On Thursday 29 June 2017 01:11 AM, Thomas Gleixner wrote:
On Thu, 29 Jun 2017, Anju T Sudhakar wrote:
+static void cleanup_all_core_imc_memory(struct imc_pmu *pmu_ptr)
+{
+ struct imc_mem_info *ptr;
+
+ for (ptr = pmu_ptr->mem_info; ptr; ptr++) {
+ if (ptr->vbase[0])
+ free_pages((u64)ptr->vbase[0], 0);
+ }
This loop is broken beyond repair. If pmu_ptr->mem_info is not NULL, then
ptr will happily increment to the point where it wraps around to
NULL. Oh well.
+ kfree(pmu_ptr->mem_info);
+bool is_core_imc_mem_inited(int cpu)
This function is global because?
+{
+ struct imc_mem_info *mem_info;
+ int core_id = (cpu / threads_per_core);
+
+ mem_info = &core_imc_pmu->mem_info[core_id];
+ if ((mem_info->id == core_id) && (mem_info->vbase[0] != NULL))
+ return true;
+
+ return false;
+}
+
+/*
+ * imc_mem_init : Function to support memory allocation for core imc.
+ */
+static int imc_mem_init(struct imc_pmu *pmu_ptr)
+{
The function placement is horrible. This function belongs to the pmu init
stuff and wants to be placed there and not five pages away in the middle of
unrelated functions.
+ int nr_cores;
+
+ if (pmu_ptr->imc_counter_mmaped)
+ return 0;
+ nr_cores = num_present_cpus() / threads_per_core;
+ pmu_ptr->mem_info = kzalloc((sizeof(struct imc_mem_info) * nr_cores),
GFP_KERNEL);
+ if (!pmu_ptr->mem_info)
+ return -ENOMEM;
+ return 0;
+}
+static int core_imc_event_init(struct perf_event *event)
+{
+ int core_id, rc;
+ u64 config = event->attr.config;
+ struct imc_mem_info *pcmi;
+ struct imc_pmu *pmu;
+
+ if (event->attr.type != event->pmu->type)
+ return -ENOENT;
+
+ /* Sampling not supported */
+ if (event->hw.sample_period)
+ return -EINVAL;
+
+ /* unsupported modes and filters */
+ if (event->attr.exclude_user ||
+ event->attr.exclude_kernel ||
+ event->attr.exclude_hv ||
+ event->attr.exclude_idle ||
+ event->attr.exclude_host ||
+ event->attr.exclude_guest)
+ return -EINVAL;
+
+ if (event->cpu < 0)
+ return -EINVAL;
+
+ event->hw.idx = -1;
+ pmu = imc_event_to_pmu(event);
+
+ /* Sanity check for config (event offset and rvalue) */
+ if (((config & IMC_EVENT_OFFSET_MASK) > pmu->counter_mem_size) ||
+ ((config & IMC_EVENT_RVALUE_MASK) != 0))
+ return -EINVAL;
+
+ if (!is_core_imc_mem_inited(event->cpu))
+ return -ENODEV;
+
+ core_id = event->cpu / threads_per_core;
+ pcmi = &pmu->mem_info[core_id];
+ if ((pcmi->id != core_id) || (!pcmi->vbase[0]))
+ return -ENODEV;
+
+ event->hw.event_base = (u64)pcmi->vbase[0] + (config &
IMC_EVENT_OFFSET_MASK);
+ /*
+ * Core pmu units are enabled only when it is used.
+ * See if this is triggered for the first time.
+ * If yes, take the mutex lock and enable the core counters.
+ * If not, just increment the count in core_events.
+ */
+ if (atomic_inc_return(&core_events[core_id]) == 1) {
+ mutex_lock(&imc_core_reserve);
+ rc = opal_imc_counters_start(OPAL_IMC_COUNTERS_CORE,
+
get_hard_smp_processor_id(event->cpu));
+ mutex_unlock(&imc_core_reserve);
Idea is to handle multiple event session for a given core and
yes, my bad, current implementation is racy/broken.
But an alternate approach is to have a per-core mutex and
per-core ref count to handle this.
event_init path:
per-core mutex lock
if ( per-core[refcount] == 0) {
rc = opal call to start the engine;
if (rc on failure) {
per-core mutex unlock;
log error info;
return error;
}
}
increment the per-core[refcount];
per-core mutex unlock;
event_destroy path:
per-core mutex lock
decrement the per-core[refcount];
if ( per-core[refcount] == 0) {
rc = opal call to stop the engine;
if (rc on failure) {
per-core mutex unlock;
log the failure;
return error;
}
} else if ( per-core[refcount] < 0) {
WARN()
per-core[refcount] = 0;
}
per-core mutext unlock;
Kindly let me know your comment for this.
Maddy
That machinery here is racy as hell in several aspects.
CPU0 CPU1
atomic_inc_ret(core_events[0]) -> 1
preemption()
atomic_inc_ret(core_events[0]) -> 2
return 0;
Uses the event, without counters
being started until the preempted
task comes on the CPU again.
Here is another one:
CPU0 CPU1
atomic_dec_ret(core_events[0]) -> 0
atomic_inc_ret(core_events[1] -> 1
mutex_lock();
mutex_lock() start counter();
mutex_unlock()
stop_counter();
mutex_unlock();
Yay, another stale event!
Brilliant stuff that, or maybe not so much.
+ if (rc) {
+ atomic_dec_return(&core_events[core_id]);
What's the point of using atomic_dec_return here if you ignore the return
value? Not that it matters much as the whole logic is crap anyway.
+ pr_err("IMC: Unable to start the counters for core
%d\n", core_id);
+ return -ENODEV;
+ }
+ }
@@ -410,22 +658,38 @@ int init_imc_pmu(struct imc_events *events, int idx,
struct imc_pmu *pmu_ptr)
{
int ret = -ENODEV;
+
Sure ret needs to stay initialized, just in case imc_mem_init() does not
return anything magically, right?
+ ret = imc_mem_init(pmu_ptr);
+ if (ret)
+ goto err_free;
/* Add cpumask and register for hotplug notification */
- if (atomic_inc_return(&nest_pmus) == 1) {
- /*
- * Nest imc pmu need only one cpu per chip, we initialize the
- * cpumask for the first nest imc pmu and use the same for the
rest.
- * To handle the cpuhotplug callback unregister, we track
- * the number of nest pmus registers in "nest_pmus".
- * "nest_imc_cpumask_initialized" is set to zero during
cpuhotplug
- * callback unregister.
- */
- ret = nest_pmu_cpumask_init();
+ switch (pmu_ptr->domain) {
+ case IMC_DOMAIN_NEST:
+ if (atomic_inc_return(&nest_pmus) == 1) {
+ /*
+ * Nest imc pmu need only one cpu per chip, we
initialize
+ * the cpumask for the first nest imc pmu and use the
+ * same for the rest.
+ * To handle the cpuhotplug callback unregister, we
track
+ * the number of nest pmus registers in "nest_pmus".
+ * "nest_imc_cpumask_initialized" is set to zero during
+ * cpuhotplug callback unregister.
+ */
+ ret = nest_pmu_cpumask_init();
+ if (ret)
+ goto err_free;
+ mutex_lock(&imc_nest_inited_reserve);
+ nest_imc_cpumask_initialized = 1;
+ mutex_unlock(&imc_nest_inited_reserve);
+ }
+ break;
+ case IMC_DOMAIN_CORE:
+ ret = core_imc_pmu_cpumask_init();
if (ret)
- goto err_free;
- mutex_lock(&imc_nest_inited_reserve);
- nest_imc_cpumask_initialized = 1;
- mutex_unlock(&imc_nest_inited_reserve);
+ return ret;
Oh, so now you replaced the goto with ret. What is actually taking care of
the cleanup if that fails?
+ break;
+ default:
+ return -1; /* Unknown domain */
}
ret = update_events_in_group(events, idx, pmu_ptr);
if (ret)
@@ -459,5 +723,10 @@ int init_imc_pmu(struct imc_events *events, int idx,
mutex_unlock(&imc_nest_inited_reserve);
}
}
+ /* For core_imc, we have allocated memory, we need to free it */
+ if (pmu_ptr->domain == IMC_DOMAIN_CORE) {
+ cleanup_all_core_imc_memory(pmu_ptr);
+ cpuhp_remove_state(CPUHP_AP_PERF_POWERPC_CORE_IMC_ONLINE);
Cute. You cleanuo the memory stuff and then you let the hotplug core invoke
the offline callbacks which then deal with freed memory.
Thanks,
tglx
