Mailing List Archive

In order to prepare not allocating or freeing memory from
schedule_cpu_rm(), move this functionality to dedicated functions.

For now call those functions from schedule_cpu_rm().

No change of behavior expected.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2:
- add const (Jan Beulich)
- use "unsigned int" for loop index (Jan Beulich)
- use xmalloc_flex_struct() (Jan Beulich)
- use XFREE() (Jan Beulich)
- hold rcu lock longer (Jan Beulich)
- add ASSERT() (Jan Beulich)
V3:
- added comment for schedule_cpu_rm_alloc() (Jan Beulich)
---
xen/common/sched/core.c | 143 ++++++++++++++++++++++---------------
xen/common/sched/private.h | 9 +++
2 files changed, 96 insertions(+), 56 deletions(-)

diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
index f6eed88930..228470ac41 100644
--- a/xen/common/sched/core.c
+++ b/xen/common/sched/core.c
@@ -3237,6 +3237,75 @@ out:
return ret;
}

+/*
+ * Allocate all memory needed for schedule_cpu_rm_free(), which can't do that
+ * due to be called in stop_machine() context with interrupts disabled.
+ *
+ * Between schedule_cpu_rm_alloc() and the real cpu removal action the relevant
+ * contents of struct sched_resource can't change, as the cpu in question is
+ * locked against any other movement to or from cpupools, and the data copied
+ * by schedule_cpu_rm_alloc() is modified only in case the cpu in question is
+ * being moved from or to a cpupool.
+ */
+static struct cpu_rm_data *schedule_cpu_rm_alloc(unsigned int cpu)
+{
+ struct cpu_rm_data *data;
+ const struct sched_resource *sr;
+ unsigned int idx;
+
+ rcu_read_lock(&sched_res_rculock);
+
+ sr = get_sched_res(cpu);
+ data = xmalloc_flex_struct(struct cpu_rm_data, sr, sr->granularity - 1);
+ if ( !data )
+ goto out;
+
+ data->old_ops = sr->scheduler;
+ data->vpriv_old = idle_vcpu[cpu]->sched_unit->priv;
+ data->ppriv_old = sr->sched_priv;
+
+ for ( idx = 0; idx < sr->granularity - 1; idx++ )
+ {
+ data->sr[idx] = sched_alloc_res();
+ if ( data->sr[idx] )
+ {
+ data->sr[idx]->sched_unit_idle = sched_alloc_unit_mem();
+ if ( !data->sr[idx]->sched_unit_idle )
+ {
+ sched_res_free(&data->sr[idx]->rcu);
+ data->sr[idx] = NULL;
+ }
+ }
+ if ( !data->sr[idx] )
+ {
+ while ( idx > 0 )
+ sched_res_free(&data->sr[--idx]->rcu);
+ XFREE(data);
+ goto out;
+ }
+
+ data->sr[idx]->curr = data->sr[idx]->sched_unit_idle;
+ data->sr[idx]->scheduler = &sched_idle_ops;
+ data->sr[idx]->granularity = 1;
+
+ /* We want the lock not to change when replacing the resource. */
+ data->sr[idx]->schedule_lock = sr->schedule_lock;
+ }
+
+ out:
+ rcu_read_unlock(&sched_res_rculock);
+
+ return data;
+}
+
+static void schedule_cpu_rm_free(struct cpu_rm_data *mem, unsigned int cpu)
+{
+ sched_free_udata(mem->old_ops, mem->vpriv_old);
+ sched_free_pdata(mem->old_ops, mem->ppriv_old, cpu);
+
+ xfree(mem);
+}
+
/*
* Remove a pCPU from its cpupool. Its scheduler becomes &sched_idle_ops
* (the idle scheduler).
@@ -3245,53 +3314,23 @@ out:
*/
int schedule_cpu_rm(unsigned int cpu)
{
- void *ppriv_old, *vpriv_old;
- struct sched_resource *sr, **sr_new = NULL;
+ struct sched_resource *sr;
+ struct cpu_rm_data *data;
struct sched_unit *unit;
- struct scheduler *old_ops;
spinlock_t *old_lock;
unsigned long flags;
- int idx, ret = -ENOMEM;
+ int idx = 0;
unsigned int cpu_iter;

+ data = schedule_cpu_rm_alloc(cpu);
+ if ( !data )
+ return -ENOMEM;
+
rcu_read_lock(&sched_res_rculock);

sr = get_sched_res(cpu);
- old_ops = sr->scheduler;
-
- if ( sr->granularity > 1 )
- {
- sr_new = xmalloc_array(struct sched_resource *, sr->granularity - 1);
- if ( !sr_new )
- goto out;
- for ( idx = 0; idx < sr->granularity - 1; idx++ )
- {
- sr_new[idx] = sched_alloc_res();
- if ( sr_new[idx] )
- {
- sr_new[idx]->sched_unit_idle = sched_alloc_unit_mem();
- if ( !sr_new[idx]->sched_unit_idle )
- {
- sched_res_free(&sr_new[idx]->rcu);
- sr_new[idx] = NULL;
- }
- }
- if ( !sr_new[idx] )
- {
- for ( idx--; idx >= 0; idx-- )
- sched_res_free(&sr_new[idx]->rcu);
- goto out;
- }
- sr_new[idx]->curr = sr_new[idx]->sched_unit_idle;
- sr_new[idx]->scheduler = &sched_idle_ops;
- sr_new[idx]->granularity = 1;

- /* We want the lock not to change when replacing the resource. */
- sr_new[idx]->schedule_lock = sr->schedule_lock;
- }
- }
-
- ret = 0;
+ ASSERT(sr->granularity);
ASSERT(sr->cpupool != NULL);
ASSERT(cpumask_test_cpu(cpu, &cpupool_free_cpus));
ASSERT(!cpumask_test_cpu(cpu, sr->cpupool->cpu_valid));
@@ -3299,10 +3338,6 @@ int schedule_cpu_rm(unsigned int cpu)
/* See comment in schedule_cpu_add() regarding lock switching. */
old_lock = pcpu_schedule_lock_irqsave(cpu, &flags);

- vpriv_old = idle_vcpu[cpu]->sched_unit->priv;
- ppriv_old = sr->sched_priv;
-
- idx = 0;
for_each_cpu ( cpu_iter, sr->cpus )
{
per_cpu(sched_res_idx, cpu_iter) = 0;
@@ -3316,27 +3351,27 @@ int schedule_cpu_rm(unsigned int cpu)
else
{
/* Initialize unit. */
- unit = sr_new[idx]->sched_unit_idle;
- unit->res = sr_new[idx];
+ unit = data->sr[idx]->sched_unit_idle;
+ unit->res = data->sr[idx];
unit->is_running = true;
sched_unit_add_vcpu(unit, idle_vcpu[cpu_iter]);
sched_domain_insert_unit(unit, idle_vcpu[cpu_iter]->domain);

/* Adjust cpu masks of resources (old and new). */
cpumask_clear_cpu(cpu_iter, sr->cpus);
- cpumask_set_cpu(cpu_iter, sr_new[idx]->cpus);
+ cpumask_set_cpu(cpu_iter, data->sr[idx]->cpus);
cpumask_set_cpu(cpu_iter, &sched_res_mask);

/* Init timer. */
- init_timer(&sr_new[idx]->s_timer, s_timer_fn, NULL, cpu_iter);
+ init_timer(&data->sr[idx]->s_timer, s_timer_fn, NULL, cpu_iter);

/* Last resource initializations and insert resource pointer. */
- sr_new[idx]->master_cpu = cpu_iter;
- set_sched_res(cpu_iter, sr_new[idx]);
+ data->sr[idx]->master_cpu = cpu_iter;
+ set_sched_res(cpu_iter, data->sr[idx]);

/* Last action: set the new lock pointer. */
smp_mb();
- sr_new[idx]->schedule_lock = &sched_free_cpu_lock;
+ data->sr[idx]->schedule_lock = &sched_free_cpu_lock;

idx++;
}
@@ -3352,16 +3387,12 @@ int schedule_cpu_rm(unsigned int cpu)
/* _Not_ pcpu_schedule_unlock(): schedule_lock may have changed! */
spin_unlock_irqrestore(old_lock, flags);

- sched_deinit_pdata(old_ops, ppriv_old, cpu);
-
- sched_free_udata(old_ops, vpriv_old);
- sched_free_pdata(old_ops, ppriv_old, cpu);
+ sched_deinit_pdata(data->old_ops, data->ppriv_old, cpu);

-out:
rcu_read_unlock(&sched_res_rculock);
- xfree(sr_new);
+ schedule_cpu_rm_free(data, cpu);

- return ret;
+ return 0;
}

struct scheduler *scheduler_get_default(void)
diff --git a/xen/common/sched/private.h b/xen/common/sched/private.h
index 38251b1f7b..601d639699 100644
--- a/xen/common/sched/private.h
+++ b/xen/common/sched/private.h
@@ -600,6 +600,15 @@ struct affinity_masks {

bool update_node_aff_alloc(struct affinity_masks *affinity);
void update_node_aff_free(struct affinity_masks *affinity);
+
+/* Memory allocation related data for schedule_cpu_rm(). */
+struct cpu_rm_data {
+ const struct scheduler *old_ops;
+ void *ppriv_old;
+ void *vpriv_old;
+ struct sched_resource *sr[];
+};
+
void sched_rm_cpu(unsigned int cpu);
const cpumask_t *sched_get_opt_cpumask(enum sched_gran opt, unsigned int cpu);
void schedule_dump(struct cpupool *c);
--
2.35.3