Fix MPV Segfaults: Vulkan Layer & MangoHud Crashes

Hey guys, ever been in that super frustrating situation where you're just trying to kick back and watch some awesome content with mpv, maybe even keeping an eye on your system performance with MangoHud, only for it to crash right at startup? Yeah, it's a real bummer, and it often points to some tricky interactions, especially when the Vulkan layer gets involved. We're talking about those dreaded mpv segfaults that can stop your media playback dead in its tracks before it even begins. It's a common pain point for many Linux users, particularly those rocking dual-GPU setups or specific driver configurations. Today, we're going to dive deep into understanding why these startup crashes happen, focusing on the combination of MangoHud and Vulkan in mpv, and more importantly, how you can troubleshoot and potentially fix them. So, let's get into it and make sure your media player runs smoothly!

Unpacking the MPV and MangoHud Segfault Mystery

Alright, let's talk about the main culprit here: mpv often experiencing a segfault immediately after startup, especially when you've got MangoHud enabled. This isn't just a minor glitch; a segfault (or segmentation fault) means the program tried to access a memory location it wasn't allowed to, leading to an abrupt and complete crash. It's like the program tripped over its own feet and couldn't recover, guys. When this happens with mpv and MangoHud, it suggests a deeper conflict in how these two powerful tools are interacting, particularly concerning graphical resources managed by the Vulkan layer. This issue can be incredibly frustrating because it prevents you from even getting to the point of playing a video, making your media player essentially unusable with the overlay active.

Our specific scenario involves a user on Arch Linux running MangoHud 0.8.2-2, which is a fairly recent, but not the absolute latest, version from the Arch repositories. The hardware setup is quite interesting too: an Intel(R) Graphics (RPL-S) (Mesa 25.3.1) integrated GPU paired with a powerful NVIDIA GeForce RTX 4080 Laptop GPU (580.105.08). This dual-GPU environment is often where such issues become more pronounced, as applications and layers need to correctly identify and utilize the right graphics hardware and its corresponding drivers. The problem is consistently reproducible by simply running the command MANGOHUD=1 mpv. Instead of launching and displaying its interface or starting video playback, mpv just crashes. This directly contradicts the expected behavior, which is for mpv to launch normally and either play a file or display usage instructions if no file is provided. The fact that the issue is so easily triggered by enabling MangoHud points fingers directly at the interaction between the overlay and mpv's initialization process, particularly with the Vulkan layer active. Understanding these details is crucial for diagnosing and resolving these pesky mpv startup crashes and getting back to seamless media enjoyment.

The core of the problem often lies in how MangoHud tries to hook into the Vulkan API calls that mpv makes during its startup sequence. When mpv initializes its Vulkan context, it's essentially setting up the pipeline for rendering video. If MangoHud tries to inject its overlay or query certain GPU metrics at precisely the wrong moment, or if there's an incompatibility in how it handles the Vulkan layer with specific drivers (like Mesa for Intel or NVIDIA's proprietary drivers), a segfault can occur. The crash might be related to memory allocation, improper resource management, or even a race condition where mpv and MangoHud are trying to access or modify the same critical data simultaneously during initialization. This is a classic concurrency bug, and they are notoriously difficult to track down. The fact that older MangoHud versions are explicitly not supported for bug reports also highlights that these issues are often ironed out in newer releases, making a version check incredibly important. For those of us using Linux for gaming and media, having robust overlay tools like MangoHud that don't interfere with our applications' stability is paramount, so getting to the bottom of these Vulkan layer crashes is a big win for everyone.

Diving Deep into the Stack Trace: What's Going On?

Alright, let's put on our detective hats and peer into the cryptic world of the stack trace. This isn't just a bunch of random code; it's a map that shows us exactly what functions were being called when the program decided to segfault. When mpv crashes with MangoHud enabled, the stack trace provides vital clues, particularly when we see calls related to std::unordered_map and overlay_params within MangoHud's code. Specifically, we're seeing errors like std::__detail::_Hash_node<std::pair<...>>::_M_next and std::_Hashtable<...>::~_Hashtable, which are typically associated with the destruction of a hash map. This suggests that during the cleanup phase, or perhaps even before full initialization, something in MangoHud's internal data structures is getting corrupted or improperly handled. The presence of overlay_params::~overlay_params in the trace further reinforces the idea that an issue with how MangoHud's overlay parameters are being managed—either allocated, accessed, or deallocated—is at the heart of the problem. When an unordered_map gets corrupted, trying to destroy it can lead to a segfault as it attempts to free memory that's already freed, or that wasn't allocated correctly in the first place, or perhaps following a corrupted pointer to the next node in the hash table chain.

But wait, there's more! The stack trace also points to NVIDIA::get_instant_metrics_nvml and NVIDIA::get_samples_and_copy. Now, this is super interesting because the user primarily experiences the issue when the Vulkan device is pointing to the Intel GPU. Why would NVIDIA specific functions be in the stack trace during a crash on an Intel GPU? This could mean a few things, guys. It might indicate that MangoHud is attempting to query all available GPUs for metrics during its initialization, even if the primary rendering device is Intel. If the NVIDIA GPU or its drivers aren't fully ready or are being accessed incorrectly at that moment, it could trigger a problem. Alternatively, it could be a shared code path within MangoHud that's causing issues regardless of the active GPU, where the NVIDIA specific call just happens to be the last one on the stack before the underlying memory corruption manifests as a segfault. This interaction between MangoHud attempting to gather hardware metrics from various sources and mpv's Vulkan layer initialization is a prime candidate for a race condition or a state inconsistency.

The less common but equally troubling free(): corrupted unsorted chunks error, which leads to a SIGABRT, really drives home the idea of memory management gone awry. A SIGABRT usually signals that the program detected an internal inconsistency, often related to malloc/free operations. When the heap (where dynamic memory is allocated) becomes corrupted, subsequent memory operations can fail dramatically. This kind of error is notoriously tricky because the corruption might have happened much earlier than the actual crash, making it hard to pinpoint the original cause. It could be an mpv bug, a MangoHud bug, or an interaction between them, or even a driver bug exposing itself through these operations. The fact that specifying the NVIDIA GPU for vulkan-device makes the issue less likely, and subsequent launches on Intel become more stable, hints at an initialization timing issue. Perhaps the NVIDIA driver's longer initialization time accidentally sidesteps a race condition that quickly occurs with the Intel driver. Or, the very act of a successful launch somehow