[libcxx-commits] [PATCH] D94909: [libc++][VE] Support futex system call on VE

[Kazushi Marukawa via Phabricator via libcxx-commits]

kaz7 updated this revision to Diff 392799.
kaz7 added a comment.

Update implementation as suggested.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D94909/new/

https://reviews.llvm.org/D94909

Files:
  libcxx/src/atomic.cpp


Index: libcxx/src/atomic.cpp
===================================================================
--- libcxx/src/atomic.cpp
+++ libcxx/src/atomic.cpp
@@ -16,7 +16,9 @@
 #ifdef __linux__
 
 #include <unistd.h>
-#include <linux/futex.h>
+#if __has_include(<linux/futex.h>)
+#  include <linux/futex.h>
+#endif
 #include <sys/syscall.h>
 
 // libc++ uses SYS_futex as a universal syscall name. However, on 32 bit architectures
@@ -35,6 +37,27 @@
 
 #ifdef __linux__
 
+#  ifdef __ve__ && !defined(FUTEX_WAIT)
+// VE doesn't distribute linux/futex.h.  Hoever, SYS_futex is implemented
+// partially as described in "Difference points for system calls",
+// https://www.hpc.nec/documents/veos/en/Difference_Point_System_Calls.pdf.
+// It describes following futex operations are supported.
+//   FUTEX_WAIT
+//   FUTEX_WAKT
+//   FUTEX_PRIVATE_FLAG
+//
+// The values of those operations are available in glibc-ve at
+// https://github.com/veos-sxarr-NEC/glibc-ve/blob/master/sysdeps/unix/sysv/linux/ve/lowlevellock.h#L30-L43.
+//
+// So, we copy defined values here as a remedy until linux/futex.h is
+// distributed.
+#    define FUTEX_WAIT         0
+#    define FUTEX_WAKE         1
+#    define FUTEX_PRIVATE_FLAG 128
+#    define FUTEX_WAIT_PRIVATE (FUTEX_WAIT | FUTEX_PRIVATE_FLAG)
+#    define FUTEX_WAKE_PRIVATE (FUTEX_WAKE | FUTEX_PRIVATE_FLAG)
+#  endif // __ve__ && !defined(FUTEX_WAIT)
+
 static void __libcpp_platform_wait_on_address(__cxx_atomic_contention_t const volatile* __ptr,
                                               __cxx_contention_t __val)
 {


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