accel/tcg: Add cpu_in_serial_context

Like cpu_in_exclusive_context, but also true if
there is no other cpu against which we could race.

Use it in tb_flush as a direct replacement.
Use it in cpu_loop_exit_atomic to ensure that there
is no loop against cpu_exec_step_atomic.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/accel/tcg/cpu-exec-common.c b/accel/tcg/cpu-exec-common.c
index e7962c9348..9a5fabf625 100644
--- a/accel/tcg/cpu-exec-common.c
+++ b/accel/tcg/cpu-exec-common.c
@@ -22,6 +22,7 @@
 #include "sysemu/tcg.h"
 #include "exec/exec-all.h"
 #include "qemu/plugin.h"
+#include "internal.h"
 
 bool tcg_allowed;
 
@@ -81,6 +82,8 @@ void cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc)
 
 void cpu_loop_exit_atomic(CPUState *cpu, uintptr_t pc)
 {
+    /* Prevent looping if already executing in a serial context. */
+    g_assert(!cpu_in_serial_context(cpu));
     cpu->exception_index = EXCP_ATOMIC;
     cpu_loop_exit_restore(cpu, pc);
 }