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Add missing mutex when reading from shared variable bg_bottom_compaction_scheduled_, bg_compaction_scheduled_ #10610

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Add missing mutex when reading from shared variable bg_bottom_compaction_scheduled_, bg_compaction_scheduled_ #10610

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df954a2
Added missing mutex when reading shared variable
hx235 Aug 30, 2022
3f5cc5d
Use InstrumentedMutexLock as much as possible
hx235 Aug 30, 2022
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4 changes: 3 additions & 1 deletion db/compaction/compaction_job.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -321,6 +321,7 @@ void CompactionJob::AcquireSubcompactionResources(
->write_controller()
->NeedSpeedupCompaction())
.max_compactions;
db_mutex_->Lock();
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Maybe use InstrumentedMutexLock

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Fixed.

// Apply min function first since We need to compute the extra subcompaction
// against compaction limits. And then try to reserve threads for extra
// subcompactions. The actual number of reserved threads could be less than
Expand All @@ -329,7 +330,6 @@ void CompactionJob::AcquireSubcompactionResources(
std::max(max_db_compactions - *bg_compaction_scheduled_ -
*bg_bottom_compaction_scheduled_,
0);
db_mutex_->Lock();
// Reservation only supports backgrdoun threads of which the priority is
// between BOTTOM and HIGH. Need to degrade the priority to HIGH if the
// origin thread_pri_ is higher than that. Similar to ReleaseThreads().
Expand Down Expand Up @@ -380,6 +380,7 @@ void CompactionJob::ReleaseSubcompactionResources() {
if (extra_num_subcompaction_threads_reserved_ == 0) {
return;
}
db_mutex_->Lock();
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Ditto

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Unfortunately I can't easily do InstrumentedMutexLock for this one cuz the function right after its unlock "ShrinkSubcompactionResources(extra_num_subcompaction_threads_reserved_);" but before the scope ends need to acquire lock again. So I won't be fixing this one.

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@riversand963 riversand963 Aug 30, 2022 •
edited
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How about

{
  InstrumentedMutexLock (db_mutex_);
  assert(...)
}
ShrinkSubcompactionresrouce();

Furthermore, mutex lock-unlock is not needed if in opt mode, but if we differentiate between debug and opt mode, there may be a gap in test coverage, thus I am fine with current.

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Got you - yeah I can change to your suggested version! This is the easy way that I didn't think of!

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Fixed

// The number of reserved threads becomes larger than 0 only if the
// compaction prioity is round robin and there is no sufficient
// sub-compactions available
Expand All @@ -391,6 +392,7 @@ void CompactionJob::ReleaseSubcompactionResources() {
1 + extra_num_subcompaction_threads_reserved_ ||
*bg_compaction_scheduled_ >=
1 + extra_num_subcompaction_threads_reserved_);
db_mutex_->Unlock();
ShrinkSubcompactionResources(extra_num_subcompaction_threads_reserved_);
}

Expand Down