Aix: Prevent main thread from getting terminated with SIGPROF when

profiling is enabled

Bug: v8:12952

Change-Id: Ie3c3de71c5ca4be8256ac87e60b183bc45e47cf6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3696481Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Vasili Skurydzin <vasili.skurydzin@ibm.com>
Cr-Commit-Position: refs/heads/main@{#81075}

src/libsampler/sampler.cc

@@ -19,7 +19,11 @@
 #include <sys/syscall.h>
 #endif
 
-#if V8_OS_DARWIN
+#if V8_OS_AIX
+
+#include "src/base/platform/time.h"
+
+#elif V8_OS_DARWIN
 #include <mach/mach.h>
 // OpenBSD doesn't have <ucontext.h>. ucontext_t lives in <signal.h>
 // and is a typedef for struct sigcontext. There is no uc_mcontext.
@@ -343,8 +347,14 @@ class SignalHandler {
 
   static void Restore() {
     if (signal_handler_installed_) {
-      sigaction(SIGPROF, &old_signal_handler_, nullptr);
       signal_handler_installed_ = false;
+#if V8_OS_AIX
+      // On Aix & IBMi, SIGPROF can sometimes arrive after the default signal
+      // handler is restored, resulting in intermittent test failure when
+      // profiling is enabled (https://crbug.com/v8/12952)
+      base::OS::Sleep(base::TimeDelta::FromMicroseconds(10));
+#endif
+      sigaction(SIGPROF, &old_signal_handler_, nullptr);
     }
   }