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Commit | Line | Data |
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d5de8841 JF |
1 | /* |
2 | * Split spinlock implementation out into its own file, so it can be | |
3 | * compiled in a FTRACE-compatible way. | |
4 | */ | |
5 | #include <linux/kernel_stat.h> | |
6 | #include <linux/spinlock.h> | |
994025ca JF |
7 | #include <linux/debugfs.h> |
8 | #include <linux/log2.h> | |
5a0e3ad6 | 9 | #include <linux/gfp.h> |
354e7b76 | 10 | #include <linux/slab.h> |
d5de8841 JF |
11 | |
12 | #include <asm/paravirt.h> | |
13 | ||
14 | #include <xen/interface/xen.h> | |
15 | #include <xen/events.h> | |
16 | ||
17 | #include "xen-ops.h" | |
994025ca JF |
18 | #include "debugfs.h" |
19 | ||
80bd58fe JF |
20 | enum xen_contention_stat { |
21 | TAKEN_SLOW, | |
22 | TAKEN_SLOW_PICKUP, | |
23 | TAKEN_SLOW_SPURIOUS, | |
24 | RELEASED_SLOW, | |
25 | RELEASED_SLOW_KICKED, | |
26 | NR_CONTENTION_STATS | |
27 | }; | |
994025ca | 28 | |
994025ca | 29 | |
80bd58fe | 30 | #ifdef CONFIG_XEN_DEBUG_FS |
f8eca41f | 31 | #define HISTO_BUCKETS 30 |
80bd58fe JF |
32 | static struct xen_spinlock_stats |
33 | { | |
34 | u32 contention_stats[NR_CONTENTION_STATS]; | |
f8eca41f | 35 | u32 histo_spin_blocked[HISTO_BUCKETS+1]; |
f8eca41f | 36 | u64 time_blocked; |
994025ca JF |
37 | } spinlock_stats; |
38 | ||
39 | static u8 zero_stats; | |
40 | ||
994025ca JF |
41 | static inline void check_zero(void) |
42 | { | |
80bd58fe JF |
43 | u8 ret; |
44 | u8 old = ACCESS_ONCE(zero_stats); | |
45 | if (unlikely(old)) { | |
46 | ret = cmpxchg(&zero_stats, old, 0); | |
47 | /* This ensures only one fellow resets the stat */ | |
48 | if (ret == old) | |
49 | memset(&spinlock_stats, 0, sizeof(spinlock_stats)); | |
994025ca JF |
50 | } |
51 | } | |
52 | ||
80bd58fe JF |
53 | static inline void add_stats(enum xen_contention_stat var, u32 val) |
54 | { | |
55 | check_zero(); | |
56 | spinlock_stats.contention_stats[var] += val; | |
57 | } | |
994025ca JF |
58 | |
59 | static inline u64 spin_time_start(void) | |
60 | { | |
61 | return xen_clocksource_read(); | |
62 | } | |
63 | ||
64 | static void __spin_time_accum(u64 delta, u32 *array) | |
65 | { | |
66 | unsigned index = ilog2(delta); | |
67 | ||
68 | check_zero(); | |
69 | ||
70 | if (index < HISTO_BUCKETS) | |
71 | array[index]++; | |
72 | else | |
73 | array[HISTO_BUCKETS]++; | |
74 | } | |
75 | ||
f8eca41f | 76 | static inline void spin_time_accum_blocked(u64 start) |
994025ca JF |
77 | { |
78 | u32 delta = xen_clocksource_read() - start; | |
79 | ||
f8eca41f JF |
80 | __spin_time_accum(delta, spinlock_stats.histo_spin_blocked); |
81 | spinlock_stats.time_blocked += delta; | |
994025ca JF |
82 | } |
83 | #else /* !CONFIG_XEN_DEBUG_FS */ | |
84 | #define TIMEOUT (1 << 10) | |
80bd58fe JF |
85 | static inline void add_stats(enum xen_contention_stat var, u32 val) |
86 | { | |
87 | } | |
994025ca JF |
88 | |
89 | static inline u64 spin_time_start(void) | |
90 | { | |
91 | return 0; | |
92 | } | |
93 | ||
f8eca41f | 94 | static inline void spin_time_accum_blocked(u64 start) |
994025ca JF |
95 | { |
96 | } | |
97 | #endif /* CONFIG_XEN_DEBUG_FS */ | |
d5de8841 | 98 | |
7a7546b3 DV |
99 | /* |
100 | * Size struct xen_spinlock so it's the same as arch_spinlock_t. | |
101 | */ | |
102 | #if NR_CPUS < 256 | |
103 | typedef u8 xen_spinners_t; | |
104 | # define inc_spinners(xl) \ | |
105 | asm(LOCK_PREFIX " incb %0" : "+m" ((xl)->spinners) : : "memory"); | |
106 | # define dec_spinners(xl) \ | |
107 | asm(LOCK_PREFIX " decb %0" : "+m" ((xl)->spinners) : : "memory"); | |
108 | #else | |
109 | typedef u16 xen_spinners_t; | |
110 | # define inc_spinners(xl) \ | |
111 | asm(LOCK_PREFIX " incw %0" : "+m" ((xl)->spinners) : : "memory"); | |
112 | # define dec_spinners(xl) \ | |
113 | asm(LOCK_PREFIX " decw %0" : "+m" ((xl)->spinners) : : "memory"); | |
114 | #endif | |
115 | ||
80bd58fe JF |
116 | struct xen_lock_waiting { |
117 | struct arch_spinlock *lock; | |
118 | __ticket_t want; | |
d5de8841 JF |
119 | }; |
120 | ||
545ac138 | 121 | static DEFINE_PER_CPU(int, lock_kicker_irq) = -1; |
354e7b76 | 122 | static DEFINE_PER_CPU(char *, irq_name); |
80bd58fe JF |
123 | static DEFINE_PER_CPU(struct xen_lock_waiting, lock_waiting); |
124 | static cpumask_t waiting_cpus; | |
d5de8841 | 125 | |
80bd58fe | 126 | static void xen_lock_spinning(struct arch_spinlock *lock, __ticket_t want) |
d5de8841 | 127 | { |
780f36d8 | 128 | int irq = __this_cpu_read(lock_kicker_irq); |
80bd58fe JF |
129 | struct xen_lock_waiting *w = &__get_cpu_var(lock_waiting); |
130 | int cpu = smp_processor_id(); | |
f8eca41f | 131 | u64 start; |
80bd58fe | 132 | unsigned long flags; |
d5de8841 JF |
133 | |
134 | /* If kicker interrupts not initialized yet, just spin */ | |
135 | if (irq == -1) | |
80bd58fe | 136 | return; |
d5de8841 | 137 | |
f8eca41f JF |
138 | start = spin_time_start(); |
139 | ||
80bd58fe JF |
140 | /* |
141 | * Make sure an interrupt handler can't upset things in a | |
142 | * partially setup state. | |
143 | */ | |
144 | local_irq_save(flags); | |
d5de8841 | 145 | |
80bd58fe JF |
146 | w->want = want; |
147 | smp_wmb(); | |
148 | w->lock = lock; | |
4d576b57 | 149 | |
80bd58fe JF |
150 | /* This uses set_bit, which atomic and therefore a barrier */ |
151 | cpumask_set_cpu(cpu, &waiting_cpus); | |
152 | add_stats(TAKEN_SLOW, 1); | |
4d576b57 | 153 | |
80bd58fe JF |
154 | /* clear pending */ |
155 | xen_clear_irq_pending(irq); | |
4d576b57 | 156 | |
80bd58fe JF |
157 | /* Only check lock once pending cleared */ |
158 | barrier(); | |
d5de8841 | 159 | |
80bd58fe JF |
160 | /* check again make sure it didn't become free while |
161 | we weren't looking */ | |
162 | if (ACCESS_ONCE(lock->tickets.head) == want) { | |
163 | add_stats(TAKEN_SLOW_PICKUP, 1); | |
164 | goto out; | |
165 | } | |
166 | /* Block until irq becomes pending (or perhaps a spurious wakeup) */ | |
167 | xen_poll_irq(irq); | |
168 | add_stats(TAKEN_SLOW_SPURIOUS, !xen_test_irq_pending(irq)); | |
d6c88a50 | 169 | kstat_incr_irqs_this_cpu(irq, irq_to_desc(irq)); |
d5de8841 | 170 | out: |
80bd58fe JF |
171 | cpumask_clear_cpu(cpu, &waiting_cpus); |
172 | w->lock = NULL; | |
173 | local_irq_restore(flags); | |
f8eca41f | 174 | spin_time_accum_blocked(start); |
d5de8841 | 175 | } |
354714dd | 176 | PV_CALLEE_SAVE_REGS_THUNK(xen_lock_spinning); |
d5de8841 | 177 | |
80bd58fe | 178 | static void xen_unlock_kick(struct arch_spinlock *lock, __ticket_t next) |
d5de8841 JF |
179 | { |
180 | int cpu; | |
181 | ||
80bd58fe JF |
182 | add_stats(RELEASED_SLOW, 1); |
183 | ||
184 | for_each_cpu(cpu, &waiting_cpus) { | |
185 | const struct xen_lock_waiting *w = &per_cpu(lock_waiting, cpu); | |
994025ca | 186 | |
80bd58fe JF |
187 | if (w->lock == lock && w->want == next) { |
188 | add_stats(RELEASED_SLOW_KICKED, 1); | |
d5de8841 | 189 | xen_send_IPI_one(cpu, XEN_SPIN_UNLOCK_VECTOR); |
80bd58fe | 190 | break; |
d5de8841 JF |
191 | } |
192 | } | |
193 | } | |
194 | ||
d5de8841 JF |
195 | static irqreturn_t dummy_handler(int irq, void *dev_id) |
196 | { | |
197 | BUG(); | |
198 | return IRQ_HANDLED; | |
199 | } | |
200 | ||
148f9bb8 | 201 | void xen_init_lock_cpu(int cpu) |
d5de8841 JF |
202 | { |
203 | int irq; | |
354e7b76 | 204 | char *name; |
d5de8841 | 205 | |
cb91f8f4 | 206 | WARN(per_cpu(lock_kicker_irq, cpu) >= 0, "spinlock on CPU%d exists on IRQ%d!\n", |
cb9c6f15 KRW |
207 | cpu, per_cpu(lock_kicker_irq, cpu)); |
208 | ||
70dd4998 KRW |
209 | /* |
210 | * See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23 | |
211 | * (xen: disable PV spinlocks on HVM) | |
212 | */ | |
213 | if (xen_hvm_domain()) | |
214 | return; | |
215 | ||
d5de8841 JF |
216 | name = kasprintf(GFP_KERNEL, "spinlock%d", cpu); |
217 | irq = bind_ipi_to_irqhandler(XEN_SPIN_UNLOCK_VECTOR, | |
218 | cpu, | |
219 | dummy_handler, | |
220 | IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING, | |
221 | name, | |
222 | NULL); | |
223 | ||
224 | if (irq >= 0) { | |
225 | disable_irq(irq); /* make sure it's never delivered */ | |
226 | per_cpu(lock_kicker_irq, cpu) = irq; | |
354e7b76 | 227 | per_cpu(irq_name, cpu) = name; |
d5de8841 JF |
228 | } |
229 | ||
230 | printk("cpu %d spinlock event irq %d\n", cpu, irq); | |
231 | } | |
232 | ||
d68d82af AN |
233 | void xen_uninit_lock_cpu(int cpu) |
234 | { | |
70dd4998 KRW |
235 | /* |
236 | * See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23 | |
237 | * (xen: disable PV spinlocks on HVM) | |
238 | */ | |
239 | if (xen_hvm_domain()) | |
240 | return; | |
241 | ||
d68d82af | 242 | unbind_from_irqhandler(per_cpu(lock_kicker_irq, cpu), NULL); |
cb9c6f15 | 243 | per_cpu(lock_kicker_irq, cpu) = -1; |
354e7b76 KRW |
244 | kfree(per_cpu(irq_name, cpu)); |
245 | per_cpu(irq_name, cpu) = NULL; | |
d68d82af AN |
246 | } |
247 | ||
b8fa70b5 JF |
248 | static bool xen_pvspin __initdata = true; |
249 | ||
d5de8841 JF |
250 | void __init xen_init_spinlocks(void) |
251 | { | |
70dd4998 KRW |
252 | /* |
253 | * See git commit f10cd522c5fbfec9ae3cc01967868c9c2401ed23 | |
254 | * (xen: disable PV spinlocks on HVM) | |
255 | */ | |
256 | if (xen_hvm_domain()) | |
257 | return; | |
258 | ||
b8fa70b5 JF |
259 | if (!xen_pvspin) { |
260 | printk(KERN_DEBUG "xen: PV spinlocks disabled\n"); | |
261 | return; | |
262 | } | |
263 | ||
354714dd | 264 | pv_lock_ops.lock_spinning = PV_CALLEE_SAVE(xen_lock_spinning); |
80bd58fe | 265 | pv_lock_ops.unlock_kick = xen_unlock_kick; |
d5de8841 | 266 | } |
994025ca | 267 | |
b8fa70b5 JF |
268 | static __init int xen_parse_nopvspin(char *arg) |
269 | { | |
270 | xen_pvspin = false; | |
271 | return 0; | |
272 | } | |
273 | early_param("xen_nopvspin", xen_parse_nopvspin); | |
274 | ||
994025ca JF |
275 | #ifdef CONFIG_XEN_DEBUG_FS |
276 | ||
277 | static struct dentry *d_spin_debug; | |
278 | ||
279 | static int __init xen_spinlock_debugfs(void) | |
280 | { | |
281 | struct dentry *d_xen = xen_init_debugfs(); | |
282 | ||
283 | if (d_xen == NULL) | |
284 | return -ENOMEM; | |
285 | ||
286 | d_spin_debug = debugfs_create_dir("spinlocks", d_xen); | |
287 | ||
288 | debugfs_create_u8("zero_stats", 0644, d_spin_debug, &zero_stats); | |
289 | ||
994025ca | 290 | debugfs_create_u32("taken_slow", 0444, d_spin_debug, |
80bd58fe | 291 | &spinlock_stats.contention_stats[TAKEN_SLOW]); |
994025ca | 292 | debugfs_create_u32("taken_slow_pickup", 0444, d_spin_debug, |
80bd58fe | 293 | &spinlock_stats.contention_stats[TAKEN_SLOW_PICKUP]); |
994025ca | 294 | debugfs_create_u32("taken_slow_spurious", 0444, d_spin_debug, |
80bd58fe | 295 | &spinlock_stats.contention_stats[TAKEN_SLOW_SPURIOUS]); |
994025ca | 296 | |
994025ca | 297 | debugfs_create_u32("released_slow", 0444, d_spin_debug, |
80bd58fe | 298 | &spinlock_stats.contention_stats[RELEASED_SLOW]); |
994025ca | 299 | debugfs_create_u32("released_slow_kicked", 0444, d_spin_debug, |
80bd58fe | 300 | &spinlock_stats.contention_stats[RELEASED_SLOW_KICKED]); |
994025ca | 301 | |
f8eca41f JF |
302 | debugfs_create_u64("time_blocked", 0444, d_spin_debug, |
303 | &spinlock_stats.time_blocked); | |
994025ca | 304 | |
9fe2a701 SV |
305 | debugfs_create_u32_array("histo_blocked", 0444, d_spin_debug, |
306 | spinlock_stats.histo_spin_blocked, HISTO_BUCKETS + 1); | |
994025ca JF |
307 | |
308 | return 0; | |
309 | } | |
310 | fs_initcall(xen_spinlock_debugfs); | |
311 | ||
312 | #endif /* CONFIG_XEN_DEBUG_FS */ |