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src: limit foreground tasks draining loop · nodejs/node@6bf816f · GitHub

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Commit 6bf816f

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ulan
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MylesBorins
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src: limit foreground tasks draining loop
Foreground tasks that repost themselves can force the draining loop to run indefinitely long without giving other tasks chance to run. This limits the foreground task draining loop to run only the tasks that were in the tasks queue at the beginning of the loop. PR-URL: #19987 Fixes: #19937 Reviewed-By: Anna Henningsen <anna@addaleax.net> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Yang Guo <yangguo@chromium.org> Reviewed-By: Colin Ihrig <cjihrig@gmail.com> Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com> Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Anatoli Papirovski <apapirovski@mac.com> Reviewed-By: Khaidi Chu <i@2333.moe>
1 parent 99e0b91 commit 6bf816f

5 files changed

Lines changed: 83 additions & 7 deletions

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‎node.gyp‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -961,6 +961,7 @@
961961
'test/cctest/test_base64.cc',
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'test/cctest/test_node_postmortem_metadata.cc',
963963
'test/cctest/test_environment.cc',
964+
'test/cctest/test_platform.cc',
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'test/cctest/test_util.cc',
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'test/cctest/test_url.cc'
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],

‎src/inspector_agent.cc‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -316,7 +316,7 @@ class NodeInspectorClient : public V8InspectorClient {
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terminated_ = false;
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running_nested_loop_ = true;
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while (!terminated_ && channel_->waitForFrontendMessage()) {
319-
platform_->FlushForegroundTasks(env_->isolate());
319+
while (platform_->FlushForegroundTasks(env_->isolate())) {}
320320
}
321321
terminated_ = false;
322322
running_nested_loop_ = false;

‎src/node_platform.cc‎

Lines changed: 18 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -95,7 +95,7 @@ void PerIsolatePlatformData::PostDelayedTask(
9595
}
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9797
PerIsolatePlatformData::~PerIsolatePlatformData() {
98-
FlushForegroundTasksInternal();
98+
while (FlushForegroundTasksInternal()) {}
9999
CancelPendingDelayedTasks();
100100

101101
uv_close(reinterpret_cast<uv_handle_t*>(flush_tasks_),
@@ -223,7 +223,13 @@ bool PerIsolatePlatformData::FlushForegroundTasksInternal() {
223223
});
224224
});
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}
226-
while (std::unique_ptr<Task> task = foreground_tasks_.Pop()) {
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// Move all foreground tasks into a separate queue and flush that queue.
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// This way tasks that are posted while flushing the queue will be run on the
228+
// next call of FlushForegroundTasksInternal.
229+
std::queue<std::unique_ptr<Task>> tasks = foreground_tasks_.PopAll();
230+
while (!tasks.empty()) {
231+
std::unique_ptr<Task> task = std::move(tasks.front());
232+
tasks.pop();
227233
did_work = true;
228234
RunForegroundTask(std::move(task));
229235
}
@@ -254,8 +260,8 @@ void NodePlatform::CallDelayedOnForegroundThread(Isolate* isolate,
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std::unique_ptr<Task>(task), delay_in_seconds);
255261
}
256262

257-
void NodePlatform::FlushForegroundTasks(v8::Isolate* isolate) {
258-
ForIsolate(isolate)->FlushForegroundTasksInternal();
263+
bool NodePlatform::FlushForegroundTasks(v8::Isolate* isolate) {
264+
return ForIsolate(isolate)->FlushForegroundTasksInternal();
259265
}
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261267
void NodePlatform::CancelPendingDelayedTasks(v8::Isolate* isolate) {
@@ -348,4 +354,12 @@ void TaskQueue<T>::Stop() {
348354
tasks_available_.Broadcast(scoped_lock);
349355
}
350356

357+
template <class T>
358+
std::queue<std::unique_ptr<T>> TaskQueue<T>::PopAll() {
359+
Mutex::ScopedLock scoped_lock(lock_);
360+
std::queue<std::unique_ptr<T>> result;
361+
result.swap(task_queue_);
362+
return result;
363+
}
364+
351365
} // namespace node

‎src/node_platform.h‎

Lines changed: 8 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -26,6 +26,7 @@ class TaskQueue {
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void Push(std::unique_ptr<T> task);
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std::unique_ptr<T> Pop();
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std::unique_ptr<T> BlockingPop();
29+
std::queue<std::unique_ptr<T>> PopAll();
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void NotifyOfCompletion();
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void BlockingDrain();
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void Stop();
@@ -65,7 +66,9 @@ class PerIsolatePlatformData :
6566
void ref();
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int unref();
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68-
// Returns true iff work was dispatched or executed.
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// Returns true if work was dispatched or executed. New tasks that are
70+
// posted during flushing of the queue are postponed until the next
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// flushing.
6972
bool FlushForegroundTasksInternal();
7073
void CancelPendingDelayedTasks();
7174

@@ -130,7 +133,10 @@ class NodePlatform : public MultiIsolatePlatform {
130133
double CurrentClockTimeMillis() override;
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v8::TracingController* GetTracingController() override;
132135

133-
void FlushForegroundTasks(v8::Isolate* isolate);
136+
// Returns true if work was dispatched or executed. New tasks that are
137+
// posted during flushing of the queue are postponed until the next
138+
// flushing.
139+
bool FlushForegroundTasks(v8::Isolate* isolate);
134140

135141
void RegisterIsolate(IsolateData* isolate_data, uv_loop_t* loop) override;
136142
void UnregisterIsolate(IsolateData* isolate_data) override;

‎test/cctest/test_platform.cc‎

Lines changed: 55 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,55 @@
1+
#include "node_internals.h"
2+
#include "libplatform/libplatform.h"
3+
4+
#include <string>
5+
#include "gtest/gtest.h"
6+
#include "node_test_fixture.h"
7+
8+
// This task increments the given run counter and reposts itself until the
9+
// repost counter reaches zero.
10+
class RepostingTask : public v8::Task {
11+
public:
12+
explicit RepostingTask(int repost_count,
13+
int* run_count,
14+
v8::Isolate* isolate,
15+
node::NodePlatform* platform)
16+
: repost_count_(repost_count),
17+
run_count_(run_count),
18+
isolate_(isolate),
19+
platform_(platform) {}
20+
21+
// v8::Task implementation
22+
void Run() final {
23+
++*run_count_;
24+
if (repost_count_ > 0) {
25+
--repost_count_;
26+
platform_->CallOnForegroundThread(isolate_,
27+
new RepostingTask(repost_count_, run_count_, isolate_, platform_));
28+
}
29+
}
30+
31+
private:
32+
int repost_count_;
33+
int* run_count_;
34+
v8::Isolate* isolate_;
35+
node::NodePlatform* platform_;
36+
};
37+
38+
class PlatformTest : public EnvironmentTestFixture {};
39+
40+
TEST_F(PlatformTest, SkipNewTasksInFlushForegroundTasks) {
41+
v8::Isolate::Scope isolate_scope(isolate_);
42+
const v8::HandleScope handle_scope(isolate_);
43+
const Argv argv;
44+
Env env {handle_scope, argv};
45+
int run_count = 0;
46+
platform->CallOnForegroundThread(
47+
isolate_, new RepostingTask(2, &run_count, isolate_, platform.get()));
48+
EXPECT_TRUE(platform->FlushForegroundTasks(isolate_));
49+
EXPECT_EQ(1, run_count);
50+
EXPECT_TRUE(platform->FlushForegroundTasks(isolate_));
51+
EXPECT_EQ(2, run_count);
52+
EXPECT_TRUE(platform->FlushForegroundTasks(isolate_));
53+
EXPECT_EQ(3, run_count);
54+
EXPECT_FALSE(platform->FlushForegroundTasks(isolate_));
55+
}

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