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authorPaul E. McKenney <paulmck@linux.vnet.ibm.com>2008-12-18 15:55:32 -0500
committerIngo Molnar <mingo@elte.hu>2008-12-18 15:56:04 -0500
commit64db4cfff99c04cd5f550357edcc8780f96b54a2 (patch)
tree4856e788d21f0e31ed78a22b70b4521f7237705e /include
parentd110ec3a1e1f522e2e9dfceb9c36d6590c26d2d4 (diff)
"Tree RCU": scalable classic RCU implementation
This patch fixes a long-standing performance bug in classic RCU that results in massive internal-to-RCU lock contention on systems with more than a few hundred CPUs. Although this patch creates a separate flavor of RCU for ease of review and patch maintenance, it is intended to replace classic RCU. This patch still handles stress better than does mainline, so I am still calling it ready for inclusion. This patch is against the -tip tree. Nevertheless, experience on an actual 1000+ CPU machine would still be most welcome. Most of the changes noted below were found while creating an rcutiny (which should permit ejecting the current rcuclassic) and while doing detailed line-by-line documentation. Updates from v9 (http://lkml.org/lkml/2008/12/2/334): o Fixes from remainder of line-by-line code walkthrough, including comment spelling, initialization, undesirable narrowing due to type conversion, removing redundant memory barriers, removing redundant local-variable initialization, and removing redundant local variables. I do not believe that any of these fixes address the CPU-hotplug issues that Andi Kleen was seeing, but please do give it a whirl in case the machine is smarter than I am. A writeup from the walkthrough may be found at the following URL, in case you are suffering from terminal insomnia or masochism: http://www.kernel.org/pub/linux/kernel/people/paulmck/tmp/rcutree-walkthrough.2008.12.16a.pdf o Made rcutree tracing use seq_file, as suggested some time ago by Lai Jiangshan. o Added a .csv variant of the rcudata debugfs trace file, to allow people having thousands of CPUs to drop the data into a spreadsheet. Tested with oocalc and gnumeric. Updated documentation to suit. Updates from v8 (http://lkml.org/lkml/2008/11/15/139): o Fix a theoretical race between grace-period initialization and force_quiescent_state() that could occur if more than three jiffies were required to carry out the grace-period initialization. Which it might, if you had enough CPUs. o Apply Ingo's printk-standardization patch. o Substitute local variables for repeated accesses to global variables. o Fix comment misspellings and redundant (but harmless) increments of ->n_rcu_pending (this latter after having explicitly added it). o Apply checkpatch fixes. Updates from v7 (http://lkml.org/lkml/2008/10/10/291): o Fixed a number of problems noted by Gautham Shenoy, including the cpu-stall-detection bug that he was having difficulty convincing me was real. ;-) o Changed cpu-stall detection to wait for ten seconds rather than three in order to reduce false positive, as suggested by Ingo Molnar. o Produced a design document (http://lwn.net/Articles/305782/). The act of writing this document uncovered a number of both theoretical and "here and now" bugs as noted below. o Fix dynticks_nesting accounting confusion, simplify WARN_ON() condition, fix kerneldoc comments, and add memory barriers in dynticks interface functions. o Add more data to tracing. o Remove unused "rcu_barrier" field from rcu_data structure. o Count calls to rcu_pending() from scheduling-clock interrupt to use as a surrogate timebase should jiffies stop counting. o Fix a theoretical race between force_quiescent_state() and grace-period initialization. Yes, initialization does have to go on for some jiffies for this race to occur, but given enough CPUs... Updates from v6 (http://lkml.org/lkml/2008/9/23/448): o Fix a number of checkpatch.pl complaints. o Apply review comments from Ingo Molnar and Lai Jiangshan on the stall-detection code. o Fix several bugs in !CONFIG_SMP builds. o Fix a misspelled config-parameter name so that RCU now announces at boot time if stall detection is configured. o Run tests on numerous combinations of configurations parameters, which after the fixes above, now build and run correctly. Updates from v5 (http://lkml.org/lkml/2008/9/15/92, bad subject line): o Fix a compiler error in the !CONFIG_FANOUT_EXACT case (blew a changeset some time ago, and finally got around to retesting this option). o Fix some tracing bugs in rcupreempt that caused incorrect totals to be printed. o I now test with a more brutal random-selection online/offline script (attached). Probably more brutal than it needs to be on the people reading it as well, but so it goes. o A number of optimizations and usability improvements: o Make rcu_pending() ignore the grace-period timeout when there is no grace period in progress. o Make force_quiescent_state() avoid going for a global lock in the case where there is no grace period in progress. o Rearrange struct fields to improve struct layout. o Make call_rcu() initiate a grace period if RCU was idle, rather than waiting for the next scheduling clock interrupt. o Invoke rcu_irq_enter() and rcu_irq_exit() only when idle, as suggested by Andi Kleen. I still don't completely trust this change, and might back it out. o Make CONFIG_RCU_TRACE be the single config variable manipulated for all forms of RCU, instead of the prior confusion. o Document tracing files and formats for both rcupreempt and rcutree. Updates from v4 for those missing v5 given its bad subject line: o Separated dynticks interface so that NMIs and irqs call separate functions, greatly simplifying it. In particular, this code no longer requires a proof of correctness. ;-) o Separated dynticks state out into its own per-CPU structure, avoiding the duplicated accounting. o The case where a dynticks-idle CPU runs an irq handler that invokes call_rcu() is now correctly handled, forcing that CPU out of dynticks-idle mode. o Review comments have been applied (thank you all!!!). For but one example, fixed the dynticks-ordering issue that Manfred pointed out, saving me much debugging. ;-) o Adjusted rcuclassic and rcupreempt to handle dynticks changes. Attached is an updated patch to Classic RCU that applies a hierarchy, greatly reducing the contention on the top-level lock for large machines. This passes 10-hour concurrent rcutorture and online-offline testing on 128-CPU ppc64 without dynticks enabled, and exposes some timekeeping bugs in presence of dynticks (exciting working on a system where "sleep 1" hangs until interrupted...), which were fixed in the 2.6.27 kernel. It is getting more reliable than mainline by some measures, so the next version will be against -tip for inclusion. See also Manfred Spraul's recent patches (or his earlier work from 2004 at http://marc.info/?l=linux-kernel&m=108546384711797&w=2). We will converge onto a common patch in the fullness of time, but are currently exploring different regions of the design space. That said, I have already gratefully stolen quite a few of Manfred's ideas. This patch provides CONFIG_RCU_FANOUT, which controls the bushiness of the RCU hierarchy. Defaults to 32 on 32-bit machines and 64 on 64-bit machines. If CONFIG_NR_CPUS is less than CONFIG_RCU_FANOUT, there is no hierarchy. By default, the RCU initialization code will adjust CONFIG_RCU_FANOUT to balance the hierarchy, so strongly NUMA architectures may choose to set CONFIG_RCU_FANOUT_EXACT to disable this balancing, allowing the hierarchy to be exactly aligned to the underlying hardware. Up to two levels of hierarchy are permitted (in addition to the root node), allowing up to 16,384 CPUs on 32-bit systems and up to 262,144 CPUs on 64-bit systems. I just know that I am going to regret saying this, but this seems more than sufficient for the foreseeable future. (Some architectures might wish to set CONFIG_RCU_FANOUT=4, which would limit such architectures to 64 CPUs. If this becomes a real problem, additional levels can be added, but I doubt that it will make a significant difference on real hardware.) In the common case, a given CPU will manipulate its private rcu_data structure and the rcu_node structure that it shares with its immediate neighbors. This can reduce both lock and memory contention by multiple orders of magnitude, which should eliminate the need for the strange manipulations that are reported to be required when running Linux on very large systems. Some shortcomings: o More bugs will probably surface as a result of an ongoing line-by-line code inspection. Patches will be provided as required. o There are probably hangs, rcutorture failures, &c. Seems quite stable on a 128-CPU machine, but that is kind of small compared to 4096 CPUs. However, seems to do better than mainline. Patches will be provided as required. o The memory footprint of this version is several KB larger than rcuclassic. A separate UP-only rcutiny patch will be provided, which will reduce the memory footprint significantly, even compared to the old rcuclassic. One such patch passes light testing, and has a memory footprint smaller even than rcuclassic. Initial reaction from various embedded guys was "it is not worth it", so am putting it aside. Credits: o Manfred Spraul for ideas, review comments, and bugs spotted, as well as some good friendly competition. ;-) o Josh Triplett, Ingo Molnar, Peter Zijlstra, Mathieu Desnoyers, Lai Jiangshan, Andi Kleen, Andy Whitcroft, and Andrew Morton for reviews and comments. o Thomas Gleixner for much-needed help with some timer issues (see patches below). o Jon M. Tollefson, Tim Pepper, Andrew Theurer, Jose R. Santos, Andy Whitcroft, Darrick Wong, Nishanth Aravamudan, Anton Blanchard, Dave Kleikamp, and Nathan Lynch for keeping machines alive despite my heavy abuse^Wtesting. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'include')
-rw-r--r--include/linux/hardirq.h14
-rw-r--r--include/linux/rcupdate.h10
-rw-r--r--include/linux/rcutree.h329
3 files changed, 344 insertions, 9 deletions
diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
index 181006cc94a0..9b70b9231693 100644
--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -118,13 +118,17 @@ static inline void account_system_vtime(struct task_struct *tsk)
118} 118}
119#endif 119#endif
120 120
121#if defined(CONFIG_PREEMPT_RCU) && defined(CONFIG_NO_HZ) 121#if defined(CONFIG_NO_HZ) && !defined(CONFIG_CLASSIC_RCU)
122extern void rcu_irq_enter(void); 122extern void rcu_irq_enter(void);
123extern void rcu_irq_exit(void); 123extern void rcu_irq_exit(void);
124extern void rcu_nmi_enter(void);
125extern void rcu_nmi_exit(void);
124#else 126#else
125# define rcu_irq_enter() do { } while (0) 127# define rcu_irq_enter() do { } while (0)
126# define rcu_irq_exit() do { } while (0) 128# define rcu_irq_exit() do { } while (0)
127#endif /* CONFIG_PREEMPT_RCU */ 129# define rcu_nmi_enter() do { } while (0)
130# define rcu_nmi_exit() do { } while (0)
131#endif /* #if defined(CONFIG_NO_HZ) && !defined(CONFIG_CLASSIC_RCU) */
128 132
129/* 133/*
130 * It is safe to do non-atomic ops on ->hardirq_context, 134 * It is safe to do non-atomic ops on ->hardirq_context,
@@ -134,7 +138,6 @@ extern void rcu_irq_exit(void);
134 */ 138 */
135#define __irq_enter() \ 139#define __irq_enter() \
136 do { \ 140 do { \
137 rcu_irq_enter(); \
138 account_system_vtime(current); \ 141 account_system_vtime(current); \
139 add_preempt_count(HARDIRQ_OFFSET); \ 142 add_preempt_count(HARDIRQ_OFFSET); \
140 trace_hardirq_enter(); \ 143 trace_hardirq_enter(); \
@@ -153,7 +156,6 @@ extern void irq_enter(void);
153 trace_hardirq_exit(); \ 156 trace_hardirq_exit(); \
154 account_system_vtime(current); \ 157 account_system_vtime(current); \
155 sub_preempt_count(HARDIRQ_OFFSET); \ 158 sub_preempt_count(HARDIRQ_OFFSET); \
156 rcu_irq_exit(); \
157 } while (0) 159 } while (0)
158 160
159/* 161/*
@@ -161,7 +163,7 @@ extern void irq_enter(void);
161 */ 163 */
162extern void irq_exit(void); 164extern void irq_exit(void);
163 165
164#define nmi_enter() do { lockdep_off(); __irq_enter(); } while (0) 166#define nmi_enter() do { lockdep_off(); rcu_nmi_enter(); __irq_enter(); } while (0)
165#define nmi_exit() do { __irq_exit(); lockdep_on(); } while (0) 167#define nmi_exit() do { __irq_exit(); rcu_nmi_exit(); lockdep_on(); } while (0)
166 168
167#endif /* LINUX_HARDIRQ_H */ 169#endif /* LINUX_HARDIRQ_H */
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 86f1f5e43e33..bfd289aff576 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -52,11 +52,15 @@ struct rcu_head {
52 void (*func)(struct rcu_head *head); 52 void (*func)(struct rcu_head *head);
53}; 53};
54 54
55#ifdef CONFIG_CLASSIC_RCU 55#if defined(CONFIG_CLASSIC_RCU)
56#include <linux/rcuclassic.h> 56#include <linux/rcuclassic.h>
57#else /* #ifdef CONFIG_CLASSIC_RCU */ 57#elif defined(CONFIG_TREE_RCU)
58#include <linux/rcutree.h>
59#elif defined(CONFIG_PREEMPT_RCU)
58#include <linux/rcupreempt.h> 60#include <linux/rcupreempt.h>
59#endif /* #else #ifdef CONFIG_CLASSIC_RCU */ 61#else
62#error "Unknown RCU implementation specified to kernel configuration"
63#endif /* #else #if defined(CONFIG_CLASSIC_RCU) */
60 64
61#define RCU_HEAD_INIT { .next = NULL, .func = NULL } 65#define RCU_HEAD_INIT { .next = NULL, .func = NULL }
62#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT 66#define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
new file mode 100644
index 000000000000..d4368b7975c3
--- /dev/null
+++ b/include/linux/rcutree.h
@@ -0,0 +1,329 @@
1/*
2 * Read-Copy Update mechanism for mutual exclusion (tree-based version)
3 *
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
17 *
18 * Copyright IBM Corporation, 2008
19 *
20 * Author: Dipankar Sarma <dipankar@in.ibm.com>
21 * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical algorithm
22 *
23 * Based on the original work by Paul McKenney <paulmck@us.ibm.com>
24 * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
25 *
26 * For detailed explanation of Read-Copy Update mechanism see -
27 * Documentation/RCU
28 */
29
30#ifndef __LINUX_RCUTREE_H
31#define __LINUX_RCUTREE_H
32
33#include <linux/cache.h>
34#include <linux/spinlock.h>
35#include <linux/threads.h>
36#include <linux/percpu.h>
37#include <linux/cpumask.h>
38#include <linux/seqlock.h>
39
40/*
41 * Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT.
42 * In theory, it should be possible to add more levels straightforwardly.
43 * In practice, this has not been tested, so there is probably some
44 * bug somewhere.
45 */
46#define MAX_RCU_LVLS 3
47#define RCU_FANOUT (CONFIG_RCU_FANOUT)
48#define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT)
49#define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT)
50
51#if NR_CPUS <= RCU_FANOUT
52# define NUM_RCU_LVLS 1
53# define NUM_RCU_LVL_0 1
54# define NUM_RCU_LVL_1 (NR_CPUS)
55# define NUM_RCU_LVL_2 0
56# define NUM_RCU_LVL_3 0
57#elif NR_CPUS <= RCU_FANOUT_SQ
58# define NUM_RCU_LVLS 2
59# define NUM_RCU_LVL_0 1
60# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT - 1) / RCU_FANOUT)
61# define NUM_RCU_LVL_2 (NR_CPUS)
62# define NUM_RCU_LVL_3 0
63#elif NR_CPUS <= RCU_FANOUT_CUBE
64# define NUM_RCU_LVLS 3
65# define NUM_RCU_LVL_0 1
66# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT_SQ - 1) / RCU_FANOUT_SQ)
67# define NUM_RCU_LVL_2 (((NR_CPUS) + (RCU_FANOUT) - 1) / (RCU_FANOUT))
68# define NUM_RCU_LVL_3 NR_CPUS
69#else
70# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
71#endif /* #if (NR_CPUS) <= RCU_FANOUT */
72
73#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3)
74#define NUM_RCU_NODES (RCU_SUM - NR_CPUS)
75
76/*
77 * Dynticks per-CPU state.
78 */
79struct rcu_dynticks {
80 int dynticks_nesting; /* Track nesting level, sort of. */
81 int dynticks; /* Even value for dynticks-idle, else odd. */
82 int dynticks_nmi; /* Even value for either dynticks-idle or */
83 /* not in nmi handler, else odd. So this */
84 /* remains even for nmi from irq handler. */
85};
86
87/*
88 * Definition for node within the RCU grace-period-detection hierarchy.
89 */
90struct rcu_node {
91 spinlock_t lock;
92 unsigned long qsmask; /* CPUs or groups that need to switch in */
93 /* order for current grace period to proceed.*/
94 unsigned long qsmaskinit;
95 /* Per-GP initialization for qsmask. */
96 unsigned long grpmask; /* Mask to apply to parent qsmask. */
97 int grplo; /* lowest-numbered CPU or group here. */
98 int grphi; /* highest-numbered CPU or group here. */
99 u8 grpnum; /* CPU/group number for next level up. */
100 u8 level; /* root is at level 0. */
101 struct rcu_node *parent;
102} ____cacheline_internodealigned_in_smp;
103
104/* Index values for nxttail array in struct rcu_data. */
105#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */
106#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */
107#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */
108#define RCU_NEXT_TAIL 3
109#define RCU_NEXT_SIZE 4
110
111/* Per-CPU data for read-copy update. */
112struct rcu_data {
113 /* 1) quiescent-state and grace-period handling : */
114 long completed; /* Track rsp->completed gp number */
115 /* in order to detect GP end. */
116 long gpnum; /* Highest gp number that this CPU */
117 /* is aware of having started. */
118 long passed_quiesc_completed;
119 /* Value of completed at time of qs. */
120 bool passed_quiesc; /* User-mode/idle loop etc. */
121 bool qs_pending; /* Core waits for quiesc state. */
122 bool beenonline; /* CPU online at least once. */
123 struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
124 unsigned long grpmask; /* Mask to apply to leaf qsmask. */
125
126 /* 2) batch handling */
127 /*
128 * If nxtlist is not NULL, it is partitioned as follows.
129 * Any of the partitions might be empty, in which case the
130 * pointer to that partition will be equal to the pointer for
131 * the following partition. When the list is empty, all of
132 * the nxttail elements point to nxtlist, which is NULL.
133 *
134 * [*nxttail[RCU_NEXT_READY_TAIL], NULL = *nxttail[RCU_NEXT_TAIL]):
135 * Entries that might have arrived after current GP ended
136 * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]):
137 * Entries known to have arrived before current GP ended
138 * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]):
139 * Entries that batch # <= ->completed - 1: waiting for current GP
140 * [nxtlist, *nxttail[RCU_DONE_TAIL]):
141 * Entries that batch # <= ->completed
142 * The grace period for these entries has completed, and
143 * the other grace-period-completed entries may be moved
144 * here temporarily in rcu_process_callbacks().
145 */
146 struct rcu_head *nxtlist;
147 struct rcu_head **nxttail[RCU_NEXT_SIZE];
148 long qlen; /* # of queued callbacks */
149 long blimit; /* Upper limit on a processed batch */
150
151#ifdef CONFIG_NO_HZ
152 /* 3) dynticks interface. */
153 struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */
154 int dynticks_snap; /* Per-GP tracking for dynticks. */
155 int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */
156#endif /* #ifdef CONFIG_NO_HZ */
157
158 /* 4) reasons this CPU needed to be kicked by force_quiescent_state */
159#ifdef CONFIG_NO_HZ
160 unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */
161#endif /* #ifdef CONFIG_NO_HZ */
162 unsigned long offline_fqs; /* Kicked due to being offline. */
163 unsigned long resched_ipi; /* Sent a resched IPI. */
164
165 /* 5) state to allow this CPU to force_quiescent_state on others */
166 long n_rcu_pending; /* rcu_pending() calls since boot. */
167 long n_rcu_pending_force_qs; /* when to force quiescent states. */
168
169 int cpu;
170};
171
172/* Values for signaled field in struct rcu_state. */
173#define RCU_GP_INIT 0 /* Grace period being initialized. */
174#define RCU_SAVE_DYNTICK 1 /* Need to scan dyntick state. */
175#define RCU_FORCE_QS 2 /* Need to force quiescent state. */
176#ifdef CONFIG_NO_HZ
177#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK
178#else /* #ifdef CONFIG_NO_HZ */
179#define RCU_SIGNAL_INIT RCU_FORCE_QS
180#endif /* #else #ifdef CONFIG_NO_HZ */
181
182#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */
183#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
184#define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */
185#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rsp->jiffies_stall */
186#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */
187 /* to take at least one */
188 /* scheduling clock irq */
189 /* before ratting on them. */
190
191#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
192
193/*
194 * RCU global state, including node hierarchy. This hierarchy is
195 * represented in "heap" form in a dense array. The root (first level)
196 * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second
197 * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]),
198 * and the third level in ->node[m+1] and following (->node[m+1] referenced
199 * by ->level[2]). The number of levels is determined by the number of
200 * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy"
201 * consisting of a single rcu_node.
202 */
203struct rcu_state {
204 struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */
205 struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */
206 u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */
207 u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */
208 struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */
209
210 /* The following fields are guarded by the root rcu_node's lock. */
211
212 u8 signaled ____cacheline_internodealigned_in_smp;
213 /* Force QS state. */
214 long gpnum; /* Current gp number. */
215 long completed; /* # of last completed gp. */
216 spinlock_t onofflock; /* exclude on/offline and */
217 /* starting new GP. */
218 spinlock_t fqslock; /* Only one task forcing */
219 /* quiescent states. */
220 unsigned long jiffies_force_qs; /* Time at which to invoke */
221 /* force_quiescent_state(). */
222 unsigned long n_force_qs; /* Number of calls to */
223 /* force_quiescent_state(). */
224 unsigned long n_force_qs_lh; /* ~Number of calls leaving */
225 /* due to lock unavailable. */
226 unsigned long n_force_qs_ngp; /* Number of calls leaving */
227 /* due to no GP active. */
228#ifdef CONFIG_RCU_CPU_STALL_DETECTOR
229 unsigned long gp_start; /* Time at which GP started, */
230 /* but in jiffies. */
231 unsigned long jiffies_stall; /* Time at which to check */
232 /* for CPU stalls. */
233#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */
234#ifdef CONFIG_NO_HZ
235 long dynticks_completed; /* Value of completed @ snap. */
236#endif /* #ifdef CONFIG_NO_HZ */
237};
238
239extern struct rcu_state rcu_state;
240DECLARE_PER_CPU(struct rcu_data, rcu_data);
241
242extern struct rcu_state rcu_bh_state;
243DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
244
245/*
246 * Increment the quiescent state counter.
247 * The counter is a bit degenerated: We do not need to know
248 * how many quiescent states passed, just if there was at least
249 * one since the start of the grace period. Thus just a flag.
250 */
251static inline void rcu_qsctr_inc(int cpu)
252{
253 struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
254 rdp->passed_quiesc = 1;
255 rdp->passed_quiesc_completed = rdp->completed;
256}
257static inline void rcu_bh_qsctr_inc(int cpu)
258{
259 struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
260 rdp->passed_quiesc = 1;
261 rdp->passed_quiesc_completed = rdp->completed;
262}
263
264extern int rcu_pending(int cpu);
265extern int rcu_needs_cpu(int cpu);
266
267#ifdef CONFIG_DEBUG_LOCK_ALLOC
268extern struct lockdep_map rcu_lock_map;
269# define rcu_read_acquire() \
270 lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_)
271# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_)
272#else
273# define rcu_read_acquire() do { } while (0)
274# define rcu_read_release() do { } while (0)
275#endif
276
277static inline void __rcu_read_lock(void)
278{
279 preempt_disable();
280 __acquire(RCU);
281 rcu_read_acquire();
282}
283static inline void __rcu_read_unlock(void)
284{
285 rcu_read_release();
286 __release(RCU);
287 preempt_enable();
288}
289static inline void __rcu_read_lock_bh(void)
290{
291 local_bh_disable();
292 __acquire(RCU_BH);
293 rcu_read_acquire();
294}
295static inline void __rcu_read_unlock_bh(void)
296{
297 rcu_read_release();
298 __release(RCU_BH);
299 local_bh_enable();
300}
301
302#define __synchronize_sched() synchronize_rcu()
303
304#define call_rcu_sched(head, func) call_rcu(head, func)
305
306static inline void rcu_init_sched(void)
307{
308}
309
310extern void __rcu_init(void);
311extern void rcu_check_callbacks(int cpu, int user);
312extern void rcu_restart_cpu(int cpu);
313
314extern long rcu_batches_completed(void);
315extern long rcu_batches_completed_bh(void);
316
317#ifdef CONFIG_NO_HZ
318void rcu_enter_nohz(void);
319void rcu_exit_nohz(void);
320#else /* CONFIG_NO_HZ */
321static inline void rcu_enter_nohz(void)
322{
323}
324static inline void rcu_exit_nohz(void)
325{
326}
327#endif /* CONFIG_NO_HZ */
328
329#endif /* __LINUX_RCUTREE_H */
generated by cgit v1.2.2 (git 2.25.0) at 2024-12-02 06:28:43 -0500