LizardByte / LizardByte/Sunshine

Potential deadlocks due to thread_safe pop() with infinite wait

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Description

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your issue described in the documentation?

- [x] I have read the documentation

### Is your issue present in the latest beta/pre-release?

This issue is present in the latest pre-release

### Describe the Bug

To fix #5249 an issue with unbounded (infinitely waiting) `pop()` was discovered and fixed to stop streams freezing in a `while(peek()) { pop() }` to drain images. The same pattern is also used in other parts of the code that should be checked for potential deadlocks due to waiting infinitely and corrected if possible.

The [codeparts](https://github.com/LizardByte/Sunshine/pull/5249#issuecomment-4796712749) identified using a similar pattern are:
```
$ git grep -nC1 "pop()" | grep -C1 "peek()"
--
src/input.cpp-463- if (touch_port_event->peek()) {
src/input.cpp:464: touch_port = *touch_port_event->pop();
--
--
src/stream.cpp-1117- while (feedback_queue->peek()) {
src/stream.cpp:1118: auto feedback_msg = feedback_queue->pop();
--
--
src/stream.cpp-1124- while (session->control.peer && hdr_queue->peek()) {
src/stream.cpp:1125: auto hdr_info = hdr_queue->pop();
--
--
src/stream.cpp-1197- while (message_queue_queue->peek()) {
src/stream.cpp:1198: auto message_queue_opt = message_queue_queue->pop();
--
src/stream.cpp:1297: while (auto packet = packets->pop()) {
src/stream.cpp-1298- if (shutdown_event->peek()) {
--
--
src/stream.cpp:1620: while (auto packet = packets->pop()) {
src/stream.cpp-1621- if (shutdown_event->peek()) {
--
--
--
src/video.cpp-1420- while (capture_ctx_queue->peek()) {
src/video.cpp:1421: capture_ctxs.emplace_back(std::move(*capture_ctx_queue->pop()));
--
--
src/video.cpp-1482- if (switch_display_event->peek()) {
src/video.cpp:1483: display_p = std::clamp(*switch_display_event->pop(), 0, (int) display_names.size() - 1);
--
--
src/video.cpp-2302- if (switch_display_event->peek()) {
src/video.cpp:2303: display_p = std::clamp(*switch_display_event->pop(), 0, (int) display_names.size() - 1);
--
--
src/video.cpp-2335- while (encode_session_ctx_queue.peek()) {
src/video.cpp:2336: auto encode_session_ctx = encode_session_ctx_queue.pop();
--
tests/unit/test_audio.cpp:55: while (const auto packet = packets->pop()) {
tests/unit/test_audio.cpp-56- if (shutdown_event->peek()) {
--
tests/unit/test_http_pairing.cpp-118- ASSERT_EQ(add_cert->peek(), true);
tests/unit/test_http_pairing.cpp:119: auto cert = add_cert->pop();
```

### Expected Behavior

_No response_

### Additional Context

_No response_

### Host Operating System

other, n/a

### Operating System Version

n/a

### Architecture

amd64/x86_64

### Package

n/a

### GPU Type

n/a

### GPU Model

n/a

### GPU Driver/Mesa Version

n/a

### Capture Method

None

### Apps

```json

```

### Log output

```shell

```

### Online logs

_No response_

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the pop()/peek() locations listed in src/input.cpp, src/stream.cpp, src/video.cpp, tests/unit/test_audio.cpp, and tests/unit/test_http_pairing.cpp, then compare them with the fix for #5249. Check each pattern for an unbounded wait and update the affected code where appropriate; run the relevant unit tests and confirm stream draining no longer risks deadlock.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
backend
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
48/100

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