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Merge branch 'for-mingo' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

Browse Source 
Pull RCU updates from Paul E. McKenney:

 - Documentation updates.

 - Miscellaneous fixes.

 - Parallelize SRCU callback handling (plus overlapping patches).

Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ingo Molnar
2017-04-23 11:12:44 +02:00
parent 94836ecf1e f2094107ac
commit 58d30c36d4
71 changed files with 3637 additions and 1116 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/dma-fence.h
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@@ -229,7 +229,7 @@ static inline struct dma_fence *dma_fence_get_rcu(struct dma_fence *fence)
*
* Function returns NULL if no refcount could be obtained, or the fence.
* This function handles acquiring a reference to a fence that may be
* reallocated within the RCU grace period (such as with SLAB_DESTROY_BY_RCU),
* reallocated within the RCU grace period (such as with SLAB_TYPESAFE_BY_RCU),
* so long as the caller is using RCU on the pointer to the fence.
*
* An alternative mechanism is to employ a seqlock to protect a bunch of
@@ -257,7 +257,7 @@ dma_fence_get_rcu_safe(struct dma_fence * __rcu *fencep)
* have successfully acquire a reference to it. If it no
* longer matches, we are holding a reference to some other
* reallocated pointer. This is possible if the allocator
* is using a freelist like SLAB_DESTROY_BY_RCU where the
* is using a freelist like SLAB_TYPESAFE_BY_RCU where the
* fence remains valid for the RCU grace period, but it
* may be reallocated. When using such allocators, we are
* responsible for ensuring the reference we get is to

4
include/linux/kvm_host.h
View File

@@ -375,8 +375,6 @@ struct kvm {
struct mutex slots_lock;
struct mm_struct *mm; /* userspace tied to this vm */
struct kvm_memslots *memslots[KVM_ADDRESS_SPACE_NUM];
struct srcu_struct srcu;
struct srcu_struct irq_srcu;
struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
/*
@@ -429,6 +427,8 @@ struct kvm {
struct list_head devices;
struct dentry *debugfs_dentry;
struct kvm_stat_data **debugfs_stat_data;
struct srcu_struct srcu;
struct srcu_struct irq_srcu;
};
#define kvm_err(fmt, ...) \

99
include/linux/rcu_node_tree.h Normal file
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@@ -0,0 +1,99 @@
/*
* RCU node combining tree definitions. These are used to compute
* global attributes while avoiding common-case global contention. A key
* property that these computations rely on is a tournament-style approach
* where only one of the tasks contending a lower level in the tree need
* advance to the next higher level. If properly configured, this allows
* unlimited scalability while maintaining a constant level of contention
* on the root node.
*
* 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 IBM Corporation, 2017
*
* Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*/
#ifndef __LINUX_RCU_NODE_TREE_H
#define __LINUX_RCU_NODE_TREE_H
/*
* Define shape of hierarchy based on NR_CPUS, CONFIG_RCU_FANOUT, and
* CONFIG_RCU_FANOUT_LEAF.
* In theory, it should be possible to add more levels straightforwardly.
* In practice, this did work well going from three levels to four.
* Of course, your mileage may vary.
*/
#ifdef CONFIG_RCU_FANOUT
#define RCU_FANOUT CONFIG_RCU_FANOUT
#else /* #ifdef CONFIG_RCU_FANOUT */
# ifdef CONFIG_64BIT
# define RCU_FANOUT 64
# else
# define RCU_FANOUT 32
# endif
#endif /* #else #ifdef CONFIG_RCU_FANOUT */
#ifdef CONFIG_RCU_FANOUT_LEAF
#define RCU_FANOUT_LEAF CONFIG_RCU_FANOUT_LEAF
#else /* #ifdef CONFIG_RCU_FANOUT_LEAF */
#define RCU_FANOUT_LEAF 16
#endif /* #else #ifdef CONFIG_RCU_FANOUT_LEAF */
#define RCU_FANOUT_1 (RCU_FANOUT_LEAF)
#define RCU_FANOUT_2 (RCU_FANOUT_1 * RCU_FANOUT)
#define RCU_FANOUT_3 (RCU_FANOUT_2 * RCU_FANOUT)
#define RCU_FANOUT_4 (RCU_FANOUT_3 * RCU_FANOUT)
#if NR_CPUS <= RCU_FANOUT_1
# define RCU_NUM_LVLS 1
# define NUM_RCU_LVL_0 1
# define NUM_RCU_NODES NUM_RCU_LVL_0
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0 }
# define RCU_NODE_NAME_INIT { "rcu_node_0" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" }
#elif NR_CPUS <= RCU_FANOUT_2
# define RCU_NUM_LVLS 2
# define NUM_RCU_LVL_0 1
# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
# define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1)
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1 }
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" }
#elif NR_CPUS <= RCU_FANOUT_3
# define RCU_NUM_LVLS 3
# define NUM_RCU_LVL_0 1
# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
# define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2)
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 }
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" }
#elif NR_CPUS <= RCU_FANOUT_4
# define RCU_NUM_LVLS 4
# define NUM_RCU_LVL_0 1
# define NUM_RCU_LVL_1 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_3)
# define NUM_RCU_LVL_2 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_2)
# define NUM_RCU_LVL_3 DIV_ROUND_UP(NR_CPUS, RCU_FANOUT_1)
# define NUM_RCU_NODES (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3)
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 }
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" }
#else
# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
#endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */
#endif /* __LINUX_RCU_NODE_TREE_H */

712
include/linux/rcu_segcblist.h Normal file
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@@ -0,0 +1,712 @@
/*
* RCU segmented callback lists
*
* 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 IBM Corporation, 2017
*
* Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*/
#ifndef __KERNEL_RCU_SEGCBLIST_H
#define __KERNEL_RCU_SEGCBLIST_H
/* Simple unsegmented callback lists. */
struct rcu_cblist {
struct rcu_head *head;
struct rcu_head **tail;
long len;
long len_lazy;
};
#define RCU_CBLIST_INITIALIZER(n) { .head = NULL, .tail = &n.head }
/* Initialize simple callback list. */
static inline void rcu_cblist_init(struct rcu_cblist *rclp)
{
rclp->head = NULL;
rclp->tail = &rclp->head;
rclp->len = 0;
rclp->len_lazy = 0;
}
/* Is simple callback list empty? */
static inline bool rcu_cblist_empty(struct rcu_cblist *rclp)
{
return !rclp->head;
}
/* Return number of callbacks in simple callback list. */
static inline long rcu_cblist_n_cbs(struct rcu_cblist *rclp)
{
return rclp->len;
}
/* Return number of lazy callbacks in simple callback list. */
static inline long rcu_cblist_n_lazy_cbs(struct rcu_cblist *rclp)
{
return rclp->len_lazy;
}
/*
* Debug function to actually count the number of callbacks.
* If the number exceeds the limit specified, return -1.
*/
static inline long rcu_cblist_count_cbs(struct rcu_cblist *rclp, long lim)
{
int cnt = 0;
struct rcu_head **rhpp = &rclp->head;
for (;;) {
if (!*rhpp)
return cnt;
if (++cnt > lim)
return -1;
rhpp = &(*rhpp)->next;
}
}
/*
* Dequeue the oldest rcu_head structure from the specified callback
* list. This function assumes that the callback is non-lazy, but
* the caller can later invoke rcu_cblist_dequeued_lazy() if it
* finds otherwise (and if it cares about laziness). This allows
* different users to have different ways of determining laziness.
*/
static inline struct rcu_head *rcu_cblist_dequeue(struct rcu_cblist *rclp)
{
struct rcu_head *rhp;
rhp = rclp->head;
if (!rhp)
return NULL;
rclp->len--;
rclp->head = rhp->next;
if (!rclp->head)
rclp->tail = &rclp->head;
return rhp;
}
/*
* Account for the fact that a previously dequeued callback turned out
* to be marked as lazy.
*/
static inline void rcu_cblist_dequeued_lazy(struct rcu_cblist *rclp)
{
rclp->len_lazy--;
}
/*
* Interim function to return rcu_cblist head pointer. Longer term, the
* rcu_cblist will be used more pervasively, removing the need for this
* function.
*/
static inline struct rcu_head *rcu_cblist_head(struct rcu_cblist *rclp)
{
return rclp->head;
}
/*
* Interim function to return rcu_cblist head pointer. Longer term, the
* rcu_cblist will be used more pervasively, removing the need for this
* function.
*/
static inline struct rcu_head **rcu_cblist_tail(struct rcu_cblist *rclp)
{
WARN_ON_ONCE(rcu_cblist_empty(rclp));
return rclp->tail;
}
/* Complicated segmented callback lists. ;-) */
/*
* Index values for segments in rcu_segcblist structure.
*
* The segments are as follows:
*
* [head, *tails[RCU_DONE_TAIL]):
* Callbacks whose grace period has elapsed, and thus can be invoked.
* [*tails[RCU_DONE_TAIL], *tails[RCU_WAIT_TAIL]):
* Callbacks waiting for the current GP from the current CPU's viewpoint.
* [*tails[RCU_WAIT_TAIL], *tails[RCU_NEXT_READY_TAIL]):
* Callbacks that arrived before the next GP started, again from
* the current CPU's viewpoint. These can be handled by the next GP.
* [*tails[RCU_NEXT_READY_TAIL], *tails[RCU_NEXT_TAIL]):
* Callbacks that might have arrived after the next GP started.
* There is some uncertainty as to when a given GP starts and
* ends, but a CPU knows the exact times if it is the one starting
* or ending the GP. Other CPUs know that the previous GP ends
* before the next one starts.
*
* Note that RCU_WAIT_TAIL cannot be empty unless RCU_NEXT_READY_TAIL is also
* empty.
*
* The ->gp_seq[] array contains the grace-period number at which the
* corresponding segment of callbacks will be ready to invoke. A given
* element of this array is meaningful only when the corresponding segment
* is non-empty, and it is never valid for RCU_DONE_TAIL (whose callbacks
* are already ready to invoke) or for RCU_NEXT_TAIL (whose callbacks have
* not yet been assigned a grace-period number).
*/
#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */
#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */
#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */
#define RCU_NEXT_TAIL 3
#define RCU_CBLIST_NSEGS 4
struct rcu_segcblist {
struct rcu_head *head;
struct rcu_head **tails[RCU_CBLIST_NSEGS];
unsigned long gp_seq[RCU_CBLIST_NSEGS];
long len;
long len_lazy;
};
#define RCU_SEGCBLIST_INITIALIZER(n) \
{ \
.head = NULL, \
.tails[RCU_DONE_TAIL] = &n.head, \
.tails[RCU_WAIT_TAIL] = &n.head, \
.tails[RCU_NEXT_READY_TAIL] = &n.head, \
.tails[RCU_NEXT_TAIL] = &n.head, \
}
/*
* Initialize an rcu_segcblist structure.
*/
static inline void rcu_segcblist_init(struct rcu_segcblist *rsclp)
{
int i;
BUILD_BUG_ON(RCU_NEXT_TAIL + 1 != ARRAY_SIZE(rsclp->gp_seq));
BUILD_BUG_ON(ARRAY_SIZE(rsclp->tails) != ARRAY_SIZE(rsclp->gp_seq));
rsclp->head = NULL;
for (i = 0; i < RCU_CBLIST_NSEGS; i++)
rsclp->tails[i] = &rsclp->head;
rsclp->len = 0;
rsclp->len_lazy = 0;
}
/*
* Is the specified rcu_segcblist structure empty?
*
* But careful! The fact that the ->head field is NULL does not
* necessarily imply that there are no callbacks associated with
* this structure. When callbacks are being invoked, they are
* removed as a group. If callback invocation must be preempted,
* the remaining callbacks will be added back to the list. Either
* way, the counts are updated later.
*
* So it is often the case that rcu_segcblist_n_cbs() should be used
* instead.
*/
static inline bool rcu_segcblist_empty(struct rcu_segcblist *rsclp)
{
return !rsclp->head;
}
/* Return number of callbacks in segmented callback list. */
static inline long rcu_segcblist_n_cbs(struct rcu_segcblist *rsclp)
{
return READ_ONCE(rsclp->len);
}
/* Return number of lazy callbacks in segmented callback list. */
static inline long rcu_segcblist_n_lazy_cbs(struct rcu_segcblist *rsclp)
{
return rsclp->len_lazy;
}
/* Return number of lazy callbacks in segmented callback list. */
static inline long rcu_segcblist_n_nonlazy_cbs(struct rcu_segcblist *rsclp)
{
return rsclp->len - rsclp->len_lazy;
}
/*
* Is the specified rcu_segcblist enabled, for example, not corresponding
* to an offline or callback-offloaded CPU?
*/
static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
{
return !!rsclp->tails[RCU_NEXT_TAIL];
}
/*
* Disable the specified rcu_segcblist structure, so that callbacks can
* no longer be posted to it. This structure must be empty.
*/
static inline void rcu_segcblist_disable(struct rcu_segcblist *rsclp)
{
WARN_ON_ONCE(!rcu_segcblist_empty(rsclp));
WARN_ON_ONCE(rcu_segcblist_n_cbs(rsclp));
WARN_ON_ONCE(rcu_segcblist_n_lazy_cbs(rsclp));
rsclp->tails[RCU_NEXT_TAIL] = NULL;
}
/*
* Is the specified segment of the specified rcu_segcblist structure
* empty of callbacks?
*/
static inline bool rcu_segcblist_segempty(struct rcu_segcblist *rsclp, int seg)
{
if (seg == RCU_DONE_TAIL)
return &rsclp->head == rsclp->tails[RCU_DONE_TAIL];
return rsclp->tails[seg - 1] == rsclp->tails[seg];
}
/*
* Are all segments following the specified segment of the specified
* rcu_segcblist structure empty of callbacks? (The specified
* segment might well contain callbacks.)
*/
static inline bool rcu_segcblist_restempty(struct rcu_segcblist *rsclp, int seg)
{
return !*rsclp->tails[seg];
}
/*
* Does the specified rcu_segcblist structure contain callbacks that
* are ready to be invoked?
*/
static inline bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp)
{
return rcu_segcblist_is_enabled(rsclp) &&
&rsclp->head != rsclp->tails[RCU_DONE_TAIL];
}
/*
* Does the specified rcu_segcblist structure contain callbacks that
* are still pending, that is, not yet ready to be invoked?
*/
static inline bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp)
{
return rcu_segcblist_is_enabled(rsclp) &&
!rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL);
}
/*
* Dequeue and return the first ready-to-invoke callback. If there
* are no ready-to-invoke callbacks, return NULL. Disables interrupts
* to avoid interference. Does not protect from interference from other
* CPUs or tasks.
*/
static inline struct rcu_head *
rcu_segcblist_dequeue(struct rcu_segcblist *rsclp)
{
unsigned long flags;
int i;
struct rcu_head *rhp;
local_irq_save(flags);
if (!rcu_segcblist_ready_cbs(rsclp)) {
local_irq_restore(flags);
return NULL;
}
rhp = rsclp->head;
BUG_ON(!rhp);
rsclp->head = rhp->next;
for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++) {
if (rsclp->tails[i] != &rhp->next)
break;
rsclp->tails[i] = &rsclp->head;
}
smp_mb(); /* Dequeue before decrement for rcu_barrier(). */
WRITE_ONCE(rsclp->len, rsclp->len - 1);
local_irq_restore(flags);
return rhp;
}
/*
* Account for the fact that a previously dequeued callback turned out
* to be marked as lazy.
*/
static inline void rcu_segcblist_dequeued_lazy(struct rcu_segcblist *rsclp)
{
unsigned long flags;
local_irq_save(flags);
rsclp->len_lazy--;
local_irq_restore(flags);
}
/*
* Return a pointer to the first callback in the specified rcu_segcblist
* structure. This is useful for diagnostics.
*/
static inline struct rcu_head *
rcu_segcblist_first_cb(struct rcu_segcblist *rsclp)
{
if (rcu_segcblist_is_enabled(rsclp))
return rsclp->head;
return NULL;
}
/*
* Return a pointer to the first pending callback in the specified
* rcu_segcblist structure. This is useful just after posting a given
* callback -- if that callback is the first pending callback, then
* you cannot rely on someone else having already started up the required
* grace period.
*/
static inline struct rcu_head *
rcu_segcblist_first_pend_cb(struct rcu_segcblist *rsclp)
{
if (rcu_segcblist_is_enabled(rsclp))
return *rsclp->tails[RCU_DONE_TAIL];
return NULL;
}
/*
* Does the specified rcu_segcblist structure contain callbacks that
* have not yet been processed beyond having been posted, that is,
* does it contain callbacks in its last segment?
*/
static inline bool rcu_segcblist_new_cbs(struct rcu_segcblist *rsclp)
{
return rcu_segcblist_is_enabled(rsclp) &&
!rcu_segcblist_restempty(rsclp, RCU_NEXT_READY_TAIL);
}
/*
* Enqueue the specified callback onto the specified rcu_segcblist
* structure, updating accounting as needed. Note that the ->len
* field may be accessed locklessly, hence the WRITE_ONCE().
* The ->len field is used by rcu_barrier() and friends to determine
* if it must post a callback on this structure, and it is OK
* for rcu_barrier() to sometimes post callbacks needlessly, but
* absolutely not OK for it to ever miss posting a callback.
*/
static inline void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
struct rcu_head *rhp, bool lazy)
{
WRITE_ONCE(rsclp->len, rsclp->len + 1); /* ->len sampled locklessly. */
if (lazy)
rsclp->len_lazy++;
smp_mb(); /* Ensure counts are updated before callback is enqueued. */
rhp->next = NULL;
*rsclp->tails[RCU_NEXT_TAIL] = rhp;
rsclp->tails[RCU_NEXT_TAIL] = &rhp->next;
}
/*
* Entrain the specified callback onto the specified rcu_segcblist at
* the end of the last non-empty segment. If the entire rcu_segcblist
* is empty, make no change, but return false.
*
* This is intended for use by rcu_barrier()-like primitives, -not-
* for normal grace-period use. IMPORTANT: The callback you enqueue
* will wait for all prior callbacks, NOT necessarily for a grace
* period. You have been warned.
*/
static inline bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
struct rcu_head *rhp, bool lazy)
{
int i;
if (rcu_segcblist_n_cbs(rsclp) == 0)
return false;
WRITE_ONCE(rsclp->len, rsclp->len + 1);
if (lazy)
rsclp->len_lazy++;
smp_mb(); /* Ensure counts are updated before callback is entrained. */
rhp->next = NULL;
for (i = RCU_NEXT_TAIL; i > RCU_DONE_TAIL; i--)
if (rsclp->tails[i] != rsclp->tails[i - 1])
break;
*rsclp->tails[i] = rhp;
for (; i <= RCU_NEXT_TAIL; i++)
rsclp->tails[i] = &rhp->next;
return true;
}
/*
* Extract only the counts from the specified rcu_segcblist structure,
* and place them in the specified rcu_cblist structure. This function
* supports both callback orphaning and invocation, hence the separation
* of counts and callbacks. (Callbacks ready for invocation must be
* orphaned and adopted separately from pending callbacks, but counts
* apply to all callbacks. Locking must be used to make sure that
* both orphaned-callbacks lists are consistent.)
*/
static inline void rcu_segcblist_extract_count(struct rcu_segcblist *rsclp,
struct rcu_cblist *rclp)
{
rclp->len_lazy += rsclp->len_lazy;
rclp->len += rsclp->len;
rsclp->len_lazy = 0;
WRITE_ONCE(rsclp->len, 0); /* ->len sampled locklessly. */
}
/*
* Extract only those callbacks ready to be invoked from the specified
* rcu_segcblist structure and place them in the specified rcu_cblist
* structure.
*/
static inline void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
struct rcu_cblist *rclp)
{
int i;
if (!rcu_segcblist_ready_cbs(rsclp))
return; /* Nothing to do. */
*rclp->tail = rsclp->head;
rsclp->head = *rsclp->tails[RCU_DONE_TAIL];
*rsclp->tails[RCU_DONE_TAIL] = NULL;
rclp->tail = rsclp->tails[RCU_DONE_TAIL];
for (i = RCU_CBLIST_NSEGS - 1; i >= RCU_DONE_TAIL; i--)
if (rsclp->tails[i] == rsclp->tails[RCU_DONE_TAIL])
rsclp->tails[i] = &rsclp->head;
}
/*
* Extract only those callbacks still pending (not yet ready to be
* invoked) from the specified rcu_segcblist structure and place them in
* the specified rcu_cblist structure. Note that this loses information
* about any callbacks that might have been partway done waiting for
* their grace period. Too bad! They will have to start over.
*/
static inline void
rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
struct rcu_cblist *rclp)
{
int i;
if (!rcu_segcblist_pend_cbs(rsclp))
return; /* Nothing to do. */
*rclp->tail = *rsclp->tails[RCU_DONE_TAIL];
rclp->tail = rsclp->tails[RCU_NEXT_TAIL];
*rsclp->tails[RCU_DONE_TAIL] = NULL;
for (i = RCU_DONE_TAIL + 1; i < RCU_CBLIST_NSEGS; i++)
rsclp->tails[i] = rsclp->tails[RCU_DONE_TAIL];
}
/*
* Move the entire contents of the specified rcu_segcblist structure,
* counts, callbacks, and all, to the specified rcu_cblist structure.
* @@@ Why do we need this??? Moving early-boot CBs to NOCB lists?
* @@@ Memory barrier needed? (Not if only used at boot time...)
*/
static inline void rcu_segcblist_extract_all(struct rcu_segcblist *rsclp,
struct rcu_cblist *rclp)
{
rcu_segcblist_extract_done_cbs(rsclp, rclp);
rcu_segcblist_extract_pend_cbs(rsclp, rclp);
rcu_segcblist_extract_count(rsclp, rclp);
}
/*
* Insert counts from the specified rcu_cblist structure in the
* specified rcu_segcblist structure.
*/
static inline void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
struct rcu_cblist *rclp)
{
rsclp->len_lazy += rclp->len_lazy;
/* ->len sampled locklessly. */
WRITE_ONCE(rsclp->len, rsclp->len + rclp->len);
rclp->len_lazy = 0;
rclp->len = 0;
}
/*
* Move callbacks from the specified rcu_cblist to the beginning of the
* done-callbacks segment of the specified rcu_segcblist.
*/
static inline void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
struct rcu_cblist *rclp)
{
int i;
if (!rclp->head)
return; /* No callbacks to move. */
*rclp->tail = rsclp->head;
rsclp->head = rclp->head;
for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++)
if (&rsclp->head == rsclp->tails[i])
rsclp->tails[i] = rclp->tail;
else
break;
rclp->head = NULL;
rclp->tail = &rclp->head;
}
/*
* Move callbacks from the specified rcu_cblist to the end of the
* new-callbacks segment of the specified rcu_segcblist.
*/
static inline void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
struct rcu_cblist *rclp)
{
if (!rclp->head)
return; /* Nothing to do. */
*rsclp->tails[RCU_NEXT_TAIL] = rclp->head;
rsclp->tails[RCU_NEXT_TAIL] = rclp->tail;
rclp->head = NULL;
rclp->tail = &rclp->head;
}
/*
* Advance the callbacks in the specified rcu_segcblist structure based
* on the current value passed in for the grace-period counter.
*/
static inline void rcu_segcblist_advance(struct rcu_segcblist *rsclp,
unsigned long seq)
{
int i, j;
WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp));
if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL))
return;
/*
* Find all callbacks whose ->gp_seq numbers indicate that they
* are ready to invoke, and put them into the RCU_DONE_TAIL segment.
*/
for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) {
if (ULONG_CMP_LT(seq, rsclp->gp_seq[i]))
break;
rsclp->tails[RCU_DONE_TAIL] = rsclp->tails[i];
}
/* If no callbacks moved, nothing more need be done. */
if (i == RCU_WAIT_TAIL)
return;
/* Clean up tail pointers that might have been misordered above. */
for (j = RCU_WAIT_TAIL; j < i; j++)
rsclp->tails[j] = rsclp->tails[RCU_DONE_TAIL];
/*
* Callbacks moved, so clean up the misordered ->tails[] pointers
* that now point into the middle of the list of ready-to-invoke
* callbacks. The overall effect is to copy down the later pointers
* into the gap that was created by the now-ready segments.
*/
for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
if (rsclp->tails[j] == rsclp->tails[RCU_NEXT_TAIL])
break; /* No more callbacks. */
rsclp->tails[j] = rsclp->tails[i];
rsclp->gp_seq[j] = rsclp->gp_seq[i];
}
}
/*
* "Accelerate" callbacks based on more-accurate grace-period information.
* The reason for this is that RCU does not synchronize the beginnings and
* ends of grace periods, and that callbacks are posted locally. This in
* turn means that the callbacks must be labelled conservatively early
* on, as getting exact information would degrade both performance and
* scalability. When more accurate grace-period information becomes
* available, previously posted callbacks can be "accelerated", marking
* them to complete at the end of the earlier grace period.
*
* This function operates on an rcu_segcblist structure, and also the
* grace-period sequence number seq at which new callbacks would become
* ready to invoke. Returns true if there are callbacks that won't be
* ready to invoke until seq, false otherwise.
*/
static inline bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp,
unsigned long seq)
{
int i;
WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp));
if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL))
return false;
/*
* Find the segment preceding the oldest segment of callbacks
* whose ->gp_seq[] completion is at or after that passed in via
* "seq", skipping any empty segments. This oldest segment, along
* with any later segments, can be merged in with any newly arrived
* callbacks in the RCU_NEXT_TAIL segment, and assigned "seq"
* as their ->gp_seq[] grace-period completion sequence number.
*/
for (i = RCU_NEXT_READY_TAIL; i > RCU_DONE_TAIL; i--)
if (rsclp->tails[i] != rsclp->tails[i - 1] &&
ULONG_CMP_LT(rsclp->gp_seq[i], seq))
break;
/*
* If all the segments contain callbacks that correspond to
* earlier grace-period sequence numbers than "seq", leave.
* Assuming that the rcu_segcblist structure has enough
* segments in its arrays, this can only happen if some of
* the non-done segments contain callbacks that really are
* ready to invoke. This situation will get straightened
* out by the next call to rcu_segcblist_advance().
*
* Also advance to the oldest segment of callbacks whose
* ->gp_seq[] completion is at or after that passed in via "seq",
* skipping any empty segments.
*/
if (++i >= RCU_NEXT_TAIL)
return false;
/*
* Merge all later callbacks, including newly arrived callbacks,
* into the segment located by the for-loop above. Assign "seq"
* as the ->gp_seq[] value in order to correctly handle the case
* where there were no pending callbacks in the rcu_segcblist
* structure other than in the RCU_NEXT_TAIL segment.
*/
for (; i < RCU_NEXT_TAIL; i++) {
rsclp->tails[i] = rsclp->tails[RCU_NEXT_TAIL];
rsclp->gp_seq[i] = seq;
}
return true;
}
/*
* Scan the specified rcu_segcblist structure for callbacks that need
* a grace period later than the one specified by "seq". We don't look
* at the RCU_DONE_TAIL or RCU_NEXT_TAIL segments because they don't
* have a grace-period sequence number.
*/
static inline bool rcu_segcblist_future_gp_needed(struct rcu_segcblist *rsclp,
unsigned long seq)
{
int i;
for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++)
if (rsclp->tails[i - 1] != rsclp->tails[i] &&
ULONG_CMP_LT(seq, rsclp->gp_seq[i]))
return true;
return false;
}
/*
* Interim function to return rcu_segcblist head pointer. Longer term, the
* rcu_segcblist will be used more pervasively, removing the need for this
* function.
*/
static inline struct rcu_head *rcu_segcblist_head(struct rcu_segcblist *rsclp)
{
return rsclp->head;
}
/*
* Interim function to return rcu_segcblist head pointer. Longer term, the
* rcu_segcblist will be used more pervasively, removing the need for this
* function.
*/
static inline struct rcu_head **rcu_segcblist_tail(struct rcu_segcblist *rsclp)
{
WARN_ON_ONCE(rcu_segcblist_empty(rsclp));
return rsclp->tails[RCU_NEXT_TAIL];
}
#endif /* __KERNEL_RCU_SEGCBLIST_H */

3
include/linux/rculist.h
View File

@@ -509,7 +509,8 @@ static inline void hlist_add_tail_rcu(struct hlist_node *n,
{
struct hlist_node *i, *last = NULL;
for (i = hlist_first_rcu(h); i; i = hlist_next_rcu(i))
/* Note: write side code, so rcu accessors are not needed. */
for (i = h->first; i; i = i->next)
last = i;
if (last) {

17
include/linux/rcupdate.h
View File

@@ -363,15 +363,20 @@ static inline void rcu_init_nohz(void)
#ifdef CONFIG_TASKS_RCU
#define TASKS_RCU(x) x
extern struct srcu_struct tasks_rcu_exit_srcu;
#define rcu_note_voluntary_context_switch(t) \
#define rcu_note_voluntary_context_switch_lite(t) \
do { \
rcu_all_qs(); \
if (READ_ONCE((t)->rcu_tasks_holdout)) \
WRITE_ONCE((t)->rcu_tasks_holdout, false); \
} while (0)
#define rcu_note_voluntary_context_switch(t) \
do { \
rcu_all_qs(); \
rcu_note_voluntary_context_switch_lite(t); \
} while (0)
#else /* #ifdef CONFIG_TASKS_RCU */
#define TASKS_RCU(x) do { } while (0)
#define rcu_note_voluntary_context_switch(t) rcu_all_qs()
#define rcu_note_voluntary_context_switch_lite(t) do { } while (0)
#define rcu_note_voluntary_context_switch(t) rcu_all_qs()
#endif /* #else #ifdef CONFIG_TASKS_RCU */
/**
@@ -1127,11 +1132,11 @@ do { \
* if the UNLOCK and LOCK are executed by the same CPU or if the
* UNLOCK and LOCK operate on the same lock variable.
*/
#ifdef CONFIG_PPC
#ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE
#define smp_mb__after_unlock_lock() smp_mb() /* Full ordering for lock. */
#else /* #ifdef CONFIG_PPC */
#else /* #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */
#define smp_mb__after_unlock_lock() do { } while (0)
#endif /* #else #ifdef CONFIG_PPC */
#endif /* #else #ifdef CONFIG_ARCH_WEAK_RELEASE_ACQUIRE */
#endif /* __LINUX_RCUPDATE_H */

24
include/linux/rcutiny.h
View File

@@ -33,6 +33,11 @@ static inline int rcu_dynticks_snap(struct rcu_dynticks *rdtp)
return 0;
}
static inline bool rcu_eqs_special_set(int cpu)
{
return false; /* Never flag non-existent other CPUs! */
}
static inline unsigned long get_state_synchronize_rcu(void)
{
return 0;
@@ -87,10 +92,11 @@ static inline void kfree_call_rcu(struct rcu_head *head,
call_rcu(head, func);
}
static inline void rcu_note_context_switch(void)
{
rcu_sched_qs();
}
#define rcu_note_context_switch(preempt) \
do { \
rcu_sched_qs(); \
rcu_note_voluntary_context_switch_lite(current); \
} while (0)
/*
* Take advantage of the fact that there is only one CPU, which
@@ -212,14 +218,14 @@ static inline void exit_rcu(void)
{
}
#ifdef CONFIG_DEBUG_LOCK_ALLOC
#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SRCU)
extern int rcu_scheduler_active __read_mostly;
void rcu_scheduler_starting(void);
#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
#else /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SRCU) */
static inline void rcu_scheduler_starting(void)
{
}
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
#endif /* #else #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SRCU) */
#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE)
@@ -237,6 +243,10 @@ static inline bool rcu_is_watching(void)
#endif /* #else defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
static inline void rcu_request_urgent_qs_task(struct task_struct *t)
{
}
static inline void rcu_all_qs(void)
{
barrier(); /* Avoid RCU read-side critical sections leaking across. */

5
include/linux/rcutree.h
View File

@@ -30,7 +30,7 @@
#ifndef __LINUX_RCUTREE_H
#define __LINUX_RCUTREE_H
void rcu_note_context_switch(void);
void rcu_note_context_switch(bool preempt);
int rcu_needs_cpu(u64 basem, u64 *nextevt);
void rcu_cpu_stall_reset(void);
@@ -41,7 +41,7 @@ void rcu_cpu_stall_reset(void);
*/
static inline void rcu_virt_note_context_switch(int cpu)
{
rcu_note_context_switch();
rcu_note_context_switch(false);
}
void synchronize_rcu_bh(void);
@@ -108,6 +108,7 @@ void rcu_scheduler_starting(void);
extern int rcu_scheduler_active __read_mostly;
bool rcu_is_watching(void);
void rcu_request_urgent_qs_task(struct task_struct *t);
void rcu_all_qs(void);

6
include/linux/slab.h
View File

@@ -28,7 +28,7 @@
#define SLAB_STORE_USER 0x00010000UL /* DEBUG: Store the last owner for bug hunting */
#define SLAB_PANIC 0x00040000UL /* Panic if kmem_cache_create() fails */
/*
* SLAB_DESTROY_BY_RCU - **WARNING** READ THIS!
* SLAB_TYPESAFE_BY_RCU - **WARNING** READ THIS!
*
* This delays freeing the SLAB page by a grace period, it does _NOT_
* delay object freeing. This means that if you do kmem_cache_free()
@@ -61,8 +61,10 @@
*
* rcu_read_lock before reading the address, then rcu_read_unlock after
* taking the spinlock within the structure expected at that address.
*
* Note that SLAB_TYPESAFE_BY_RCU was originally named SLAB_DESTROY_BY_RCU.
*/
#define SLAB_DESTROY_BY_RCU 0x00080000UL /* Defer freeing slabs to RCU */
#define SLAB_TYPESAFE_BY_RCU 0x00080000UL /* Defer freeing slabs to RCU */
#define SLAB_MEM_SPREAD 0x00100000UL /* Spread some memory over cpuset */
#define SLAB_TRACE 0x00200000UL /* Trace allocations and frees */

84
include/linux/srcu.h
View File

@@ -22,7 +22,7 @@
* Lai Jiangshan <laijs@cn.fujitsu.com>
*
* For detailed explanation of Read-Copy Update mechanism see -
* Documentation/RCU/ *.txt
* Documentation/RCU/ *.txt
*
*/
@@ -32,35 +32,9 @@
#include <linux/mutex.h>
#include <linux/rcupdate.h>
#include <linux/workqueue.h>
#include <linux/rcu_segcblist.h>
struct srcu_array {
unsigned long lock_count[2];
unsigned long unlock_count[2];
};
struct rcu_batch {
struct rcu_head *head, **tail;
};
#define RCU_BATCH_INIT(name) { NULL, &(name.head) }
struct srcu_struct {
unsigned long completed;
struct srcu_array __percpu *per_cpu_ref;
spinlock_t queue_lock; /* protect ->batch_queue, ->running */
bool running;
/* callbacks just queued */
struct rcu_batch batch_queue;
/* callbacks try to do the first check_zero */
struct rcu_batch batch_check0;
/* callbacks done with the first check_zero and the flip */
struct rcu_batch batch_check1;
struct rcu_batch batch_done;
struct delayed_work work;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
};
struct srcu_struct;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -82,46 +56,15 @@ int init_srcu_struct(struct srcu_struct *sp);
#define __SRCU_DEP_MAP_INIT(srcu_name)
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
void process_srcu(struct work_struct *work);
#define __SRCU_STRUCT_INIT(name) \
{ \
.completed = -300, \
.per_cpu_ref = &name##_srcu_array, \
.queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \
.running = false, \
.batch_queue = RCU_BATCH_INIT(name.batch_queue), \
.batch_check0 = RCU_BATCH_INIT(name.batch_check0), \
.batch_check1 = RCU_BATCH_INIT(name.batch_check1), \
.batch_done = RCU_BATCH_INIT(name.batch_done), \
.work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
__SRCU_DEP_MAP_INIT(name) \
}
/*
* Define and initialize a srcu struct at build time.
* Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
*
* Note that although DEFINE_STATIC_SRCU() hides the name from other
* files, the per-CPU variable rules nevertheless require that the
* chosen name be globally unique. These rules also prohibit use of
* DEFINE_STATIC_SRCU() within a function. If these rules are too
* restrictive, declare the srcu_struct manually. For example, in
* each file:
*
* static struct srcu_struct my_srcu;
*
* Then, before the first use of each my_srcu, manually initialize it:
*
* init_srcu_struct(&my_srcu);
*
* See include/linux/percpu-defs.h for the rules on per-CPU variables.
*/
#define __DEFINE_SRCU(name, is_static) \
static DEFINE_PER_CPU(struct srcu_array, name##_srcu_array);\
is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
#ifdef CONFIG_TINY_SRCU
#include <linux/srcutiny.h>
#elif defined(CONFIG_TREE_SRCU)
#include <linux/srcutree.h>
#elif defined(CONFIG_CLASSIC_SRCU)
#include <linux/srcuclassic.h>
#else
#error "Unknown SRCU implementation specified to kernel configuration"
#endif
/**
* call_srcu() - Queue a callback for invocation after an SRCU grace period
@@ -147,9 +90,6 @@ void cleanup_srcu_struct(struct srcu_struct *sp);
int __srcu_read_lock(struct srcu_struct *sp) __acquires(sp);
void __srcu_read_unlock(struct srcu_struct *sp, int idx) __releases(sp);
void synchronize_srcu(struct srcu_struct *sp);
void synchronize_srcu_expedited(struct srcu_struct *sp);
unsigned long srcu_batches_completed(struct srcu_struct *sp);
void srcu_barrier(struct srcu_struct *sp);
#ifdef CONFIG_DEBUG_LOCK_ALLOC

101
include/linux/srcuclassic.h Normal file
View File

@@ -0,0 +1,101 @@
/*
* Sleepable Read-Copy Update mechanism for mutual exclusion,
* classic v4.11 variant.
*
* 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) IBM Corporation, 2017
*
* Author: Paul McKenney <paulmck@us.ibm.com>
*/
#ifndef _LINUX_SRCU_CLASSIC_H
#define _LINUX_SRCU_CLASSIC_H
struct srcu_array {
unsigned long lock_count[2];
unsigned long unlock_count[2];
};
struct rcu_batch {
struct rcu_head *head, **tail;
};
#define RCU_BATCH_INIT(name) { NULL, &(name.head) }
struct srcu_struct {
unsigned long completed;
struct srcu_array __percpu *per_cpu_ref;
spinlock_t queue_lock; /* protect ->batch_queue, ->running */
bool running;
/* callbacks just queued */
struct rcu_batch batch_queue;
/* callbacks try to do the first check_zero */
struct rcu_batch batch_check0;
/* callbacks done with the first check_zero and the flip */
struct rcu_batch batch_check1;
struct rcu_batch batch_done;
struct delayed_work work;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
};
void process_srcu(struct work_struct *work);
#define __SRCU_STRUCT_INIT(name) \
{ \
.completed = -300, \
.per_cpu_ref = &name##_srcu_array, \
.queue_lock = __SPIN_LOCK_UNLOCKED(name.queue_lock), \
.running = false, \
.batch_queue = RCU_BATCH_INIT(name.batch_queue), \
.batch_check0 = RCU_BATCH_INIT(name.batch_check0), \
.batch_check1 = RCU_BATCH_INIT(name.batch_check1), \
.batch_done = RCU_BATCH_INIT(name.batch_done), \
.work = __DELAYED_WORK_INITIALIZER(name.work, process_srcu, 0),\
__SRCU_DEP_MAP_INIT(name) \
}
/*
* Define and initialize a srcu struct at build time.
* Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
*
* Note that although DEFINE_STATIC_SRCU() hides the name from other
* files, the per-CPU variable rules nevertheless require that the
* chosen name be globally unique. These rules also prohibit use of
* DEFINE_STATIC_SRCU() within a function. If these rules are too
* restrictive, declare the srcu_struct manually. For example, in
* each file:
*
* static struct srcu_struct my_srcu;
*
* Then, before the first use of each my_srcu, manually initialize it:
*
* init_srcu_struct(&my_srcu);
*
* See include/linux/percpu-defs.h for the rules on per-CPU variables.
*/
#define __DEFINE_SRCU(name, is_static) \
static DEFINE_PER_CPU(struct srcu_array, name##_srcu_array);\
is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
void synchronize_srcu_expedited(struct srcu_struct *sp);
void srcu_barrier(struct srcu_struct *sp);
unsigned long srcu_batches_completed(struct srcu_struct *sp);
#endif

81
include/linux/srcutiny.h Normal file
View File

@@ -0,0 +1,81 @@
/*
* Sleepable Read-Copy Update mechanism for mutual exclusion,
* tiny variant.
*
* 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) IBM Corporation, 2017
*
* Author: Paul McKenney <paulmck@us.ibm.com>
*/
#ifndef _LINUX_SRCU_TINY_H
#define _LINUX_SRCU_TINY_H
#include <linux/swait.h>
struct srcu_struct {
int srcu_lock_nesting[2]; /* srcu_read_lock() nesting depth. */
struct swait_queue_head srcu_wq;
/* Last srcu_read_unlock() wakes GP. */
unsigned long srcu_gp_seq; /* GP seq # for callback tagging. */
struct rcu_segcblist srcu_cblist;
/* Pending SRCU callbacks. */
int srcu_idx; /* Current reader array element. */
bool srcu_gp_running; /* GP workqueue running? */
bool srcu_gp_waiting; /* GP waiting for readers? */
struct work_struct srcu_work; /* For driving grace periods. */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
};
void srcu_drive_gp(struct work_struct *wp);
#define __SRCU_STRUCT_INIT(name) \
{ \
.srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq), \
.srcu_cblist = RCU_SEGCBLIST_INITIALIZER(name.srcu_cblist), \
.srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp), \
__SRCU_DEP_MAP_INIT(name) \
}
/*
* This odd _STATIC_ arrangement is needed for API compatibility with
* Tree SRCU, which needs some per-CPU data.
*/
#define DEFINE_SRCU(name) \
struct srcu_struct name = __SRCU_STRUCT_INIT(name)
#define DEFINE_STATIC_SRCU(name) \
static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
void synchronize_srcu(struct srcu_struct *sp);
static inline void synchronize_srcu_expedited(struct srcu_struct *sp)
{
synchronize_srcu(sp);
}
static inline void srcu_barrier(struct srcu_struct *sp)
{
synchronize_srcu(sp);
}
static inline unsigned long srcu_batches_completed(struct srcu_struct *sp)
{
return 0;
}
#endif

139
include/linux/srcutree.h Normal file
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@@ -0,0 +1,139 @@
/*
* Sleepable Read-Copy Update mechanism for mutual exclusion,
* tree variant.
*
* 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) IBM Corporation, 2017
*
* Author: Paul McKenney <paulmck@us.ibm.com>
*/
#ifndef _LINUX_SRCU_TREE_H
#define _LINUX_SRCU_TREE_H
#include <linux/rcu_node_tree.h>
#include <linux/completion.h>
struct srcu_node;
struct srcu_struct;
/*
* Per-CPU structure feeding into leaf srcu_node, similar in function
* to rcu_node.
*/
struct srcu_data {
/* Read-side state. */
unsigned long srcu_lock_count[2]; /* Locks per CPU. */
unsigned long srcu_unlock_count[2]; /* Unlocks per CPU. */
/* Update-side state. */
spinlock_t lock ____cacheline_internodealigned_in_smp;
struct rcu_segcblist srcu_cblist; /* List of callbacks.*/
unsigned long srcu_gp_seq_needed; /* Furthest future GP needed. */
bool srcu_cblist_invoking; /* Invoking these CBs? */
struct delayed_work work; /* Context for CB invoking. */
struct rcu_head srcu_barrier_head; /* For srcu_barrier() use. */
struct srcu_node *mynode; /* Leaf srcu_node. */
int cpu;
struct srcu_struct *sp;
};
/*
* Node in SRCU combining tree, similar in function to rcu_data.
*/
struct srcu_node {
spinlock_t lock;
unsigned long srcu_have_cbs[4]; /* GP seq for children */
/* having CBs, but only */
/* is > ->srcu_gq_seq. */
struct srcu_node *srcu_parent; /* Next up in tree. */
int grplo; /* Least CPU for node. */
int grphi; /* Biggest CPU for node. */
};
/*
* Per-SRCU-domain structure, similar in function to rcu_state.
*/
struct srcu_struct {
struct srcu_node node[NUM_RCU_NODES]; /* Combining tree. */
struct srcu_node *level[RCU_NUM_LVLS + 1];
/* First node at each level. */
struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
spinlock_t gp_lock; /* protect ->srcu_cblist */
struct mutex srcu_gp_mutex; /* Serialize GP work. */
unsigned int srcu_idx; /* Current rdr array element. */
unsigned long srcu_gp_seq; /* Grace-period seq #. */
unsigned long srcu_gp_seq_needed; /* Latest gp_seq needed. */
atomic_t srcu_exp_cnt; /* # ongoing expedited GPs. */
struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
struct mutex srcu_barrier_mutex; /* Serialize barrier ops. */
struct completion srcu_barrier_completion;
/* Awaken barrier rq at end. */
atomic_t srcu_barrier_cpu_cnt; /* # CPUs not yet posting a */
/* callback for the barrier */
/* operation. */
struct delayed_work work;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
};
/* Values for state variable (bottom bits of ->srcu_gp_seq). */
#define SRCU_STATE_IDLE 0
#define SRCU_STATE_SCAN1 1
#define SRCU_STATE_SCAN2 2
void process_srcu(struct work_struct *work);
#define __SRCU_STRUCT_INIT(name) \
{ \
.sda = &name##_srcu_data, \
.gp_lock = __SPIN_LOCK_UNLOCKED(name.gp_lock), \
.srcu_gp_seq_needed = 0 - 1, \
__SRCU_DEP_MAP_INIT(name) \
}
/*
* Define and initialize a srcu struct at build time.
* Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
*
* Note that although DEFINE_STATIC_SRCU() hides the name from other
* files, the per-CPU variable rules nevertheless require that the
* chosen name be globally unique. These rules also prohibit use of
* DEFINE_STATIC_SRCU() within a function. If these rules are too
* restrictive, declare the srcu_struct manually. For example, in
* each file:
*
* static struct srcu_struct my_srcu;
*
* Then, before the first use of each my_srcu, manually initialize it:
*
* init_srcu_struct(&my_srcu);
*
* See include/linux/percpu-defs.h for the rules on per-CPU variables.
*/
#define __DEFINE_SRCU(name, is_static) \
static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);\
is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name)
#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
void synchronize_srcu_expedited(struct srcu_struct *sp);
void srcu_barrier(struct srcu_struct *sp);
unsigned long srcu_batches_completed(struct srcu_struct *sp);
#endif

2
include/linux/types.h
View File

@@ -209,7 +209,7 @@ struct ustat {
* naturally due ABI requirements, but some architectures (like CRIS) have
* weird ABI and we need to ask it explicitly.
*
* The alignment is required to guarantee that bits 0 and 1 of @next will be
* The alignment is required to guarantee that bit 0 of @next will be
* clear under normal conditions -- as long as we use call_rcu(),
* call_rcu_bh(), call_rcu_sched(), or call_srcu() to queue callback.
*