Fix EINTR handling

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