Remove PO_DEBUG from build.yaml and move it to ev_epoll_linux.c

Makefile

@@ -111,7 +111,7 @@ CXX_dbg = $(DEFAULT_CXX)
 LD_dbg = $(DEFAULT_CC)
 LDXX_dbg = $(DEFAULT_CXX)
 CPPFLAGS_dbg = -O0
-DEFINES_dbg = _DEBUG DEBUG PO_DEBUG
+DEFINES_dbg = _DEBUG DEBUG
 
 VALID_CONFIG_easan = 1
 REQUIRE_CUSTOM_LIBRARIES_easan = 1

build.yaml

@@ -3699,7 +3699,7 @@ configs:
     DEFINES: NDEBUG
   dbg:
     CPPFLAGS: -O0
-    DEFINES: _DEBUG DEBUG PO_DEBUG
+    DEFINES: _DEBUG DEBUG
   easan:
     CC: clang
     CPPFLAGS: -O0 -fsanitize-coverage=edge -fsanitize=address -fno-omit-frame-pointer

src/core/lib/iomgr/ev_epoll_linux.c

@@ -69,6 +69,9 @@ static int grpc_polling_trace = 0; /* Disabled by default */
     gpr_log(GPR_INFO, (fmt), __VA_ARGS__); \
   }
 
+/* Uncomment the following enable extra checks on poll_object operations */
+/* #define PO_DEBUG */
+
 static int grpc_wakeup_signal = -1;
 static bool is_grpc_wakeup_signal_initialized = false;