DFG::Plan shouldn't read from its VM once it's been cancelled
[WebKit-https.git] / Source / JavaScriptCore / dfg / DFGSafepoint.cpp
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25
26 #include "config.h"
27 #include "DFGSafepoint.h"
28
29 #if ENABLE(DFG_JIT)
30
31 #include "DFGPlan.h"
32 #include "DFGScannable.h"
33 #include "DFGThreadData.h"
34 #include "JSCInlines.h"
35
36 namespace JSC { namespace DFG {
37
38 Safepoint::Result::~Result()
39 {
40     RELEASE_ASSERT(m_wasChecked);
41 }
42
43 bool Safepoint::Result::didGetCancelled()
44 {
45     m_wasChecked = true;
46     return m_didGetCancelled;
47 }
48
49 Safepoint::Safepoint(Plan& plan, Result& result)
50     : m_vm(plan.vm)
51     , m_plan(plan)
52     , m_didCallBegin(false)
53     , m_result(result)
54 {
55     RELEASE_ASSERT(result.m_wasChecked);
56     result.m_wasChecked = false;
57     result.m_didGetCancelled = false;
58 }
59
60 Safepoint::~Safepoint()
61 {
62     RELEASE_ASSERT(m_didCallBegin);
63     if (ThreadData* data = m_plan.threadData) {
64         RELEASE_ASSERT(data->m_safepoint == this);
65         data->m_rightToRun.lock();
66         data->m_safepoint = nullptr;
67     }
68 }
69
70 void Safepoint::add(Scannable* scannable)
71 {
72     RELEASE_ASSERT(!m_didCallBegin);
73     m_scannables.append(scannable);
74 }
75
76 void Safepoint::begin()
77 {
78     RELEASE_ASSERT(!m_didCallBegin);
79     m_didCallBegin = true;
80     if (ThreadData* data = m_plan.threadData) {
81         RELEASE_ASSERT(!data->m_safepoint);
82         data->m_safepoint = this;
83         data->m_rightToRun.unlock();
84     }
85 }
86
87 void Safepoint::checkLivenessAndVisitChildren(SlotVisitor& visitor)
88 {
89     RELEASE_ASSERT(m_didCallBegin);
90
91     if (m_result.m_didGetCancelled)
92         return; // We were cancelled during a previous GC!
93     
94     if (!isKnownToBeLiveDuringGC())
95         return;
96     
97     for (unsigned i = m_scannables.size(); i--;)
98         m_scannables[i]->visitChildren(visitor);
99 }
100
101 bool Safepoint::isKnownToBeLiveDuringGC()
102 {
103     RELEASE_ASSERT(m_didCallBegin);
104     
105     if (m_result.m_didGetCancelled)
106         return true; // We were cancelled during a previous GC, so let's not mess with it this time around - pretend it's live and move on.
107     
108     return m_plan.isKnownToBeLiveDuringGC();
109 }
110
111 void Safepoint::cancel()
112 {
113     RELEASE_ASSERT(m_didCallBegin);
114     RELEASE_ASSERT(!m_result.m_didGetCancelled); // We cannot get cancelled twice because subsequent GCs will think that we're alive and they will not do anything to us.
115     
116     m_plan.cancel();
117     m_result.m_didGetCancelled = true;
118     m_vm = nullptr;
119 }
120
121 VM* Safepoint::vm() const
122 {
123     return m_vm;
124 }
125
126 } } // namespace JSC::DFG
127
128 #endif // ENABLE(DFG_JIT)
129