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DVDThread: Remove s_dvd_thread_done_working and fix race condition

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s_dvd_thread_done_working makes the logic more complicated,
and degasus pointed out a race condition that can happen if
the CPU thread calls WaitForIdle right in between the DVD
thread executing done_working.Set() and done_working.Reset()
while there is work left to do. To avoid this, let's just get
rid of s_dvd_thread_done_working. It's a relic from the old
DVDThread design. Thanks to the last few commits, WaitUntilIdle
only gets called rarely (disc change and savestate), so it's
not a problem if WaitUntilIdle ends up being slower.
This commit is contained in:
JosJuice 2016-10-15 13:57:56 +02:00
parent f1879cc356
commit e1f6ab5592
1 changed files with 24 additions and 14 deletions
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38
Source/Core/Core/HW/DVDThread.cpp
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@ -56,6 +56,9 @@ struct ReadRequest
using ReadResult = std::pair<ReadRequest, std::vector<u8>>;
static void StartDVDThread();
static void StopDVDThread();
static void DVDThread();
static void StartReadInternal(bool copy_to_ram, u32 output_address, u64 dvd_offset, u32 length,
@ -70,7 +73,6 @@ static u64 s_next_id = 0;
static std::thread s_dvd_thread;
static Common::Event s_request_queue_expanded; // Is set by CPU thread
static Common::Event s_result_queue_expanded; // Is set by DVD thread
static Common::Event s_dvd_thread_done_working; // Is set by DVD thread
static Common::Flag s_dvd_thread_exiting(false); // Is set by CPU thread
static Common::FifoQueue<ReadRequest, false> s_request_queue;
@ -81,7 +83,6 @@ void Start()
{
s_finish_read = CoreTiming::RegisterEvent("FinishReadDVDThread", FinishRead);
s_dvd_thread_exiting.Clear();
s_request_queue_expanded.Reset();
s_result_queue_expanded.Reset();
s_request_queue.Clear();
@ -91,11 +92,22 @@ void Start()
// much, because this will never get exposed to the emulated game.
s_next_id = 0;
StartDVDThread();
}
static void StartDVDThread()
{
_assert_(!s_dvd_thread.joinable());
s_dvd_thread_exiting.Clear();
s_dvd_thread = std::thread(DVDThread);
}
void Stop()
{
StopDVDThread();
}
static void StopDVDThread()
{
_assert_(s_dvd_thread.joinable());
@ -131,6 +143,9 @@ void DoState(PointerWrap& p)
// TODO: Savestates can be smaller if the buffers of results aren't saved,
// but instead get re-read from the disc when loading the savestate.
// TODO: It would be possible to create a savestate faster by stopping
// the DVD thread regardless of whether there are pending requests.
// After loading a savestate, the debug log in FinishRead will report
// screwed up times for requests that were submitted before the savestate
// was made. Handling that properly may be more effort than it's worth.
@ -140,13 +155,11 @@ void WaitUntilIdle()
{
_assert_(Core::IsCPUThread());
// Wait until DVD thread isn't working
s_dvd_thread_done_working.Wait();
while (!s_request_queue.Empty())
s_result_queue_expanded.Wait();
// Set the event again so that we still know that the DVD thread
// isn't working. This is needed in case this function gets called
// again before the DVD thread starts working.
s_dvd_thread_done_working.Set();
StopDVDThread();
StartDVDThread();
}
void StartRead(u64 dvd_offset, u32 length, bool decrypt, DVDInterface::ReplyType reply_type,
@ -162,8 +175,9 @@ void StartReadToEmulatedRAM(u32 output_address, u64 dvd_offset, u32 length, bool
ticks_until_completion);
}
void StartReadInternal(bool copy_to_ram, u32 output_address, u64 dvd_offset, u32 length,
bool decrypt, DVDInterface::ReplyType reply_type, s64 ticks_until_completion)
static void StartReadInternal(bool copy_to_ram, u32 output_address, u64 dvd_offset, u32 length,
bool decrypt, DVDInterface::ReplyType reply_type,
s64 ticks_until_completion)
{
_assert_(Core::IsCPUThread());
@ -255,15 +269,11 @@ static void DVDThread()
while (true)
{
s_dvd_thread_done_working.Set();
s_request_queue_expanded.Wait();
if (s_dvd_thread_exiting.IsSet())
return;
s_dvd_thread_done_working.Reset();
ReadRequest request;
while (s_request_queue.Pop(request))
{