daemon: Phase 0 platform seams (ADR 0020) — eventfd/SO_PEERCRED/instance-lock/XDG behind platform/, zero behaviour change

Introduces the four rpc-layer seams docs/08-porting.md calls for this lane: platform::Wakeup (eventfd), platform::peer_of (SO_PEERCRED/struct ucred, same-UID check preserved unchanged), platform::acquire_instance_lock (abstract-namespace socket), platform::runtime_base_dir/data_base_dir (XDG lookups). Today's Linux code moves unchanged into daemon/src/rpc/platform/linux/; the seam headers carry no OS types and no #ifdef. No fifth interface for timerfd: EventLoop gains a portable add_timer() that folds the next deadline into poll()'s own timeout, replacing both timerfd instances in main.cpp — the loop already computes a deadline, so this needs no per-OS backend at all. Full suite 59/59 green; no #ifdef outside platform/linux/, no behaviour change. Co-Authored-By: Claude Sonnet 5 <[email protected]>
2026-09-15 17:54:32 +04:00
parent 4e87730ce9
commit 6d7c4f7bc4
17 changed files with 321 additions and 143 deletions
@@ -0,0 +1,36 @@
+#pragma once
+
+// The event-loop wakeup primitive (docs/adr/0020, docs/08-porting.md). EventLoop uses this
+// to interrupt a blocked poll() from another thread or a signal handler — the eventfd
+// mechanics themselves are Linux-only; every other OS backend just needs something
+// poll()-able that signal()/drain() can drive the same way (docs/08 §"The seams": a
+// self-pipe on macOS, an event object on Windows).
+//
+// One implementation file per OS under platform/<os>/wakeup.cpp; this header carries no
+// OS types and no #ifdef (ADR 0020 decision 1).
+
+namespace velox::daemon::rpc::platform {
+
+class Wakeup {
+public:
+    Wakeup();
+    ~Wakeup();
+
+    Wakeup(const Wakeup&) = delete;
+    Wakeup& operator=(const Wakeup&) = delete;
+
+    // The fd to register with poll(2) for readability.
+    int pollfd() const noexcept { return fd_; }
+
+    // Make pollfd() readable. Async-signal-safe and thread-safe.
+    void signal() noexcept;
+
+    // Drain whatever signal() queued so pollfd() stops being readable. Call this from the
+    // loop thread once pollfd() fires.
+    void drain() noexcept;
+
+private:
+    int fd_ = -1;
+};
+
+}  // namespace velox::daemon::rpc::platform