ext/pcntl: adding pcntl_getcpu.

using sched_getcpu under the hood (Linux and FreeBSD).
Returns the current cpu id for the current process.
For Linux, we need to see beyond the sole presence of the symbol
to consider it.
Mostly useful, for now, in the cpu affinity context since
the os can migrate processes as it sees fits otherwise.

Clos GH-13908

Author: devnexen

NEWS

@@ -127,6 +127,7 @@ PHP                                                                        NEWS
   . Added pcntl_getaffinity/pcntl_setaffinity. (David Carlier)
   . Updated pcntl_get_signal_handler signal id upper limit to be
     more in line with platforms limits. (David Carlier)
+  . Added pcntl_getcpu for Linux/FreeBSD. (David Carlier)
 
 - PCRE:
   . Upgrade bundled pcre2lib to version 10.43. (nielsdos)

UPGRADING

@@ -447,6 +447,7 @@ PHP 8.4 UPGRADE NOTES
     to share resources with other processes within this context.
   . Added pcntl_getaffinity to get the cpu(s) bound to a process and
     pcntl_setaffinity to bind 1 or more cpus to a process.
+  . Added pcntl_getcpu to get the cpu id from where the current process runs.
 
 - Sodium:
   . Added the sodium_crypto_aead_aegis128l_*() and sodium_crypto_aead_aegis256l_*()

ext/pcntl/config.m4

@@ -9,6 +9,25 @@ if test "$PHP_PCNTL" != "no"; then
   AC_CHECK_FUNCS([sigaction], [], [AC_MSG_ERROR([pcntl: sigaction() not supported by this platform])])
   AC_CHECK_FUNCS([getpriority setpriority wait3 wait4 sigwaitinfo sigtimedwait unshare rfork forkx pidfd_open sched_setaffinity])
 
+  dnl if unsupported, -1 means automatically ENOSYS in this context
+  AC_MSG_CHECKING([if sched_getcpu is supported])
+  AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <sched.h>
+int main(void) {
+  if (sched_getcpu() == -1) {
+      return 1;
+  }
+  return 0;
+}
+  ]])],[
+    AC_MSG_RESULT(yes)
+    AC_DEFINE([HAVE_SCHED_GETCPU],1,[Whether sched_getcpu is properly supported])
+  ],[
+    AC_MSG_RESULT(no)
+  ],[
+    AC_MSG_RESULT([no, cross-compiling])
+  ])
+
   AC_CHECK_TYPE([siginfo_t],[PCNTL_CFLAGS="-DHAVE_STRUCT_SIGINFO_T"],,[#include <signal.h>])
 
   PHP_NEW_EXTENSION(pcntl, pcntl.c php_signal.c, $ext_shared, cli, $PCNTL_CFLAGS -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1)

ext/pcntl/pcntl.c

@@ -42,7 +42,7 @@
 #endif
 
 #include <errno.h>
-#if defined(HAVE_UNSHARE) || defined(HAVE_SCHED_SETAFFINITY)
+#if defined(HAVE_UNSHARE) || defined(HAVE_SCHED_SETAFFINITY) || defined(HAVE_SCHED_GETCPU)
 #include <sched.h>
 #if defined(__FreeBSD__)
 #include <sys/types.h>
@@ -1613,6 +1613,15 @@ PHP_FUNCTION(pcntl_setcpuaffinity)
 }
 #endif
 
+#if defined(HAVE_SCHED_GETCPU)
+PHP_FUNCTION(pcntl_getcpu)
+{
+	ZEND_PARSE_PARAMETERS_NONE();
+
+	RETURN_LONG(sched_getcpu());
+}
+#endif
+
 static void pcntl_interrupt_function(zend_execute_data *execute_data)
 {
 	pcntl_signal_dispatch();

ext/pcntl/pcntl.stub.php

@@ -999,3 +999,7 @@ function pcntl_setns(?int $process_id = null, int $nstype = CLONE_NEWNET): bool
 function pcntl_getcpuaffinity(?int $process_id = null): array|false {}
 function pcntl_setcpuaffinity(?int $process_id = null, array $cpu_ids = []): bool {}
 #endif
+
+#ifdef HAVE_SCHED_GETCPU
+function pcntl_getcpu(): int {}
+#endif

ext/pcntl/pcntl_arginfo.h

@@ -0,0 +1,23 @@
+--TEST--
+pcntl_getcpu()
+--EXTENSIONS--
+pcntl
+--SKIPIF--
+<?php
+if (!function_exists("pcntl_getcpu")) die("skip pcntl_getcpu() is not available");
+if (!function_exists("pcntl_setcpuaffinity")) die("skip pcntl_setcpuaffinity() is not available");
+if (getenv('TRAVIS')) die('skip Currently fails on Travis');
+?>
+--FILE--
+<?php
+$pid = pcntl_fork();
+if ($pid == -1) {
+	die("fork failed");
+} else if ($pid == 0) {
+	var_dump(pcntl_setcpuaffinity(null, [1]));
+	var_dump(pcntl_getcpu());
+}
+?>
+--EXPECTF--
+bool(true)
+int(1)