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authorThomas Gleixner <tglx@linutronix.de>2007-10-11 05:17:24 -0400
committerThomas Gleixner <tglx@linutronix.de>2007-10-11 05:17:24 -0400
commit250c22777fe1ccd7ac588579a6c16db4c0161cc5 (patch)
tree55c317efb7d792ec6fdae1d1937c67a502c48dec /arch/x86_64/kernel/tsc_sync.c
parent2db55d344e529492545cb3b755c7e9ba8e4fa94e (diff)
x86_64: move kernel
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86_64/kernel/tsc_sync.c')
-rw-r--r--arch/x86_64/kernel/tsc_sync.c187
1 files changed, 0 insertions, 187 deletions
diff --git a/arch/x86_64/kernel/tsc_sync.c b/arch/x86_64/kernel/tsc_sync.c
deleted file mode 100644
index 355f5f506c81..000000000000
--- a/arch/x86_64/kernel/tsc_sync.c
+++ /dev/null
@@ -1,187 +0,0 @@
1/*
2 * arch/x86_64/kernel/tsc_sync.c: check TSC synchronization.
3 *
4 * Copyright (C) 2006, Red Hat, Inc., Ingo Molnar
5 *
6 * We check whether all boot CPUs have their TSC's synchronized,
7 * print a warning if not and turn off the TSC clock-source.
8 *
9 * The warp-check is point-to-point between two CPUs, the CPU
10 * initiating the bootup is the 'source CPU', the freshly booting
11 * CPU is the 'target CPU'.
12 *
13 * Only two CPUs may participate - they can enter in any order.
14 * ( The serial nature of the boot logic and the CPU hotplug lock
15 * protects against more than 2 CPUs entering this code. )
16 */
17#include <linux/spinlock.h>
18#include <linux/kernel.h>
19#include <linux/init.h>
20#include <linux/smp.h>
21#include <linux/nmi.h>
22#include <asm/tsc.h>
23
24/*
25 * Entry/exit counters that make sure that both CPUs
26 * run the measurement code at once:
27 */
28static __cpuinitdata atomic_t start_count;
29static __cpuinitdata atomic_t stop_count;
30
31/*
32 * We use a raw spinlock in this exceptional case, because
33 * we want to have the fastest, inlined, non-debug version
34 * of a critical section, to be able to prove TSC time-warps:
35 */
36static __cpuinitdata raw_spinlock_t sync_lock = __RAW_SPIN_LOCK_UNLOCKED;
37static __cpuinitdata cycles_t last_tsc;
38static __cpuinitdata cycles_t max_warp;
39static __cpuinitdata int nr_warps;
40
41/*
42 * TSC-warp measurement loop running on both CPUs:
43 */
44static __cpuinit void check_tsc_warp(void)
45{
46 cycles_t start, now, prev, end;
47 int i;
48
49 start = get_cycles_sync();
50 /*
51 * The measurement runs for 20 msecs:
52 */
53 end = start + tsc_khz * 20ULL;
54 now = start;
55
56 for (i = 0; ; i++) {
57 /*
58 * We take the global lock, measure TSC, save the
59 * previous TSC that was measured (possibly on
60 * another CPU) and update the previous TSC timestamp.
61 */
62 __raw_spin_lock(&sync_lock);
63 prev = last_tsc;
64 now = get_cycles_sync();
65 last_tsc = now;
66 __raw_spin_unlock(&sync_lock);
67
68 /*
69 * Be nice every now and then (and also check whether
70 * measurement is done [we also insert a 100 million
71 * loops safety exit, so we dont lock up in case the
72 * TSC readout is totally broken]):
73 */
74 if (unlikely(!(i & 7))) {
75 if (now > end || i > 100000000)
76 break;
77 cpu_relax();
78 touch_nmi_watchdog();
79 }
80 /*
81 * Outside the critical section we can now see whether
82 * we saw a time-warp of the TSC going backwards:
83 */
84 if (unlikely(prev > now)) {
85 __raw_spin_lock(&sync_lock);
86 max_warp = max(max_warp, prev - now);
87 nr_warps++;
88 __raw_spin_unlock(&sync_lock);
89 }
90
91 }
92}
93
94/*
95 * Source CPU calls into this - it waits for the freshly booted
96 * target CPU to arrive and then starts the measurement:
97 */
98void __cpuinit check_tsc_sync_source(int cpu)
99{
100 int cpus = 2;
101
102 /*
103 * No need to check if we already know that the TSC is not
104 * synchronized:
105 */
106 if (unsynchronized_tsc())
107 return;
108
109 printk(KERN_INFO "checking TSC synchronization [CPU#%d -> CPU#%d]:",
110 smp_processor_id(), cpu);
111
112 /*
113 * Reset it - in case this is a second bootup:
114 */
115 atomic_set(&stop_count, 0);
116
117 /*
118 * Wait for the target to arrive:
119 */
120 while (atomic_read(&start_count) != cpus-1)
121 cpu_relax();
122 /*
123 * Trigger the target to continue into the measurement too:
124 */
125 atomic_inc(&start_count);
126
127 check_tsc_warp();
128
129 while (atomic_read(&stop_count) != cpus-1)
130 cpu_relax();
131
132 /*
133 * Reset it - just in case we boot another CPU later:
134 */
135 atomic_set(&start_count, 0);
136
137 if (nr_warps) {
138 printk("\n");
139 printk(KERN_WARNING "Measured %Ld cycles TSC warp between CPUs,"
140 " turning off TSC clock.\n", max_warp);
141 mark_tsc_unstable("check_tsc_sync_source failed");
142 nr_warps = 0;
143 max_warp = 0;
144 last_tsc = 0;
145 } else {
146 printk(" passed.\n");
147 }
148
149 /*
150 * Let the target continue with the bootup:
151 */
152 atomic_inc(&stop_count);
153}
154
155/*
156 * Freshly booted CPUs call into this:
157 */
158void __cpuinit check_tsc_sync_target(void)
159{
160 int cpus = 2;
161
162 if (unsynchronized_tsc())
163 return;
164
165 /*
166 * Register this CPU's participation and wait for the
167 * source CPU to start the measurement:
168 */
169 atomic_inc(&start_count);
170 while (atomic_read(&start_count) != cpus)
171 cpu_relax();
172
173 check_tsc_warp();
174
175 /*
176 * Ok, we are done:
177 */
178 atomic_inc(&stop_count);
179
180 /*
181 * Wait for the source CPU to print stuff:
182 */
183 while (atomic_read(&stop_count) != cpus)
184 cpu_relax();
185}
186#undef NR_LOOPS
187
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