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MTVU: hide ring buffer pointer bug under the carpet 

There is a bug lurking around (intro of SotC). Unfortunately, I didn't find it. So instead, I added a safety net
in the ring buffer reservation.
This commit is contained in:
Gregory Hainaut 2017-01-22 15:42:14 +01:00
parent 81adc3ef4d
commit 44b5552231
1 changed files with 7 additions and 2 deletions
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9
pcsx2/MTVU.cpp
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@ -166,10 +166,14 @@ __ri void VU_Thread::WaitOnSize(s32 size)
for(;;) { for(;;) {
s32 readPos = GetReadPos(); s32 readPos = GetReadPos();
if (readPos <= m_write_pos) break; // MTVU is reading in back of write_pos if (readPos <= m_write_pos) break; // MTVU is reading in back of write_pos
if (readPos > m_write_pos + size) break; // Enough free front space // FIXME greg: there is a bug somewhere in the queue pointer
// management. It creates a deadlock/corruption in SotC intro (before
// the first menu). I added a 4KB safety net which seem to avoid to
// trigger the bug.
// Note: a wait lock instead of a yield also helps to avoid the bug.
if (readPos > m_write_pos + size + _4kb) break; // Enough free front space
{ // Let MTVU run to free up buffer space { // Let MTVU run to free up buffer space
KickStart(); KickStart();
if (IsDevBuild) DevCon.WriteLn("WaitOnSize()");
// Locking might trigger a full flush of the ring buffer. Yield // Locking might trigger a full flush of the ring buffer. Yield
// will be more aggressive, and only flush the minimal size. // will be more aggressive, and only flush the minimal size.
// Performance will be smoother but it will consume extra CPU cycle // Performance will be smoother but it will consume extra CPU cycle
@ -260,6 +264,7 @@ __fi void VU_Thread::Write(u32 val)
GetWritePtr()[0] = val; GetWritePtr()[0] = val;
m_write_pos += 1; m_write_pos += 1;
} }
__fi void VU_Thread::Write(void* src, u32 size) __fi void VU_Thread::Write(void* src, u32 size)
{ {
memcpy(GetWritePtr(), src, size); memcpy(GetWritePtr(), src, size);