diff options
author | Nathan Lynch <ntl@pobox.com> | 2007-05-22 20:51:25 -0400 |
---|---|---|
committer | Paul Mackerras <paulus@samba.org> | 2007-06-25 02:58:11 -0400 |
commit | df211c8a478e16232ebbc16e650b19163183fcb6 (patch) | |
tree | 90972e63f445e0edad7a195a025ad3fffa9283f3 /arch/powerpc/kernel | |
parent | 1a06e0fe96526e43bab90fbab2263b55fb3d45d1 (diff) |
[POWERPC] Remove spinlock from struct cpu_purr_data
cpu_purr_data is a per-cpu array used to account for stolen time on
partitioned systems. It used to be the case that cpus accessed each
others' cpu_purr_data, so each entry was protected by a spinlock.
However, the code was reworked ("Simplify stolen time calculation")
with the result that each cpu accesses its own cpu_purr_data and not
those of other cpus. This means we can get rid of the spinlock as
long as we're careful to disable interrupts when accessing
cpu_purr_data in process context.
Signed-off-by: Nathan Lynch <ntl@pobox.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
Diffstat (limited to 'arch/powerpc/kernel')
-rw-r--r-- | arch/powerpc/kernel/time.c | 24 |
1 files changed, 15 insertions, 9 deletions
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 2c8564d54e4d..0a8a820672f4 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c | |||
@@ -222,19 +222,28 @@ struct cpu_purr_data { | |||
222 | int initialized; /* thread is running */ | 222 | int initialized; /* thread is running */ |
223 | u64 tb; /* last TB value read */ | 223 | u64 tb; /* last TB value read */ |
224 | u64 purr; /* last PURR value read */ | 224 | u64 purr; /* last PURR value read */ |
225 | spinlock_t lock; | ||
226 | }; | 225 | }; |
227 | 226 | ||
227 | /* | ||
228 | * Each entry in the cpu_purr_data array is manipulated only by its | ||
229 | * "owner" cpu -- usually in the timer interrupt but also occasionally | ||
230 | * in process context for cpu online. As long as cpus do not touch | ||
231 | * each others' cpu_purr_data, disabling local interrupts is | ||
232 | * sufficient to serialize accesses. | ||
233 | */ | ||
228 | static DEFINE_PER_CPU(struct cpu_purr_data, cpu_purr_data); | 234 | static DEFINE_PER_CPU(struct cpu_purr_data, cpu_purr_data); |
229 | 235 | ||
230 | static void snapshot_tb_and_purr(void *data) | 236 | static void snapshot_tb_and_purr(void *data) |
231 | { | 237 | { |
238 | unsigned long flags; | ||
232 | struct cpu_purr_data *p = &__get_cpu_var(cpu_purr_data); | 239 | struct cpu_purr_data *p = &__get_cpu_var(cpu_purr_data); |
233 | 240 | ||
241 | local_irq_save(flags); | ||
234 | p->tb = mftb(); | 242 | p->tb = mftb(); |
235 | p->purr = mfspr(SPRN_PURR); | 243 | p->purr = mfspr(SPRN_PURR); |
236 | wmb(); | 244 | wmb(); |
237 | p->initialized = 1; | 245 | p->initialized = 1; |
246 | local_irq_restore(flags); | ||
238 | } | 247 | } |
239 | 248 | ||
240 | /* | 249 | /* |
@@ -242,15 +251,14 @@ static void snapshot_tb_and_purr(void *data) | |||
242 | */ | 251 | */ |
243 | void snapshot_timebases(void) | 252 | void snapshot_timebases(void) |
244 | { | 253 | { |
245 | int cpu; | ||
246 | |||
247 | if (!cpu_has_feature(CPU_FTR_PURR)) | 254 | if (!cpu_has_feature(CPU_FTR_PURR)) |
248 | return; | 255 | return; |
249 | for_each_possible_cpu(cpu) | ||
250 | spin_lock_init(&per_cpu(cpu_purr_data, cpu).lock); | ||
251 | on_each_cpu(snapshot_tb_and_purr, NULL, 0, 1); | 256 | on_each_cpu(snapshot_tb_and_purr, NULL, 0, 1); |
252 | } | 257 | } |
253 | 258 | ||
259 | /* | ||
260 | * Must be called with interrupts disabled. | ||
261 | */ | ||
254 | void calculate_steal_time(void) | 262 | void calculate_steal_time(void) |
255 | { | 263 | { |
256 | u64 tb, purr; | 264 | u64 tb, purr; |
@@ -262,7 +270,6 @@ void calculate_steal_time(void) | |||
262 | pme = &per_cpu(cpu_purr_data, smp_processor_id()); | 270 | pme = &per_cpu(cpu_purr_data, smp_processor_id()); |
263 | if (!pme->initialized) | 271 | if (!pme->initialized) |
264 | return; /* this can happen in early boot */ | 272 | return; /* this can happen in early boot */ |
265 | spin_lock(&pme->lock); | ||
266 | tb = mftb(); | 273 | tb = mftb(); |
267 | purr = mfspr(SPRN_PURR); | 274 | purr = mfspr(SPRN_PURR); |
268 | stolen = (tb - pme->tb) - (purr - pme->purr); | 275 | stolen = (tb - pme->tb) - (purr - pme->purr); |
@@ -270,7 +277,6 @@ void calculate_steal_time(void) | |||
270 | account_steal_time(current, stolen); | 277 | account_steal_time(current, stolen); |
271 | pme->tb = tb; | 278 | pme->tb = tb; |
272 | pme->purr = purr; | 279 | pme->purr = purr; |
273 | spin_unlock(&pme->lock); | ||
274 | } | 280 | } |
275 | 281 | ||
276 | /* | 282 | /* |
@@ -284,12 +290,12 @@ static void snapshot_purr(void) | |||
284 | 290 | ||
285 | if (!cpu_has_feature(CPU_FTR_PURR)) | 291 | if (!cpu_has_feature(CPU_FTR_PURR)) |
286 | return; | 292 | return; |
293 | local_irq_save(flags); | ||
287 | pme = &per_cpu(cpu_purr_data, smp_processor_id()); | 294 | pme = &per_cpu(cpu_purr_data, smp_processor_id()); |
288 | spin_lock_irqsave(&pme->lock, flags); | ||
289 | pme->tb = mftb(); | 295 | pme->tb = mftb(); |
290 | pme->purr = mfspr(SPRN_PURR); | 296 | pme->purr = mfspr(SPRN_PURR); |
291 | pme->initialized = 1; | 297 | pme->initialized = 1; |
292 | spin_unlock_irqrestore(&pme->lock, flags); | 298 | local_irq_restore(flags); |
293 | } | 299 | } |
294 | 300 | ||
295 | #endif /* CONFIG_PPC_SPLPAR */ | 301 | #endif /* CONFIG_PPC_SPLPAR */ |