From: Alex Bennée <alex.bennee@linaro.org>
Date: Fri, 21 Oct 2016 15:34:18 +0000 (+0100)
Subject: exec.c: ensure all AddressSpaceDispatch updates under RCU
X-Git-Tag: qemu-xen-4.9.0-rc1~88^2~25
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=f35e44e7645edbb08e35b111c10c2fc57e2905c7;p=qemu-xen.git

exec.c: ensure all AddressSpaceDispatch updates under RCU

The memory_dispatch field is meant to be protected by RCU so we should
use the correct primitives when accessing it. This race was flagged up
by the ThreadSanitizer.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20161021153418.21571-1-alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/exec.c b/exec.c
index 4d085812ca..a19ed21bff 100644
--- a/exec.c
+++ b/exec.c
@@ -493,7 +493,7 @@ address_space_translate_for_iotlb(CPUState *cpu, int asidx, hwaddr addr,
                                   hwaddr *xlat, hwaddr *plen)
 {
     MemoryRegionSection *section;
-    AddressSpaceDispatch *d = cpu->cpu_ases[asidx].memory_dispatch;
+    AddressSpaceDispatch *d = atomic_rcu_read(&cpu->cpu_ases[asidx].memory_dispatch);
 
     section = address_space_translate_internal(d, addr, xlat, plen, false);
 
@@ -2376,7 +2376,7 @@ static void tcg_commit(MemoryListener *listener)
      * may have split the RCU critical section.
      */
     d = atomic_rcu_read(&cpuas->as->dispatch);
-    cpuas->memory_dispatch = d;
+    atomic_rcu_set(&cpuas->memory_dispatch, d);
     tlb_flush(cpuas->cpu, 1);
 }