Merge remote-tracking branch 'remotes/bonzini/tags/for-upstream' into staging

* Record-replay lockstep execution, log dumper and fixes (Alex, Pavel)
* SCSI fix to pass maximum transfer size (Daniel Barboza)
* chardev fixes and improved iothread support (Daniel Berrangé, Peter)
* checkpatch tweak (Eric)
* make help tweak (Marc-André)
* make more PCI NICs available with -net or -nic (myself)
* change default q35 NIC to e1000e (myself)
* SCSI support for NDOB bit (myself)
* membarrier system call support (myself)
* SuperIO refactoring (Philippe)
* miscellaneous cleanups and fixes (Thomas)

# gpg: Signature made Mon 12 Mar 2018 16:10:52 GMT
# gpg:                using RSA key BFFBD25F78C7AE83
# gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>"
# gpg:                 aka "Paolo Bonzini <pbonzini@redhat.com>"
# Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4  E2F7 7E15 100C CD36 69B1
#      Subkey fingerprint: F133 3857 4B66 2389 866C  7682 BFFB D25F 78C7 AE83

* remotes/bonzini/tags/for-upstream: (69 commits)
  tcg: fix cpu_io_recompile
  replay: update documentation
  replay: save vmstate of the asynchronous events
  replay: don't process async events when warping the clock
  scripts/replay-dump.py: replay log dumper
  replay: avoid recursive call of checkpoints
  replay: check return values of fwrite
  replay: push replay_mutex_lock up the call tree
  replay: don't destroy mutex at exit
  replay: make locking visible outside replay code
  replay/replay-internal.c: track holding of replay_lock
  replay/replay.c: bump REPLAY_VERSION again
  replay: save prior value of the host clock
  replay: added replay log format description
  replay: fix save/load vm for non-empty queue
  replay: fixed replay_enable_events
  replay: fix processing async events
  cpu-exec: fix exception_index handling
  hw/i386/pc: Factor out the superio code
  hw/alpha/dp264: Use the TYPE_SMC37C669_SUPERIO
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

# Conflicts:
#	default-configs/i386-softmmu.mak
#	default-configs/x86_64-softmmu.mak

1 files changed, 11 insertions, 4 deletions

diff --git a/util/rcu.c b/util/rcu.c
index f4d09c8304..5676c22bd1 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -92,10 +92,11 @@ static void wait_for_readers(void)
             atomic_set(&index->waiting, true);
         }
 
-        /* Here, order the stores to index->waiting before the
-         * loads of index->ctr.
+        /* Here, order the stores to index->waiting before the loads of
+         * index->ctr.  Pairs with smp_mb_placeholder() in rcu_read_unlock(),
+         * ensuring that the loads of index->ctr are sequentially consistent.
          */
-        smp_mb();
+        smp_mb_global();
 
         QLIST_FOREACH_SAFE(index, &registry, node, tmp) {
             if (!rcu_gp_ongoing(&index->ctr)) {
@@ -142,8 +143,13 @@ static void wait_for_readers(void)
 void synchronize_rcu(void)
 {
     qemu_mutex_lock(&rcu_sync_lock);
-    qemu_mutex_lock(&rcu_registry_lock);
 
+    /* Write RCU-protected pointers before reading p_rcu_reader->ctr.
+     * Pairs with smp_mb_placeholder() in rcu_read_lock().
+     */
+    smp_mb_global();
+
+    qemu_mutex_lock(&rcu_registry_lock);
     if (!QLIST_EMPTY(&registry)) {
         /* In either case, the atomic_mb_set below blocks stores that free
          * old RCU-protected pointers.
@@ -370,6 +376,7 @@ static void rcu_init_child(void)
 
 static void __attribute__((__constructor__)) rcu_init(void)
 {
+    smp_mb_global_init();
 #ifdef CONFIG_POSIX
     pthread_atfork(rcu_init_lock, rcu_init_unlock, rcu_init_child);
 #endif