Gracefully handle MADV_FREE available at compile time but not run time

base/allocator/partition_allocator/page_allocator.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/allocator/partition_allocator/page_allocator.h"
 
 #include <limits.h>
 
 #include "base/allocator/partition_allocator/address_space_randomization.h"
 #include "base/atomicops.h"
@@ skipping 198 matching lines @@
   return !mprotect(addr, len, PROT_READ | PROT_WRITE);
 #else
   return !!VirtualAlloc(addr, len, MEM_COMMIT, PAGE_READWRITE);
 #endif
 }
 
 void decommitSystemPages(void* addr, size_t len) {
   DCHECK(!(len & kSystemPageOffsetMask));
 #if defined(OS_POSIX)
   int ret = madvise(addr, len, MADV_FREE);
+  if (ret != 0 && errno == EINVAL) {
+    // MADV_FREE only works on Linux 4.5+ . If request failed,
+    // retry with older MADV_DONTNEED . Note that MADV_FREE
+    // being defined at compile time doesn't imply runtime support.
+    ret = madvise(addr, len, MADV_DONTNEED);
+  }
   CHECK(!ret);
 #else
   setSystemPagesInaccessible(addr, len);
 #endif
 }
 
 void recommitSystemPages(void* addr, size_t len) {
   DCHECK(!(len & kSystemPageOffsetMask));
 #if defined(OS_POSIX)
   (void)addr;
@@ skipping 34 matching lines @@
     CHECK(ret);
   }
 #endif
 }
 
 uint32_t getAllocPageErrorCode() {
   return base::subtle::Acquire_Load(&s_allocPageErrorCode);
 }
 
 }  // namespace base