source: mainline/kernel/generic/include/cpu.h@ b2ec5cf

ticket/834-toolchain-update topic/msim-upgrade topic/simplify-dev-export
Last change on this file since b2ec5cf was b2ec5cf, checked in by Jiří Zárevúcky <zarevucky.jiri@…>, 2 years ago

Implement atomic_time_stat_t for lockless timekeeping

We keep monotonically increasing temporal statistics in several places.
They are frequently written from the thread that owns them, and rarely
read from other threads in certain syscalls. This new code serves the
purpose of avoiding the need for synchronization on the writer side.
On 64b system, we can simply assume that 64b writes are indivisible,
and relaxed atomic read/writes simply serve to formally prevent C
undefined behavior from data races (they translate to regular memory
reads/writes in assembly).

On 32b systems, we use the same algorithm that's been used for userspace
clock access, using three fields and some memory barriers to maintain
consistency of reads when the upper half changes. Only readers always
synchronize though. For writers, barriers are avoided in the common case
when the upper half remains unchanged.

  • Property mode set to 100644
File size: 3.2 KB
Line 
1/*
2 * Copyright (c) 2001-2004 Jakub Jermar
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 *
9 * - Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * - Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * - The name of the author may not be used to endorse or promote products
15 * derived from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29/** @addtogroup kernel_generic
30 * @{
31 */
32/** @file
33 */
34
35#ifndef KERN_CPU_H_
36#define KERN_CPU_H_
37
38#include <mm/tlb.h>
39#include <synch/spinlock.h>
40#include <proc/scheduler.h>
41#include <arch/cpu.h>
42#include <arch/context.h>
43#include <adt/list.h>
44#include <arch.h>
45
46#define CPU CURRENT->cpu
47
48/** CPU structure.
49 *
50 * There is one structure like this for every processor.
51 */
52typedef struct cpu {
53 IRQ_SPINLOCK_DECLARE(lock);
54
55 tlb_shootdown_msg_t tlb_messages[TLB_MESSAGE_QUEUE_LEN];
56 size_t tlb_messages_count;
57
58 atomic_size_t nrdy;
59 runq_t rq[RQ_COUNT];
60
61 IRQ_SPINLOCK_DECLARE(timeoutlock);
62 list_t timeout_active_list;
63
64 /**
65 * When system clock loses a tick, it is
66 * recorded here so that clock() can react.
67 * This variable is CPU-local and can be
68 * only accessed when interrupts are
69 * disabled.
70 */
71 size_t missed_clock_ticks;
72
73 /** Can only be accessed by the CPU represented by this structure when interrupts are disabled. */
74 uint64_t current_clock_tick;
75 uint64_t preempt_deadline; /* < when should the currently running thread be preempted */
76 uint64_t relink_deadline;
77
78 /**
79 * Processor cycle accounting.
80 */
81 bool idle;
82 uint64_t last_cycle;
83 atomic_time_stat_t idle_cycles;
84 atomic_time_stat_t busy_cycles;
85
86 /**
87 * Processor ID assigned by kernel.
88 */
89 unsigned int id;
90
91 bool active;
92 volatile bool tlb_active;
93
94 uint16_t frequency_mhz;
95 uint32_t delay_loop_const;
96
97 cpu_arch_t arch;
98
99 struct thread *fpu_owner;
100
101 /**
102 * Stack used by scheduler when there is no running thread.
103 */
104 uint8_t *stack;
105} cpu_t;
106
107extern cpu_t *cpus;
108
109extern void cpu_init(void);
110extern void cpu_list(void);
111
112extern void cpu_arch_init(void);
113extern void cpu_identify(void);
114extern void cpu_print_report(cpu_t *);
115
116#endif
117
118/** @}
119 */
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