Ceph » RADOS

discover from https://github.com/ceph/ceph/pull/58302

**unittest_mclock_scheduler**  failed at here,  while 1 dead loop:

In unittest_mclock_scheduler, 
- multiple test cases use the same logger ADDR (ptr)
- and add it to the logger collection of the same g_ceph_context cct
- Caused a dead loop
- I finally understood why perfcounter is hardly used in src/test

Solution:
- I don't think it's mclock's fault.
- I think it's a problem with perfcounter itself (add/remove...)
- This PR does not introduce this issue, It should be introduced by e9ecd1b38447  @sseshasa 
- So I added ignore_perfcounter=true parameter to TEST

https://github.com/ceph/ceph/blob/main/src/common/perf_counters.cc#L41

```
void PerfCountersCollectionImpl::add(PerfCounters *l)
{
  // make sure the name is unique
  perf_counters_set_t::iterator i;
  i = m_loggers.find(l);  //ptr1
  while (i != m_loggers.end()) {  // dead loop here
    ostringstream ss;
    ss << l->get_name() << "-" << (void*)l;
    l->set_name(ss.str());
    i = m_loggers.find(l); //ptr1=ptr1,  cannot be m_loggers.end()
  }

  m_loggers.insert(l);
  ... ...
}
```

https://github.com/ceph/ceph/blob/main/src/common/perf_counters.h#L359
https://github.com/ceph/ceph/blob/main/src/common/perf_counters.h#L312

```
class SortPerfCountersByName {
public:
  bool operator()(const PerfCounters* lhs, const PerfCounters* rhs) const {
    return (lhs->get_name() < rhs->get_name());
  }
};

typedef std::set <PerfCounters*, SortPerfCountersByName> perf_counters_set_t; ///ptr set

//PerfCountersCollectionImpl
  perf_counters_set_t m_loggers;
```

```
[----------] 5 tests from mClockSchedulerTest
[ RUN      ] mClockSchedulerTest.TestEmpty
_init_logger zhangjianwei2 mclock-shard-queue-0
_init_logger zhangjianwei2 logger=0x5610ac84e0a0  //same addr (ptr)
add zhangjianwei2 111111
add zhangjianwei2 121111 l=0x5610ac84e0a0          //first time add to logger collection
add zhangjianwei2 131111
add zhangjianwei2 141111
add zhangjianwei2 151111
_init_logger zhangjianwei2 add logger=0x5610ac84e0a0  
[       OK ] mClockSchedulerTest.TestEmpty (0 ms)
[ RUN      ] mClockSchedulerTest.TestSingleClientOrderedEnqueueDequeue
_init_logger zhangjianwei2 mclock-shard-queue-0
_init_logger zhangjianwei2 logger=0x5610ac84e0a0   //same addr (ptr)
add zhangjianwei2 111111                                            //PerfCountersCollectionImpl::add
add zhangjianwei2 121111 l=0x5610ac84e0a0           //second time add to logger collection, dead loop here 
add zhangjianwei2 120111 l=0x5610ac84e0a0 mclock-shard-queue-0-0x5610ac84e0a0
add zhangjianwei2 120211 l=0x5610ac84e0a0 mclock-shard-queue-0-0x5610ac84e0a0
add zhangjianwei2 120111 l=0x5610ac84e0a0 mclock-shard-queue-0-0x5610ac84e0a0-0x5610ac84e0a0
add zhangjianwei2 120211 l=0x5610ac84e0a0 mclock-shard-queue-0-0x5610ac84e0a0-0x5610ac84e0a0
add zhangjianwei2 120111 l=0x5610ac84e0a0 mclock-shard-queue-0-0x5610ac84e0a0-0x5610ac84e0a0-0x5610ac84e0a0
add zhangjianwei2 120211 l=0x5610ac84e0a0 mclock-shard-queue-0-0x5610ac84e0a0-0x5610ac84e0a0-0x5610ac84e0a0
add zhangjianwei2 120111 l=0x5610ac84e0a0 mclock-shard-queue-0-0x5610ac84e0a0-0x5610ac84e0a0-0x5610ac84e0a0-0x5610ac84e0a0
```