# HG changeset patch
# User Keir Fraser <keir@xxxxxxx>
# Date 1290766077 0
# Node ID aee9a8f63aaefb1a3801eea2f7d9cddfeb5486df
# Parent 79b71c77907b80772ee8cba0c5bbf8e444e61226
cpupool: Simplify locking, use refcounts for cpupool liveness.
Signed-off-by: Keir Fraser <keir@xxxxxxx>
---
xen/common/cpupool.c | 82 +++++++++++++++++++++++++--------------------
xen/common/schedule.c | 9 +---
xen/include/xen/sched-if.h | 1
3 files changed, 49 insertions(+), 43 deletions(-)
diff -r 79b71c77907b -r aee9a8f63aae xen/common/cpupool.c
--- a/xen/common/cpupool.c Wed Nov 24 10:20:03 2010 +0000
+++ b/xen/common/cpupool.c Fri Nov 26 10:07:57 2010 +0000
@@ -31,11 +31,7 @@ static struct cpupool *cpupool_cpu_movin
static struct cpupool *cpupool_cpu_moving = NULL;
static cpumask_t cpupool_locked_cpus = CPU_MASK_NONE;
-/* cpupool lock: be carefull, this lock is sometimes released on another cpu
- * as it was obtained!
- */
static DEFINE_SPINLOCK(cpupool_lock);
-static DEFINE_SPINLOCK(cpupool_ctl_lock);
DEFINE_PER_CPU(struct cpupool *, cpupool);
@@ -61,30 +57,37 @@ static struct cpupool *cpupool_find_by_i
{
struct cpupool **q;
+ ASSERT(spin_is_locked(&cpupool_lock));
+
for_each_cpupool(q)
- {
- if ( (*q)->cpupool_id == id )
- return *q;
- if ( (*q)->cpupool_id > id )
- break;
- }
- return exact ? NULL : *q;
+ if ( (*q)->cpupool_id >= id )
+ break;
+
+ return (!exact || ((*q)->cpupool_id == id)) ? *q : NULL;
+}
+
+static struct cpupool *__cpupool_get_by_id(int poolid, int exact)
+{
+ struct cpupool *c;
+ spin_lock(&cpupool_lock);
+ c = cpupool_find_by_id(poolid, exact);
+ if ( c != NULL )
+ atomic_inc(&c->refcnt);
+ spin_unlock(&cpupool_lock);
+ return c;
}
struct cpupool *cpupool_get_by_id(int poolid)
{
- struct cpupool *c;
- /* cpupool_ctl_lock protects against concurrent pool destruction */
- spin_lock(&cpupool_ctl_lock);
- c = cpupool_find_by_id(poolid, 1);
- if ( c == NULL )
- spin_unlock(&cpupool_ctl_lock);
- return c;
+ return __cpupool_get_by_id(poolid, 1);
}
void cpupool_put(struct cpupool *pool)
{
- spin_unlock(&cpupool_ctl_lock);
+ if ( !atomic_dec_and_test(&pool->refcnt) )
+ return;
+ scheduler_free(pool->sched);
+ free_cpupool_struct(pool);
}
/*
@@ -107,6 +110,9 @@ static struct cpupool *cpupool_create(
return NULL;
memset(c, 0, sizeof(*c));
+ /* One reference for caller, one reference for cpupool_destroy(). */
+ atomic_set(&c->refcnt, 2);
+
cpupool_dprintk("cpupool_create(pool=%d,sched=%u)\n", poolid, sched_id);
spin_lock(&cpupool_lock);
@@ -183,9 +189,10 @@ static int cpupool_destroy(struct cpupoo
}
*q = c->next;
spin_unlock(&cpupool_lock);
+
+ cpupool_put(c);
+
cpupool_dprintk("cpupool_destroy(pool=%d)\n", c->cpupool_id);
- scheduler_free(c->sched);
- free_cpupool_struct(c);
return 0;
}
@@ -203,6 +210,7 @@ static int cpupool_assign_cpu_locked(str
if (cpupool_moving_cpu == cpu)
{
cpupool_moving_cpu = -1;
+ cpupool_put(cpupool_cpu_moving);
cpupool_cpu_moving = NULL;
}
cpu_set(cpu, c->cpu_valid);
@@ -217,6 +225,7 @@ static long cpupool_unassign_cpu_helper(
cpupool_dprintk("cpupool_unassign_cpu(pool=%d,cpu=%d) ret %ld\n",
cpupool_id, cpu, ret);
+ spin_lock(&cpupool_lock);
ret = cpu_disable_scheduler(cpu);
cpu_set(cpu, cpupool_free_cpus);
if ( !ret )
@@ -224,6 +233,7 @@ static long cpupool_unassign_cpu_helper(
schedule_cpu_switch(cpu, NULL);
per_cpu(cpupool, cpu) = NULL;
cpupool_moving_cpu = -1;
+ cpupool_put(cpupool_cpu_moving);
cpupool_cpu_moving = NULL;
}
spin_unlock(&cpupool_lock);
@@ -287,8 +297,11 @@ int cpupool_unassign_cpu(struct cpupool
goto out;
}
cpupool_moving_cpu = cpu;
+ atomic_inc(&c->refcnt);
cpupool_cpu_moving = c;
cpu_clear(cpu, c->cpu_valid);
+ spin_unlock(&cpupool_lock);
+
work_cpu = smp_processor_id();
if ( work_cpu == cpu )
{
@@ -395,8 +408,6 @@ int cpupool_do_sysctl(struct xen_sysctl_
int ret;
struct cpupool *c;
- spin_lock(&cpupool_ctl_lock);
-
switch ( op->op )
{
@@ -408,30 +419,35 @@ int cpupool_do_sysctl(struct xen_sysctl_
CPUPOOLID_NONE: op->cpupool_id;
c = cpupool_create(poolid, op->sched_id, &ret);
if ( c != NULL )
+ {
op->cpupool_id = c->cpupool_id;
+ cpupool_put(c);
+ }
}
break;
case XEN_SYSCTL_CPUPOOL_OP_DESTROY:
{
- c = cpupool_find_by_id(op->cpupool_id, 1);
+ c = cpupool_get_by_id(op->cpupool_id);
ret = -ENOENT;
if ( c == NULL )
break;
ret = cpupool_destroy(c);
+ cpupool_put(c);
}
break;
case XEN_SYSCTL_CPUPOOL_OP_INFO:
{
- c = cpupool_find_by_id(op->cpupool_id, 0);
+ c = __cpupool_get_by_id(op->cpupool_id, 0);
ret = -ENOENT;
if ( c == NULL )
break;
op->cpupool_id = c->cpupool_id;
op->sched_id = c->sched->sched_id;
op->n_dom = c->n_dom;
- ret = cpumask_to_xenctl_cpumap(&(op->cpumap), &(c->cpu_valid));
+ ret = cpumask_to_xenctl_cpumap(&op->cpumap, &c->cpu_valid);
+ cpupool_put(c);
}
break;
@@ -467,20 +483,15 @@ int cpupool_do_sysctl(struct xen_sysctl_
{
unsigned cpu;
- c = cpupool_find_by_id(op->cpupool_id, 0);
+ c = __cpupool_get_by_id(op->cpupool_id, 0);
ret = -ENOENT;
if ( c == NULL )
break;
cpu = op->cpu;
if ( cpu == XEN_SYSCTL_CPUPOOL_PAR_ANY )
cpu = last_cpu(c->cpu_valid);
- ret = -EINVAL;
- if ( cpu >= NR_CPUS )
- break;
- /* caution: cpupool_unassign_cpu uses continue_hypercall_on_cpu and
- * will continue after the local return
- */
- ret = cpupool_unassign_cpu(c, cpu);
+ ret = (cpu < NR_CPUS) ? cpupool_unassign_cpu(c, cpu) : -EINVAL;
+ cpupool_put(c);
}
break;
@@ -539,8 +550,6 @@ int cpupool_do_sysctl(struct xen_sysctl_
ret = -ENOSYS;
break;
}
-
- spin_unlock(&cpupool_ctl_lock);
return ret;
}
@@ -605,6 +614,7 @@ static int __init cpupool_presmp_init(vo
void *cpu = (void *)(long)smp_processor_id();
cpupool0 = cpupool_create(0, 0, &err);
BUG_ON(cpupool0 == NULL);
+ cpupool_put(cpupool0);
cpu_callback(&cpu_nfb, CPU_ONLINE, cpu);
register_cpu_notifier(&cpu_nfb);
return 0;
diff -r 79b71c77907b -r aee9a8f63aae xen/common/schedule.c
--- a/xen/common/schedule.c Wed Nov 24 10:20:03 2010 +0000
+++ b/xen/common/schedule.c Fri Nov 26 10:07:57 2010 +0000
@@ -999,13 +999,8 @@ long sched_adjust_global(struct xen_sysc
if ( pool == NULL )
return -ESRCH;
- if ( op->sched_id != pool->sched->sched_id )
- {
- cpupool_put(pool);
- return -EINVAL;
- }
-
- rc = SCHED_OP(pool->sched, adjust_global, op);
+ rc = ((op->sched_id == pool->sched->sched_id)
+ ? SCHED_OP(pool->sched, adjust_global, op) : -EINVAL);
cpupool_put(pool);
diff -r 79b71c77907b -r aee9a8f63aae xen/include/xen/sched-if.h
--- a/xen/include/xen/sched-if.h Wed Nov 24 10:20:03 2010 +0000
+++ b/xen/include/xen/sched-if.h Fri Nov 26 10:07:57 2010 +0000
@@ -133,6 +133,7 @@ struct cpupool
struct cpupool *next;
unsigned int n_dom;
struct scheduler *sched;
+ atomic_t refcnt;
};
#endif /* __XEN_SCHED_IF_H__ */
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