From 3cb8ae9a9c162bbd45b071bd406ff39d88e3e111 Mon Sep 17 00:00:00 2001
From: Stefanos Kornilios Misis Poiitidis <skmp@nilware.io>
Date: Sat, 30 Apr 2022 16:00:00 +0300
Subject: [PATCH] ScopedSignalMask: Add shared mutex support, move constructors

---
 .../FEXHeaderUtils/ScopedSignalMask.h         | 129 ++++++++++++++++--
 1 file changed, 121 insertions(+), 8 deletions(-)

diff --git a/FEXHeaderUtils/FEXHeaderUtils/ScopedSignalMask.h b/FEXHeaderUtils/FEXHeaderUtils/ScopedSignalMask.h
index 071ef010d..b44cc427b 100644
--- a/FEXHeaderUtils/FEXHeaderUtils/ScopedSignalMask.h
+++ b/FEXHeaderUtils/FEXHeaderUtils/ScopedSignalMask.h
@@ -5,6 +5,7 @@
 
 #include <cstdint>
 #include <mutex>
+#include <shared_mutex>
 #include <signal.h>
 #include <sys/syscall.h>
 #include <unistd.h>
@@ -20,27 +21,139 @@ namespace FHU {
    * Destructor Order:
    * 1) Unlock Mutex
    * 2) Unmask signals
+   *
+   * Masking signals around mutex locks is needed for signal-reentrant safety
    */
   class ScopedSignalMaskWithMutex final {
     public:
+
       ScopedSignalMaskWithMutex(std::mutex &_Mutex, uint64_t Mask = ~0ULL)
-        : Mutex {_Mutex} {
+        : Mutex {&_Mutex} {
         // Mask all signals, storing the original incoming mask
         ::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &Mask, &OriginalMask, sizeof(OriginalMask));
 
         // Lock the mutex
-        Mutex.lock();
+        Mutex->lock();
+      }
+
+      // No copy or assignment possible
+      ScopedSignalMaskWithMutex(const ScopedSignalMaskWithMutex&) = delete;
+      ScopedSignalMaskWithMutex& operator=(ScopedSignalMaskWithMutex&) = delete;
+
+      // Only move
+      ScopedSignalMaskWithMutex(ScopedSignalMaskWithMutex &&rhs)
+       : OriginalMask {rhs.OriginalMask}, Mutex {rhs.Mutex} {
+        rhs.Mutex = nullptr;
       }
 
       ~ScopedSignalMaskWithMutex() {
-        // Unlock the mutex
-        Mutex.unlock();
+        if (Mutex != nullptr) {
+          // Unlock the mutex
+          Mutex->unlock();
 
-        // Unmask back to the original signal mask
-        ::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &OriginalMask, nullptr, sizeof(OriginalMask));
+          // Unmask back to the original signal mask
+          ::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &OriginalMask, nullptr, sizeof(OriginalMask));
+        }
       }
     private:
       uint64_t OriginalMask{};
-      std::mutex &Mutex;
+      std::mutex *Mutex;
   };
-}
+
+  /**
+   * @brief A class that masks signals and shared locks a shared mutex until it goes out of scope
+   *
+   * Constructor order:
+   * 1) Mask signals
+   * 2) Lock Mutex
+   *
+   * Destructor Order:
+   * 1) Unlock Mutex
+   * 2) Unmask signals
+   *
+   * Masking signals around mutex locks is needed for signal-rentrant safety
+   */
+  class ScopedSignalMaskWithSharedLock final {
+    public:
+      ScopedSignalMaskWithSharedLock(std::shared_mutex &_Mutex, uint64_t Mask = ~0ULL)
+        : Mutex {&_Mutex} {
+        // Mask all signals, storing the original incoming mask
+        ::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &Mask, &OriginalMask, sizeof(OriginalMask));
+
+        // Lock the mutex
+        Mutex->lock_shared();
+      }
+
+      // No copy or assignment possible
+      ScopedSignalMaskWithSharedLock(const ScopedSignalMaskWithSharedLock&) = delete;
+      ScopedSignalMaskWithSharedLock& operator=(ScopedSignalMaskWithSharedLock&) = delete;
+
+      // Only move
+      ScopedSignalMaskWithSharedLock(ScopedSignalMaskWithSharedLock &&rhs)
+       : OriginalMask {rhs.OriginalMask}, Mutex {rhs.Mutex} {
+        rhs.Mutex = nullptr;
+      }
+
+      ~ScopedSignalMaskWithSharedLock() {
+        if (Mutex) {
+          // Unlock the mutex
+          Mutex->unlock_shared();
+          
+          // Unmask back to the original signal mask
+          ::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &OriginalMask, nullptr, sizeof(OriginalMask));
+        }
+      }
+    private:
+      uint64_t OriginalMask{};
+      std::shared_mutex *Mutex;
+  };
+
+
+  /**
+   * @brief A class that masks signals and unique locks a shared mutex until it goes out of scope
+   *
+   * Constructor order:
+   * 1) Mask signals
+   * 2) Lock Mutex
+   *
+   * Destructor Order:
+   * 1) Unlock Mutex
+   * 2) Unmask signals
+   *
+   * Masking signals around mutex locks is needed for signal-rentrant safety
+   */
+  class ScopedSignalMaskWithUniqueLock final {
+    public:
+      ScopedSignalMaskWithUniqueLock(std::shared_mutex &_Mutex, uint64_t Mask = ~0ULL)
+        : Mutex {&_Mutex} {
+        // Mask all signals, storing the original incoming mask
+        ::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &Mask, &OriginalMask, sizeof(OriginalMask));
+
+        // Lock the mutex
+        Mutex->lock();
+      }
+
+      // No copy or assignment possible
+      ScopedSignalMaskWithUniqueLock(const ScopedSignalMaskWithSharedLock&) = delete;
+      ScopedSignalMaskWithUniqueLock& operator=(ScopedSignalMaskWithSharedLock&) = delete;
+
+      ScopedSignalMaskWithUniqueLock(ScopedSignalMaskWithUniqueLock &&rhs)
+        : OriginalMask {rhs.OriginalMask}, Mutex {rhs.Mutex} {
+        rhs.Mutex = nullptr;
+      }
+
+      ~ScopedSignalMaskWithUniqueLock() {
+        if (Mutex != nullptr)
+        {
+          // Unlock the mutex
+          Mutex->unlock();
+          
+          // Unmask back to the original signal mask
+          ::syscall(SYS_rt_sigprocmask, SIG_SETMASK, &OriginalMask, nullptr, sizeof(OriginalMask));
+        }
+      }
+    private:
+      uint64_t OriginalMask{};
+      std::shared_mutex *Mutex;
+  };
+}
\ No newline at end of file