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

* --help/--version improvements (Eric)
* GCC 7 workaround (Greg)
* Small SCSI fix (Hannes)
* SSE 4.1 fix (Joseph)
* RCU deadlock fix (myself)

# gpg: Signature made Tue 08 Aug 2017 16:28:56 BST
# gpg:                using RSA key 0xBFFBD25F78C7AE83
# 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:
  maint: Include bug-reporting info in --help output
  qga: Give more --version information
  qemu-io: Give more --version information
  qemu-img: Sort sub-command names in --help
  target/i386: set rip_offset for some SSE4.1 instructions
  scsi: clarify sense codes for LUN0 emulation
  kvm: workaround build break on gcc-7.1.1 / fedora26
  Revert "rcu: do not create thread in pthread_atfork callback"
  rcu: completely disable pthread_atfork callbacks as soon as possible

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

1 files changed, 27 insertions, 3 deletions

diff --git a/util/rcu.c b/util/rcu.c
index 9adc5e4a36..ca5a63e36a 100644
--- a/util/rcu.c
+++ b/util/rcu.c
@@ -318,30 +318,54 @@ static void rcu_init_complete(void)
     rcu_register_thread();
 }
 
+static int atfork_depth = 1;
+
+void rcu_enable_atfork(void)
+{
+    atfork_depth++;
+}
+
+void rcu_disable_atfork(void)
+{
+    atfork_depth--;
+}
+
 #ifdef CONFIG_POSIX
 static void rcu_init_lock(void)
 {
+    if (atfork_depth < 1) {
+        return;
+    }
+
     qemu_mutex_lock(&rcu_sync_lock);
     qemu_mutex_lock(&rcu_registry_lock);
 }
 
 static void rcu_init_unlock(void)
 {
+    if (atfork_depth < 1) {
+        return;
+    }
+
     qemu_mutex_unlock(&rcu_registry_lock);
     qemu_mutex_unlock(&rcu_sync_lock);
 }
-#endif
 
-void rcu_after_fork(void)
+static void rcu_init_child(void)
 {
+    if (atfork_depth < 1) {
+        return;
+    }
+
     memset(&registry, 0, sizeof(registry));
     rcu_init_complete();
 }
+#endif
 
 static void __attribute__((__constructor__)) rcu_init(void)
 {
 #ifdef CONFIG_POSIX
-    pthread_atfork(rcu_init_lock, rcu_init_unlock, rcu_init_unlock);
+    pthread_atfork(rcu_init_lock, rcu_init_unlock, rcu_init_child);
 #endif
     rcu_init_complete();
 }