commit 068a5ea02f62853116788a2c42d8851a94bb7567
author Emilio G. Cota <cota@braap.org> Sun Aug 19 05:13:35 2018 -0400
committer Paolo Bonzini <pbonzini@redhat.com> Thu Aug 23 18:46:25 2018 +0200
tree 0e7c635241a440b1aeee6dd853077fad928a40d4
parent 04d595b300041bec645c862baccbea1c8befb6d4

qom: convert the CPU list to RCU

Iterating over the list without using atomics is undefined behaviour,
since the list can be modified concurrently by other threads (e.g.
every time a new thread is created in user-mode).

Fix it by implementing the CPU list as an RCU QTAILQ. This requires
a little bit of extra work to traverse list in reverse order (see
previous patch), but other than that the conversion is trivial.

Signed-off-by: Emilio G. Cota <cota@braap.org>
Message-Id: <20180819091335.22863-12-cota@braap.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

linux-user/syscall.c

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 202aa77..3c3c1ae 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -8157,7 +8157,7 @@
             TaskState *ts;
 
             /* Remove the CPU from the list.  */
-            QTAILQ_REMOVE(&cpus, cpu, node);
+            QTAILQ_REMOVE_RCU(&cpus, cpu, node);
 
             cpu_list_unlock();