From: Debian Haskell Group <pkg-haskell-maintainers@lists.alioth.debian.org>
Date: Sat, 17 Dec 2016 02:44:45 +0000 (+0000)
Subject: osdecommitmemory-compat
X-Git-Tag: archive/raspbian/8.0.2-9+rpi1~1^2~3
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=ea27ca07e55e4ef76ab7743e3627956298f7bbe5;p=ghc.git

osdecommitmemory-compat


Gbp-Pq: Name osdecommitmemory-compat.patch
---

diff --git a/rts/posix/OSMem.c b/rts/posix/OSMem.c
index 2a3c294f..0a9690c0 100644
--- a/rts/posix/OSMem.c
+++ b/rts/posix/OSMem.c
@@ -506,11 +506,24 @@ void osDecommitMemory(void *at, W_ size)
 
 #ifdef MADV_FREE
     // Try MADV_FREE first, FreeBSD has both and MADV_DONTNEED
-    // just swaps memory out
+    // just swaps memory out. Linux >= 4.5 has both DONTNEED and FREE; either
+    // will work as they both allow the system to free anonymous pages.
+    // It is important that we try both methods as the kernel which we were
+    // built on may differ from the kernel we are now running on.
     r = madvise(at, size, MADV_FREE);
-#else
-    r = madvise(at, size, MADV_DONTNEED);
+    if(r < 0) {
+        if (errno == EINVAL) {
+            // Perhaps the system doesn't support MADV_FREE; fall-through and
+            // try MADV_DONTNEED.
+        } else {
+            sysErrorBelch("unable to decommit memory");
+        }
+    } else {
+        return;
+    }
 #endif
+
+    r = madvise(at, size, MADV_DONTNEED);
     if(r < 0)
         sysErrorBelch("unable to decommit memory");
 }