Crash guard: prevent loading of preset if it has caused crashes.

src/AlsaDriver.cpp

@@ -35,6 +35,7 @@
 #include "PiPedalException.hpp"
 #include "DummyAudioDriver.hpp"
 #include "SchedulerPriority.hpp"
+#include "CrashGuard.hpp"
 
 #include "CpuUse.hpp"
 
@@ -1595,6 +1596,8 @@ namespace pipedal
                     throw PiPedalStateException("Unable to start ALSA capture.");
                 }
 
+                CrashGuardLock crashGuardLock;
+                
                 cpuUse.SetStartTime(cpuUse.Now());
                 while (true)
                 {

src/CMakeLists.txt

@@ -206,6 +206,7 @@ else()
 endif()
 
 set (PIPEDAL_SOURCES
+    CrashGuard.cpp CrashGuard.hpp
     ModTemplateGenerator.cpp ModTemplateGenerator.hpp
     WebServerMod.cpp WebServerMod.hpp
     ModGui.cpp ModGui.hpp
@@ -767,6 +768,7 @@ add_executable(pipedal_latency_test
     DummyAudioDriver.cpp DummyAudioDriver.hpp
     JackConfiguration.hpp JackConfiguration.cpp
     JackServerSettings.hpp JackServerSettings.cpp
+    CrashGuard.cpp CrashGuard.hpp
     CpuUse.hpp
     CpuUse.cpp
     )

src/CrashGuard.cpp

@@ -0,0 +1,99 @@
+/*
+ *   Copyright (c) 2025 Robin E. R. Davies
+ *   All rights reserved.
+
+ *   Permission is hereby granted, free of charge, to any person obtaining a copy
+ *   of this software and associated documentation files (the "Software"), to deal
+ *   in the Software without restriction, including without limitation the rights
+ *   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ *   copies of the Software, and to permit persons to whom the Software is
+ *   furnished to do so, subject to the following conditions:
+
+ *   The above copyright notice and this permission notice shall be included in all
+ *   copies or substantial portions of the Software.
+
+ *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ *   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ *   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ *   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ *   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ *   SOFTWARE.
+ */
+
+#include "CrashGuard.hpp"
+#include "ofstream_synced.hpp"
+#include <fstream>
+#include <Lv2Log.hpp>
+
+using namespace pipedal;
+namespace fs = std::filesystem;
+
+int CrashGuard::crashCount = 0;
+std::mutex CrashGuard::mutex;
+std::filesystem::path CrashGuard::fileName;
+int64_t CrashGuard::depth = 0;
+
+void CrashGuard::SetCrashGuardFileName(const std::filesystem::path &path)
+{
+    CrashGuard::fileName = path;
+
+    {
+        std::ifstream f{path};
+        if (f.is_open())
+        {
+            f >> crashCount;
+        }
+        if (crashCount > 0) {
+            Lv2Log::info("CrashGuard: Detected previous crash, count = %d", (int)crashCount);
+        }
+    }
+}
+bool CrashGuard::HasCrashed()
+{
+    return crashCount > 4;
+}
+void CrashGuard::ClearCrashFlag()
+{
+    crashCount = 0;
+    try
+    {
+        if (fs::exists(fileName))
+        {
+            fs::remove(fileName);
+        }
+    }
+    catch (const std::exception &ignored)
+    {
+    }
+}
+
+void CrashGuard::EnterCrashGuardZone()
+{
+    std::lock_guard lock{mutex};
+
+    if (depth++ == 0)
+    {
+        if (!fileName.empty()) {
+            ofstream_synced f{fileName};
+            f << (crashCount + 1) << std::endl;
+        }
+    }
+}
+void CrashGuard::LeaveCrashGuardZone()
+{
+    std::lock_guard lock{mutex};
+    if (--depth == 0)
+    {
+        try
+        {
+            if (!fileName.empty() && fs::exists(fileName))
+            {
+                fs::remove(fileName);
+            }
+        }
+        catch (const std::exception &ignored)
+        {
+        }
+    }
+}

src/CrashGuard.hpp

@@ -0,0 +1,76 @@
+/*
+ *   Copyright (c) 2025 Robin E. R. Davies
+ *   All rights reserved.
+
+ *   Permission is hereby granted, free of charge, to any person obtaining a copy
+ *   of this software and associated documentation files (the "Software"), to deal
+ *   in the Software without restriction, including without limitation the rights
+ *   to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ *   copies of the Software, and to permit persons to whom the Software is
+ *   furnished to do so, subject to the following conditions:
+
+ *   The above copyright notice and this permission notice shall be included in all
+ *   copies or substantial portions of the Software.
+
+ *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ *   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ *   AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ *   LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ *   OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ *   SOFTWARE.
+ */
+
+#pragma once
+
+#include <mutex>
+#include <atomic>
+#include <filesystem>
+
+namespace pipedal
+{
+
+    /**
+     * @brief Crash protection.
+     *
+     * Detect the situation where PiPedal has crashed multiple times due to SIG_SEGVS caused by a plugin.
+     *
+     * The basic premise: mark segments of code as "crash protected". If Pipedal shuts down without exiting the
+     * crash guard zone for some fixed number of occasions (3?), then set a flag that will prevent
+     * loading of the default plugin when PiPedal next loads. Since PiPedal restarts indefinitely while
+     * running as a service, this allows users to recover after they have committed a plugin that crashes
+     * into their current preset.
+     *
+     */
+
+    class CrashGuard
+    {
+    public:
+        static void SetCrashGuardFileName(const std::filesystem::path &path);
+        static bool HasCrashed();
+        static void ClearCrashFlag();
+
+        static void EnterCrashGuardZone();
+        static void LeaveCrashGuardZone();
+
+    private:
+        static int crashCount;
+        static std::mutex mutex;
+        static std::filesystem::path fileName;
+        static int64_t depth;
+    };
+
+    class CrashGuardLock {
+    public:
+        CrashGuardLock() {
+            CrashGuard::EnterCrashGuardZone();
+        }
+        ~CrashGuardLock() {
+            CrashGuard::LeaveCrashGuardZone();
+        }
+        CrashGuardLock(const CrashGuardLock &) = delete;
+        CrashGuardLock &operator=(const CrashGuardLock &) = delete;
+        CrashGuardLock(CrashGuardLock &&) = delete;
+        CrashGuardLock &operator=(CrashGuardLock &&) = delete;
+    };
+};

src/DummyAudioDriver.cpp

@@ -38,6 +38,7 @@
 #include <stdexcept>
 #include "ss.hpp"
 #include "SchedulerPriority.hpp"
+#include "CrashGuard.hpp"
 
 #include "CpuUse.hpp"
 
@@ -287,6 +288,7 @@ namespace pipedal
 
                 bool ok = true;
 
+                CrashGuardLock crashGuardLock;
                 while (true)
                 {
 

src/Lv2Pedalboard.cpp

@@ -27,6 +27,7 @@
 #include "AudioHost.hpp"
 #include "Lv2EventBufferWriter.hpp"
 #include "Lv2Log.hpp"
+#include "CrashGuard.hpp"
 
 using namespace pipedal;
 
@@ -401,6 +402,8 @@ void Lv2Pedalboard::UpdateAudioPorts()
 
 void Lv2Pedalboard::Activate()
 {
+    CrashGuardLock crashGuardLock;
+    
     for (int i = 0; i < this->effects.size(); ++i)
     {
         this->realtimeEffects[i]->Activate();

src/PiPedalModel.cpp

@@ -45,6 +45,7 @@
 #include "AvahiService.hpp"
 #include "DummyAudioDriver.hpp"
 #include "AudioFiles.hpp"
+#include "CrashGuard.hpp"
 
 #ifndef NO_MLOCK
 #include <sys/mman.h>
@@ -271,20 +272,33 @@ void PiPedalModel::Load()
 
     this->pedalboard = storage.GetCurrentPreset(); // the current *saved* preset.
 
+
+
     // the current edited preset, saved only across orderly shutdowns.
-    CurrentPreset currentPreset;
-    try
-    {
-        if (storage.RestoreCurrentPreset(&currentPreset))
+
+    CrashGuard::SetCrashGuardFileName(storage.GetDataRoot() / "crash_guard.data");
+
+    if (CrashGuard::HasCrashed()) {
+        // ignore the current preset, and load a blank pedalboard in order to avoid a potential plugin crash.
+        this->pedalboard = Pedalboard::MakeDefault();
+    } else {
+        CurrentPreset currentPreset;
+        try
         {
-            this->pedalboard = currentPreset.preset_;
-            this->hasPresetChanged = currentPreset.modified_;
+            if (storage.RestoreCurrentPreset(&currentPreset))
+            {
+                this->pedalboard = currentPreset.preset_;
+                this->hasPresetChanged = currentPreset.modified_;
+            } 
+        }
+        catch (const std::exception &e)
+        {
+            Lv2Log::warning(SS("Failed to load current preset. " << e.what()));
         }
     }
-    catch (const std::exception &e)
-    {
-        Lv2Log::warning(SS("Failed to load current preset. " << e.what()));
-    }
+
+
+
     UpdateDefaults(&this->pedalboard);
 
     std::unique_ptr<AudioHost> p{AudioHost::CreateInstance(pluginHost.asIHost())};
@@ -2610,6 +2624,7 @@ void PiPedalModel::SetSelectedPedalboardPlugin(uint64_t clientId, uint64_t pedal
 
 bool PiPedalModel::LoadCurrentPedalboard()
 {
+    CrashGuardLock crashGuardLock;
     if (previousPedalboardLoaded && pedalboard.IsStructureIdentical(previousPedalboard))
     {
         // then we can send a snapshot update instead!