[sshfs] Use Timer and wrap posix signals

Author: Sploder12

include/multipass/platform_unix.h

@@ -22,12 +22,25 @@
 
 #include <signal.h>
 
-namespace multipass
+#include "singleton.h"
+
+#define MP_POSIX_SIGNAL multipass::platform::SignalWrapper::instance()
+
+namespace multipass::platform
 {
-namespace platform
+
+class SignalWrapper : public Singleton<SignalWrapper>
 {
+public:
+  SignalWrapper(const PrivatePass&) noexcept;
+
+  virtual int mask_signals(int how, const sigset_t* sigset, sigset_t* old_set = nullptr) const;
+  virtual int send(pthread_t target, int signal) const;
+  virtual int wait(const sigset_t& sigset, int& got) const;
+};
+
 sigset_t make_sigset(const std::vector<int>& sigs);
 sigset_t make_and_block_signals(const std::vector<int>& sigs);
-} // namespace platform
-}
+
+} // namespace multipass::platform
 #endif // MULTIPASS_PLATFORM_UNIX_H

src/platform/platform_unix.cpp

@@ -25,7 +25,7 @@
 #include <unistd.h>
 
 #include <libssh/sftp.h>
-#include <multipass/auto_join_thread.h>
+#include <multipass/timer.h>
 
 namespace mp = multipass;
 
@@ -158,6 +158,25 @@ int mp::platform::symlink_attr_from(const char* path, sftp_attributes_struct* at
     return 0;
 }
 
+mp::platform::SignalWrapper::SignalWrapper(const PrivatePass& pass) noexcept
+: Singleton(pass){}
+
+
+int mp::platform::SignalWrapper::mask_signals(int how, const sigset_t* sigset, sigset_t* old_set) const
+{
+    return pthread_sigmask(how, sigset, old_set);
+}
+
+int mp::platform::SignalWrapper::send(pthread_t target, int signal) const
+{
+    return pthread_kill(target, signal);
+}
+
+int mp::platform::SignalWrapper::wait(const sigset_t& sigset, int& got) const
+{
+    return sigwait(std::addressof(sigset), std::addressof(got));
+}
+
 sigset_t mp::platform::make_sigset(const std::vector<int>& sigs)
 {
     sigset_t sigset;
@@ -172,7 +191,7 @@ sigset_t mp::platform::make_sigset(const std::vector<int>& sigs)
 sigset_t mp::platform::make_and_block_signals(const std::vector<int>& sigs)
 {
     auto sigset{make_sigset(sigs)};
-    pthread_sigmask(SIG_BLOCK, &sigset, nullptr);
+    MP_POSIX_SIGNAL.mask_signals(SIG_BLOCK, &sigset, nullptr);
     return sigset;
 }
 
@@ -188,34 +207,25 @@ std::function<std::optional<int>(const std::function<bool()>&)> mp::platform::ma
 {
     return [sigset = make_and_block_signals({SIGQUIT, SIGTERM, SIGHUP, SIGUSR2}),
             period](const std::function<bool()>& condition) -> std::optional<int> {
-        std::mutex sig_mtx;
-        std::condition_variable sig_cv;
-        int sig = SIGUSR2;
-
-        // A signal generator that triggers after `timeout`
-        AutoJoinThread signaler([&sig_mtx, &sig_cv, &sig, &period, signalee = pthread_self()] {
-            std::unique_lock lock(sig_mtx);
-            while (!sig_cv.wait_for(lock, period, [&sig] { return sig != SIGUSR2; }))
-            {
-                pthread_kill(signalee, SIGUSR2);
-            }
-        });
+
+        // create a timer to periodically send SIGUSR2
+        utils::Timer signal_generator{period, [signalee = pthread_self()] {
+            MP_POSIX_SIGNAL.send(signalee, SIGUSR2);
+        }};
 
         // wait on signals and condition
         int latest_signal = SIGUSR2;
         while (latest_signal == SIGUSR2 && condition())
         {
+            signal_generator.start();
+
             // can't use sigtimedwait since macOS doesn't support it
-            sigwait(&sigset, &latest_signal);
+            MP_POSIX_SIGNAL.wait(sigset, latest_signal);
         }
 
-        { // set `sig` to something other than SIGUSR2 so `signaler` knows to exit
-            std::lock_guard lock(sig_mtx);
-            sig = latest_signal == SIGUSR2 ? 0 : latest_signal;
-        }
-        sig_cv.notify_all();
+        signal_generator.stop();
 
-        // if `sig` is 0 then we know we're exiting because condition() was false
-        return sig ? std::make_optional(sig) : std::nullopt;
+        // if `latest_signal` is SIGUSR2 then we know `condition()` is false
+        return latest_signal == SIGUSR2 ? std::nullopt : std::make_optional(latest_signal);
     };
 }