmp) {
/*
@ -180,6 +182,7 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
*/
parent = successor;
child2 = successor->rb_right;
augment->copy(node, successor);
} else {
/*
@ -201,19 +204,23 @@ __rb_erase_augmented(struct rb_node *node, struct rb_root *root,
successor = tmp;
tmp = tmp->rb_left;
} while (tmp);
parent->rb_left = child2 = successor->rb_right;
successor->rb_right = child;
child2 = successor->rb_right;
WRITE_ONCE(parent->rb_left, child2);
WRITE_ONCE(successor->rb_right, child);
rb_set_parent(child, successor);
augment->copy(node, successor);
augment->propagate(parent, successor);
}
successor->rb_left = tmp = node->rb_left;
tmp = node->rb_left;
WRITE_ONCE(successor->rb_left, tmp);
rb_set_parent(tmp, successor);
pc = node->__rb_parent_color;
tmp = __rb_parent(pc);
__rb_change_child(node, successor, tmp, root);
if (child2) {
successor->__rb_parent_color = pc;
rb_set_parent_color(child2, parent, RB_BLACK);

212
include/linux/rbtree_latch.h Normal file
View file

@ -0,0 +1,212 @@
/*
* Latched RB-trees
*
* Copyright (C) 2015 Intel Corp., Peter Zijlstra <peterz@infradead.org>
*
* Since RB-trees have non-atomic modifications they're not immediately suited
* for RCU/lockless queries. Even though we made RB-tree lookups non-fatal for
* lockless lookups; we cannot guarantee they return a correct result.
*
* The simplest solution is a seqlock + RB-tree, this will allow lockless
* lookups; but has the constraint (inherent to the seqlock) that read sides
* cannot nest in write sides.
*
* If we need to allow unconditional lookups (say as required for NMI context
* usage) we need a more complex setup; this data structure provides this by
* employing the latch technique -- see @raw_write_seqcount_latch -- to
* implement a latched RB-tree which does allow for unconditional lookups by
* virtue of always having (at least) one stable copy of the tree.
*
* However, while we have the guarantee that there is at all times one stable
* copy, this does not guarantee an iteration will not observe modifications.
* What might have been a stable copy at the start of the iteration, need not
* remain so for the duration of the iteration.
*
* Therefore, this does require a lockless RB-tree iteration to be non-fatal;
* see the comment in lib/rbtree.c. Note however that we only require the first
* condition -- not seeing partial stores -- because the latch thing isolates
* us from loops. If we were to interrupt a modification the lookup would be
* pointed at the stable tree and complete while the modification was halted.
*/
#ifndef RB_TREE_LATCH_H
#define RB_TREE_LATCH_H
#include <linux/rbtree.h>
#include <linux/seqlock.h>
struct latch_tree_node {
struct rb_node node[2];
};
struct latch_tree_root {
seqcount_t seq;
struct rb_root tree[2];
};
/**
* latch_tree_ops - operators to define the tree order
* @less: used for insertion; provides the (partial) order between two elements.
* @comp: used for lookups; provides the order between the search key and an element.
*
* The operators are related like:
*
* comp(a->key,b) < 0 := less(a,b)
* comp(a->key,b) > 0 := less(b,a)
* comp(a->key,b) == 0 := !less(a,b) && !less(b,a)
*
* If these operators define a partial order on the elements we make no
* guarantee on which of the elements matching the key is found. See
* latch_tree_find().
*/
struct latch_tree_ops {
bool (*less)(struct latch_tree_node *a, struct latch_tree_node *b);
int (*comp)(void *key, struct latch_tree_node *b);
};
static __always_inline struct latch_tree_node *
__lt_from_rb(struct rb_node *node, int idx)
{
return container_of(node, struct latch_tree_node, node[idx]);
}
static __always_inline void
__lt_insert(struct latch_tree_node *ltn, struct latch_tree_root *ltr, int idx,
bool (*less)(struct latch_tree_node *a, struct latch_tree_node *b))
{
struct rb_root *root = &ltr->tree[idx];
struct rb_node **link = &root->rb_node;
struct rb_node *node = &ltn->node[idx];
struct rb_node *parent = NULL;
struct latch_tree_node *ltp;
while (*link) {
parent = *link;
ltp = __lt_from_rb(parent, idx);
if (less(ltn, ltp))
link = &parent->rb_left;
else
link = &parent->rb_right;
}
rb_link_node_rcu(node, parent, link);
rb_insert_color(node, root);
}
static __always_inline void
__lt_erase(struct latch_tree_node *ltn, struct latch_tree_root *ltr, int idx)
{
rb_erase(&ltn->node[idx], &ltr->tree[idx]);
}
static __always_inline struct latch_tree_node *
__lt_find(void *key, struct latch_tree_root *ltr, int idx,
int (*comp)(void *key, struct latch_tree_node *node))
{
struct rb_node *node = rcu_dereference_raw(ltr->tree[idx].rb_node);
struct latch_tree_node *ltn;
int c;
while (node) {
ltn = __lt_from_rb(node, idx);
c = comp(key, ltn);
if (c < 0)
node = rcu_dereference_raw(node->rb_left);
else if (c > 0)
node = rcu_dereference_raw(node->rb_right);
else
return ltn;
}
return NULL;
}
/**
* latch_tree_insert() - insert @node into the trees @root
* @node: nodes to insert
* @root: trees to insert @node into
* @ops: operators defining the node order
*
* It inserts @node into @root in an ordered fashion such that we can always
* observe one complete tree. See the comment for raw_write_seqcount_latch().
*
* The inserts use rcu_assign_pointer() to publish the element such that the
* tree structure is stored before we can observe the new @node.
*
* All modifications (latch_tree_insert, latch_tree_remove) are assumed to be
* serialized.
*/
static __always_inline void
latch_tree_insert(struct latch_tree_node *node,
struct latch_tree_root *root,
const struct latch_tree_ops *ops)
{
raw_write_seqcount_latch(&root->seq);
__lt_insert(node, root, 0, ops->less);
raw_write_seqcount_latch(&root->seq);
__lt_insert(node, root, 1, ops->less);
}
/**
* latch_tree_erase() - removes @node from the trees @root
* @node: nodes to remote
* @root: trees to remove @node from
* @ops: operators defining the node order
*
* Removes @node from the trees @root in an ordered fashion such that we can
* always observe one complete tree. See the comment for
* raw_write_seqcount_latch().
*
* It is assumed that @node will observe one RCU quiescent state before being
* reused of freed.
*
* All modifications (latch_tree_insert, latch_tree_remove) are assumed to be
* serialized.
*/
static __always_inline void
latch_tree_erase(struct latch_tree_node *node,
struct latch_tree_root *root,
const struct latch_tree_ops *ops)
{
raw_write_seqcount_latch(&root->seq);
__lt_erase(node, root, 0);
raw_write_seqcount_latch(&root->seq);
__lt_erase(node, root, 1);
}
/**
* latch_tree_find() - find the node matching @key in the trees @root
* @key: search key
* @root: trees to search for @key
* @ops: operators defining the node order
*
* Does a lockless lookup in the trees @root for the node matching @key.
*
* It is assumed that this is called while holding the appropriate RCU read
* side lock.
*
* If the operators define a partial order on the elements (there are multiple
* elements which have the same key value) it is undefined which of these
* elements will be found. Nor is it possible to iterate the tree to find
* further elements with the same key value.
*
* Returns: a pointer to the node matching @key or NULL.
*/
static __always_inline struct latch_tree_node *
latch_tree_find(void *key, struct latch_tree_root *root,
const struct latch_tree_ops *ops)
{
struct latch_tree_node *node;
unsigned int seq;
do {
seq = raw_read_seqcount_latch(&root->seq);
node = __lt_find(key, root, seq & 1, ops->comp);
} while (read_seqcount_retry(&root->seq, seq));
return node;
}
#endif /* RB_TREE_LATCH_H */

15
include/linux/rcupdate.h
View file

@ -632,21 +632,6 @@ static inline void rcu_preempt_sleep_check(void)
*/
#define RCU_INITIALIZER(v) (typeof(*(v)) __force __rcu *)(v)
/**
* lockless_dereference() - safely load a pointer for later dereference
* @p: The pointer to load
*
* Similar to rcu_dereference(), but for situations where the pointed-to
* object's lifetime is managed by something other than RCU. That
* "something other" might be reference counting or simple immortality.
*/
#define lockless_dereference(p) \
({ \
typeof(p) _________p1 = READ_ONCE(p); \
smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
(_________p1); \
})
/**
* rcu_assign_pointer() - assign to RCU-protected pointer
* @p: pointer to assign to

81
include/linux/seqlock.h
View file

@ -35,6 +35,7 @@
#include <linux/spinlock.h>
#include <linux/preempt.h>
#include <linux/lockdep.h>
#include <linux/compiler.h>
#include <asm/processor.h>
/*
@ -274,9 +275,87 @@ static inline void raw_write_seqcount_barrier(seqcount_t *s)
s->sequence++;
}
/*
static inline int raw_read_seqcount_latch(seqcount_t *s)
{
return lockless_dereference(s->sequence);
}
/**
* raw_write_seqcount_latch - redirect readers to even/odd copy
* @s: pointer to seqcount_t
*
* The latch technique is a multiversion concurrency control method that allows
* queries during non-atomic modifications. If you can guarantee queries never
* interrupt the modification -- e.g. the concurrency is strictly between CPUs
* -- you most likely do not need this.
*
* Where the traditional RCU/lockless data structures rely on atomic
* modifications to ensure queries observe either the old or the new state the
* latch allows the same for non-atomic updates. The trade-off is doubling the
* cost of storage; we have to maintain two copies of the entire data
* structure.
*
* Very simply put: we first modify one copy and then the other. This ensures
* there is always one copy in a stable state, ready to give us an answer.
*
* The basic form is a data structure like:
*
* struct latch_struct {
* seqcount_t seq;
* struct data_struct data[2];
* };
*
* Where a modification, which is assumed to be externally serialized, does the
* following:
*
* void latch_modify(struct latch_struct *latch, ...)
* {
* smp_wmb(); <- Ensure that the last data[1] update is visible
* latch->seq++;
* smp_wmb(); <- Ensure that the seqcount update is visible
*
* modify(latch->data[0], ...);
*
* smp_wmb(); <- Ensure that the data[0] update is visible
* latch->seq++;
* smp_wmb(); <- Ensure that the seqcount update is visible
*
* modify(latch->data[1], ...);
* }
*
* The query will have a form like:
*
* struct entry *latch_query(struct latch_struct *latch, ...)
* {
* struct entry *entry;
* unsigned seq, idx;
*
* do {
* seq = lockless_dereference(latch->seq);
*
* idx = seq & 0x01;
* entry = data_query(latch->data[idx], ...);
*
* smp_rmb();
* } while (seq != latch->seq);
*
* return entry;
* }
*
* So during the modification, queries are first redirected to data[1]. Then we
* modify data[0]. When that is complete, we redirect queries back to data[0]
* and we can modify data[1].
*
* NOTE: The non-requirement for atomic modifications does _NOT_ include
* the publishing of new entries in the case where data is a dynamic
* data structure.
*
* An iteration might start in data[0] and get suspended long enough
* to miss an entire modification sequence, once it resumes it might
* observe the new entry.
*
* NOTE: When data is a dynamic data structure; one should use regular RCU
* patterns to manage the lifetimes of the objects within.
*/
static inline void raw_write_seqcount_latch(seqcount_t *s)
{