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src/hotspot/os/aix/safepointMechanism_aix.cpp

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rev 50788 : 8205609: [PPC64] Fix PPC64 part of 8010319 and TLH without UseSIGTRAP on AIX
Reviewed-by: dholmes

@@ -36,11 +36,11 @@
     return;
   }
 
   // Allocate one protected page
   char* map_address = (char*)MAP_FAILED;
-  const size_t page_size = os::vm_page_size();
+  const size_t map_size = ThreadLocalHandshakes ? 2 * os::vm_page_size() : os::vm_page_size();
   const int prot  = PROT_READ;
   const int flags = MAP_PRIVATE | MAP_ANONYMOUS;
 
   // Use optimized addresses for the polling page,
   // e.g. map it to a special 32-bit address.

@@ -66,11 +66,11 @@
     for (int i = 0; i < address_wishes_length; i++) {
       // Try to map with current address wish.
       // AIX: AIX needs MAP_FIXED if we provide an address and mmap will
       // fail if the address is already mapped.
       map_address = (char*) ::mmap(address_wishes[i],
-                                   page_size, prot,
+                                   map_size, prot,
                                    flags | MAP_FIXED,
                                    -1, 0);
       log_debug(os)("SafePoint Polling Page address: %p (wish) => %p",
                     address_wishes[i], map_address);
 

@@ -79,26 +79,29 @@
         break;
       }
 
       if (map_address != (char*)MAP_FAILED) {
         // Map succeeded, but polling_page is not at wished address, unmap and continue.
-        ::munmap(map_address, page_size);
+        ::munmap(map_address, map_size);
         map_address = (char*)MAP_FAILED;
       }
       // Map failed, continue loop.
     }
   }
   if (map_address == (char*)MAP_FAILED) {
-    map_address = (char*) ::mmap(NULL, page_size, prot, flags, -1, 0);
+    map_address = (char*) ::mmap(NULL, map_size, prot, flags, -1, 0);
   }
-  guarantee(map_address != (char*)MAP_FAILED, "SafepointMechanism::pd_initialize: failed to allocate polling page");
+  guarantee(map_address != (char*)MAP_FAILED && map_address != NULL,
+            "SafepointMechanism::pd_initialize: failed to allocate polling page");
   log_info(os)("SafePoint Polling address: " INTPTR_FORMAT, p2i(map_address));
   os::set_polling_page((address)(map_address));
 
   // Use same page for ThreadLocalHandshakes without SIGTRAP
   if (ThreadLocalHandshakes) {
     set_uses_thread_local_poll();
-    intptr_t bad_page_val = reinterpret_cast<intptr_t>(map_address);
-    _poll_armed_value    = reinterpret_cast<void*>(bad_page_val | poll_bit());
-    _poll_disarmed_value = NULL; // Readable on AIX
+    os::make_polling_page_unreadable();
+    intptr_t bad_page_val  = reinterpret_cast<intptr_t>(map_address),
+             good_page_val = bad_page_val + os::vm_page_size();
+    _poll_armed_value    = reinterpret_cast<void*>(bad_page_val  + poll_bit());
+    _poll_disarmed_value = reinterpret_cast<void*>(good_page_val);
   }
 }
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