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Fix race conditions in NotePlayHandleManager (#4966)

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NotePlayHandleManager::acquire uses a read lock unless the pool is empty.
If two threads try to acquire NotePlayHandle simultaneously
when the value of s_availableIndex is 1, one thread will try to read s_available[-1].
If the acquire action and the release action are done at the same time,
NotePlayHandleManager::acquire may try to read data
before NotePlayHandleManager::release actually writes.

This commit prevents them by always using the write lock when acquiring a NotePlayHandle.
This commit is contained in:
Hyunjin Song
2019-05-08 15:12:17 +09:00
committed by GitHub
parent 3dcffbf96f
commit b9503a8c70
1 changed files with 3 additions and 7 deletions
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10
src/core/NotePlayHandle.cpp
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@@ -577,13 +577,9 @@ NotePlayHandle * NotePlayHandleManager::acquire( InstrumentTrack* instrumentTrac
int midiEventChannel,
NotePlayHandle::Origin origin )
{
if( s_availableIndex < 0 )
{
s_mutex.lockForWrite();
if( s_availableIndex < 0 ) extend( NPH_CACHE_INCREMENT );
s_mutex.unlock();
}
s_mutex.lockForRead();
// TODO: use some lockless data structures
s_mutex.lockForWrite();
if (s_availableIndex < 0) { extend(NPH_CACHE_INCREMENT); }
NotePlayHandle * nph = s_available[ s_availableIndex.fetchAndAddOrdered( -1 ) ];
s_mutex.unlock();