Revert "[libc] skip test and return ENOSYS when processm_release unavailable (llvm#117951)"

This reverts commit 819b155.

Author: SchrodingerZhu

libc/src/sys/mman/linux/process_mrelease.cpp

@@ -19,7 +19,6 @@
 namespace LIBC_NAMESPACE_DECL {
 
 LLVM_LIBC_FUNCTION(int, process_mrelease, (int pidfd, unsigned int flags)) {
-#ifdef SYS_process_mrelease
   long ret =
       LIBC_NAMESPACE::syscall_impl<int>(SYS_process_mrelease, pidfd, flags);
 
@@ -29,13 +28,6 @@ LLVM_LIBC_FUNCTION(int, process_mrelease, (int pidfd, unsigned int flags)) {
   }
 
   return 0;
-#else
-  // The system call is not available.
-  (void)pidfd;
-  (void)flags;
-  libc_errno = ENOSYS;
-  return -1;
-#endif
 }
 
 } // namespace LIBC_NAMESPACE_DECL

libc/test/src/sys/mman/linux/CMakeLists.txt

@@ -197,7 +197,6 @@ add_libc_unittest(
     libc.src.signal.kill
     libc.include.signal
     libc.src.stdlib.exit
-    libc.src.signal.raise
     libc.src.__support.OSUtil.osutil
     libc.src.__support.threads.sleep
     libc.test.UnitTest.ErrnoSetterMatcher

libc/test/src/sys/mman/linux/process_mrelease_test.cpp

@@ -7,9 +7,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/threads/sleep.h"
 #include "src/errno/libc_errno.h"
 #include "src/signal/kill.h"
-#include "src/signal/raise.h"
 #include "src/stdlib/exit.h"
 #include "src/sys/mman/process_mrelease.h"
 #include "src/unistd/close.h"
@@ -18,7 +18,7 @@
 #include "test/UnitTest/LibcTest.h"
 
 #include <sys/syscall.h>
-#if defined(SYS_process_mrelease) && defined(SYS_pidfd_open)
+
 using namespace LIBC_NAMESPACE::testing::ErrnoSetterMatcher;
 
 int pidfd_open(pid_t pid, unsigned int flags) {
@@ -30,11 +30,13 @@ TEST(LlvmLibcProcessMReleaseTest, NoError) {
   EXPECT_GE(child_pid, 0);
 
   if (child_pid == 0) {
-    // pause the child process
-    LIBC_NAMESPACE::raise(SIGSTOP);
+    // Child process: wait a bit then exit gracefully.
+    LIBC_NAMESPACE::sleep_briefly();
+    LIBC_NAMESPACE::exit(0);
   } else {
     // Parent process: wait a bit and then kill the child.
     // Give child process some time to start.
+    LIBC_NAMESPACE::sleep_briefly();
     int pidfd = pidfd_open(child_pid, 0);
     EXPECT_GE(pidfd, 0);
 
@@ -52,9 +54,12 @@ TEST(LlvmLibcProcessMReleaseTest, ErrorNotKilled) {
   EXPECT_GE(child_pid, 0);
 
   if (child_pid == 0) {
-    // pause the child process
-    LIBC_NAMESPACE::raise(SIGSTOP);
+    // Child process: wait a bit then exit gracefully.
+    LIBC_NAMESPACE::sleep_briefly();
+    LIBC_NAMESPACE::exit(0);
   } else {
+    // Give child process some time to start.
+    LIBC_NAMESPACE::sleep_briefly();
     int pidfd = pidfd_open(child_pid, 0);
     EXPECT_GE(pidfd, 0);
 
@@ -67,4 +72,3 @@ TEST(LlvmLibcProcessMReleaseTest, ErrorNotKilled) {
 TEST(LlvmLibcProcessMReleaseTest, ErrorNonExistingPidfd) {
   EXPECT_THAT(LIBC_NAMESPACE::process_mrelease(-1, 0), Fails(EBADF));
 }
-#endif