Fix EINTR handling

src/connection.cpp

@@ -28,7 +28,10 @@ Connection::~Connection() {
   if (auto server_ptr = server_.lock()) {
     server_ptr->active_connections_.fetch_sub(1, std::memory_order_relaxed);
   }
-  int e = close(fd_);
+  int e;
+  do {
+    e = close(fd_);
+  } while (e == -1 && errno == EINTR);
   if (e == -1) {
     perror("close");
     std::abort();

src/main.cpp

@@ -48,7 +48,10 @@ std::vector<int> create_listen_sockets(const weaseldb::Config &config) {
     addr.sun_family = AF_UNIX;
 
     if (config.server.unix_socket_path.length() >= sizeof(addr.sun_path)) {
-      close(sfd);
+      int e;
+      do {
+        e = close(sfd);
+      } while (e == -1 && errno == EINTR);
       std::fprintf(stderr, "Unix socket path too long\n");
       std::abort();
     }
@@ -58,13 +61,19 @@ std::vector<int> create_listen_sockets(const weaseldb::Config &config) {
 
     if (bind(sfd, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
       perror("bind");
-      close(sfd);
+      int e;
+      do {
+        e = close(sfd);
+      } while (e == -1 && errno == EINTR);
       std::abort();
     }
 
     if (listen(sfd, SOMAXCONN) == -1) {
       perror("listen");
-      close(sfd);
+      int e;
+      do {
+        e = close(sfd);
+      } while (e == -1 && errno == EINTR);
       std::abort();
     }
 
@@ -103,7 +112,10 @@ std::vector<int> create_listen_sockets(const weaseldb::Config &config) {
     int val = 1;
     if (setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val)) == -1) {
       perror("setsockopt SO_REUSEADDR");
-      close(sfd);
+      int e;
+      do {
+        e = close(sfd);
+      } while (e == -1 && errno == EINTR);
       continue;
     }
 
@@ -111,7 +123,10 @@ std::vector<int> create_listen_sockets(const weaseldb::Config &config) {
     if (rp->ai_family == AF_INET || rp->ai_family == AF_INET6) {
       if (setsockopt(sfd, IPPROTO_TCP, TCP_NODELAY, &val, sizeof(val)) == -1) {
         perror("setsockopt TCP_NODELAY");
-        close(sfd);
+        int e;
+        do {
+          e = close(sfd);
+        } while (e == -1 && errno == EINTR);
         continue;
       }
     }
@@ -120,7 +135,10 @@ std::vector<int> create_listen_sockets(const weaseldb::Config &config) {
       break; /* Success */
     }
 
-    close(sfd);
+    int e;
+    do {
+      e = close(sfd);
+    } while (e == -1 && errno == EINTR);
     sfd = -1;
   }
 
@@ -133,7 +151,10 @@ std::vector<int> create_listen_sockets(const weaseldb::Config &config) {
 
   if (listen(sfd, SOMAXCONN) == -1) {
     perror("listen");
-    close(sfd);
+    int e;
+    do {
+      e = close(sfd);
+    } while (e == -1 && errno == EINTR);
     std::abort();
   }
 

src/server.cpp

@@ -59,18 +59,27 @@ Server::Server(const weaseldb::Config &config, ConnectionHandler &handler,
 
 Server::~Server() {
   if (shutdown_pipe_[0] != -1) {
-    close(shutdown_pipe_[0]);
+    int e;
+    do {
+      e = close(shutdown_pipe_[0]);
+    } while (e == -1 && errno == EINTR);
     shutdown_pipe_[0] = -1;
   }
   if (shutdown_pipe_[1] != -1) {
-    close(shutdown_pipe_[1]);
+    int e;
+    do {
+      e = close(shutdown_pipe_[1]);
+    } while (e == -1 && errno == EINTR);
     shutdown_pipe_[1] = -1;
   }
 
   // Close all epoll instances
   for (int epollfd : epoll_fds_) {
     if (epollfd != -1) {
-      close(epollfd);
+      int e;
+      do {
+        e = close(epollfd);
+      } while (e == -1 && errno == EINTR);
     }
   }
   epoll_fds_.clear();
@@ -78,7 +87,10 @@ Server::~Server() {
   // Close all listen sockets (Server always owns them)
   for (int fd : listen_fds_) {
     if (fd != -1) {
-      close(fd);
+      int e;
+      do {
+        e = close(fd);
+      } while (e == -1 && errno == EINTR);
     }
   }
 
@@ -214,8 +226,13 @@ int Server::createLocalConnection() {
   if (epoll_ctl(epollfd, EPOLL_CTL_ADD, server_fd, &event) == -1) {
     perror("epoll_ctl ADD local connection");
     connection_registry_.remove(server_fd);
-    close(server_fd);
+    int e;
-    close(client_fd);
+    do {
+      e = close(server_fd);
+    } while (e == -1 && errno == EINTR);
+    do {
+      e = close(client_fd);
+    } while (e == -1 && errno == EINTR);
     return -1;
   }
 
@@ -367,7 +384,10 @@ void Server::start_io_threads(std::vector<std::thread> &threads) {
             if (config_.server.max_connections > 0 &&
                 active_connections_.load(std::memory_order_relaxed) >=
                     config_.server.max_connections) {
-              close(fd);
+              int e;
+              do {
+                e = close(fd);
+              } while (e == -1 && errno == EINTR);
               continue;
             }
 

style.md

@@ -329,6 +329,41 @@ static_assert(std::is_trivially_destructible_v<T>, "Arena requires trivially des
 // assert(file_exists(path));  // File might legitimately not exist - use return code instead
 ```
 
+### System Call Error Handling
+
+When a system call is interrupted by a signal (`EINTR`), it is usually necessary to retry the call. This is especially true for "slow" system calls that can block for a long time, such as `read`, `write`, `accept`, `connect`, `close`, `sem_wait`, and `epoll_wait`.
+
+**Rule:** Always wrap potentially interruptible system calls in a `do-while` loop that checks for `EINTR`.
+
+**Example:**
+
+```cpp
+int fd;
+do {
+  fd = accept(listen_fd, nullptr, nullptr);
+} while (fd == -1 && errno == EINTR);
+
+if (fd == -1) {
+  // Handle other errors
+  perror("accept");
+  abort();
+}
+```
+
+
+**Non-interruptible calls:**
+
+Most system calls are not interruptible in practice. For these, it is not necessary to add a retry loop. This includes:
+
+*   `fcntl` (with `F_GETFL`, `F_SETFL`, `F_GETFD`, `F_SETFD` - note: `F_SETLKW` and `F_OFD_SETLKW` CAN return EINTR)
+*   `epoll_ctl`
+*   `socketpair`
+*   `pipe`
+*   `setsockopt`
+*   `epoll_create1`
+
+When in doubt, consult the `man` page for the specific system call to see if it can return `EINTR`.
+
 ---
 
 ## Documentation

tests/test_server_connection_return.cpp

@@ -69,12 +69,18 @@ TEST_CASE(
 
   // Write some test data
   const char *test_message = "Hello, World!";
-  ssize_t bytes_written = write(client_fd, test_message, strlen(test_message));
+  ssize_t bytes_written;
+  do {
+    bytes_written = write(client_fd, test_message, strlen(test_message));
+  } while (bytes_written == -1 && errno == EINTR);
   REQUIRE(bytes_written == strlen(test_message));
 
   // Read the echoed response
   char buffer[1024] = {0};
-  ssize_t bytes_read = read(client_fd, buffer, sizeof(buffer) - 1);
+  ssize_t bytes_read;
+  do {
+    bytes_read = read(client_fd, buffer, sizeof(buffer) - 1);
+  } while (bytes_read == -1 && errno == EINTR);
   if (bytes_read == -1) {
     perror("read failed");
   }
@@ -84,7 +90,10 @@ TEST_CASE(
   CHECK(std::string(buffer, bytes_read) == std::string(test_message));
 
   // Cleanup
-  close(client_fd);
+  int e;
+  do {
+    e = close(client_fd);
+  } while (e == -1 && errno == EINTR);
   server->shutdown();
   server_thread.join();
   {

tools/load_tester.cpp

@@ -85,11 +85,19 @@ int getConnectFd(const char *node, const char *service) {
       continue;
     }
 
-    if (connect(sfd, rp->ai_addr, rp->ai_addrlen) == 0) {
+    int conn_result;
+    do {
+      conn_result = connect(sfd, rp->ai_addr, rp->ai_addrlen);
+    } while (conn_result == -1 && errno == EINTR);
+
+    if (conn_result == 0) {
       break; /* Success */
     }
 
-    close(sfd);
+    int e;
+    do {
+      e = close(sfd);
+    } while (e == -1 && errno == EINTR);
   }
 
   freeaddrinfo(result); /* No longer needed */
@@ -113,7 +121,10 @@ int getConnectFdUnix(const char *socket_name) {
   memset(&addr, 0, sizeof(addr));
   addr.sun_family = AF_UNIX;
   strncpy(addr.sun_path, socket_name, sizeof(addr.sun_path) - 1);
-  int e = connect(sfd, (struct sockaddr *)&addr, sizeof(addr));
+  int e;
+  do {
+    e = connect(sfd, (struct sockaddr *)&addr, sizeof(addr));
+  } while (e == -1 && errno == EINTR);
   if (e == -1) {
     perror("connect");
     abort();
@@ -241,7 +252,10 @@ struct Connection {
   bool error = false;
 
   ~Connection() {
-    int e = close(fd);
+    int e;
+    do {
+      e = close(fd);
+    } while (e == -1 && errno == EINTR);
     if (e == -1) {
       perror("close");
       abort();
@@ -711,7 +725,9 @@ int main(int argc, char *argv[]) {
       while (!g_shutdown.load(std::memory_order_relaxed)) {
         int e;
         {
-          e = sem_wait(&connectionLimit);
+          do {
+            e = sem_wait(&connectionLimit);
+          } while (e == -1 && errno == EINTR);
           if (e == -1) {
             perror("sem_wait");
             abort();
@@ -814,6 +830,9 @@ int main(int argc, char *argv[]) {
 
   // Clean up epoll file descriptors
   for (int epollfd : g_epoll_fds) {
-    close(epollfd);
+    int e;
+    do {
+      e = close(epollfd);
+    } while (e == -1 && errno == EINTR);
   }
 }