[PATCH 11/19] accel/tcg: Fixed tsan warnings related to parallel_cpus

[Robert Foley]

Fixed several tsan warnings. e.g.

WARNING: ThreadSanitizer: data race (pid=35425)
  Read of size 1 at 0x557cd83aee28 by thread T7:
    #0 curr_cflags include/exec/exec-all.h:460:13 (qemu-system-aarch64+0x4b7f27)
    #1 cpu_exec accel/tcg/cpu-exec.c:730:26 (qemu-system-aarch64+0x4b7f27)
    #2 tcg_cpu_exec cpus.c:1415:11 (qemu-system-aarch64+0x45b9b6)
    #3 qemu_tcg_cpu_thread_fn cpus.c:1723:17 (qemu-system-aarch64+0x45b9b6)
    #4 qemu_thread_start util/qemu-thread-posix.c:519:9 
(qemu-system-aarch64+0xd431e0)

  Previous write of size 1 at 0x557cd83aee28 by thread T6:
    #0 cpu_exec_step_atomic accel/tcg/cpu-exec.c:254:23 
(qemu-system-aarch64+0x4b6caa)
    #1 qemu_tcg_cpu_thread_fn cpus.c:1741:17 (qemu-system-aarch64+0x45baca)
    #2 qemu_thread_start util/qemu-thread-posix.c:519:9 
(qemu-system-aarch64+0xd431e0)

  Location is global 'parallel_cpus' of size 1 at 0x557cd83aee28 
(qemu-system-aarch64+0x000001fb3e28)

Cc: Richard Henderson <address@hidden>
Cc: Paolo Bonzini <address@hidden>
Signed-off-by: Robert Foley <address@hidden>
---
 accel/tcg/cpu-exec.c    | 4 ++--
 cpus.c                  | 2 +-
 include/exec/exec-all.h | 2 +-
 linux-user/syscall.c    | 4 ++--
 4 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index d95c4848a4..4cbdef1373 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -250,7 +250,7 @@ void cpu_exec_step_atomic(CPUState *cpu)
         }
 
         /* Since we got here, we know that parallel_cpus must be true.  */
-        parallel_cpus = false;
+        atomic_set(&parallel_cpus, false);
         cc->cpu_exec_enter(cpu);
         /* execute the generated code */
         trace_exec_tb(tb, pc);
@@ -278,7 +278,7 @@ void cpu_exec_step_atomic(CPUState *cpu)
      * the execution.
      */
     g_assert(cpu_in_exclusive_context(cpu));
-    parallel_cpus = true;
+    atomic_set(&parallel_cpus, true);
     end_exclusive();
 }
 
diff --git a/cpus.c b/cpus.c
index af44027549..c5d04486a8 100644
--- a/cpus.c
+++ b/cpus.c
@@ -1966,7 +1966,7 @@ static void qemu_tcg_init_vcpu(CPUState *cpu)
 
         if (qemu_tcg_mttcg_enabled()) {
             /* create a thread per vCPU with TCG (MTTCG) */
-            parallel_cpus = true;
+            atomic_set(&parallel_cpus, true);
             snprintf(thread_name, VCPU_THREAD_NAME_SIZE, "CPU %d/TCG",
                  cpu->cpu_index);
 
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 3cf88272df..3f2c0290e1 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -496,7 +496,7 @@ static inline uint32_t tb_cflags(const TranslationBlock *tb)
 /* current cflags for hashing/comparison */
 static inline uint32_t curr_cflags(void)
 {
-    return (parallel_cpus ? CF_PARALLEL : 0)
+    return (atomic_read(&parallel_cpus) ? CF_PARALLEL : 0)
          | (use_icount ? CF_USE_ICOUNT : 0);
 }
 
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 05f03919ff..8e39c09c5d 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6022,8 +6022,8 @@ static int do_fork(CPUArchState *env, unsigned int flags, 
abi_ulong newsp,
         /* If this is our first additional thread, we need to ensure we
          * generate code for parallel execution and flush old translations.
          */
-        if (!parallel_cpus) {
-            parallel_cpus = true;
+        if (!atomic_read(&parallel_cpus)) {
+            atomic_set(&parallel_cpus, true);
             tb_flush(cpu);
         }
 
-- 
2.17.1