[PATCH v2 03/30] accel/tcg: Add cpu_in_serial_context

[Richard Henderson <richard.henderson@linaro.org>]

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.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 accel/tcg/internal.h        | 5 +++++
 accel/tcg/cpu-exec-common.c | 3 +++
 accel/tcg/tb-maint.c        | 2 +-
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/accel/tcg/internal.h b/accel/tcg/internal.h
index 6edff16fb0..e181872a93 100644
--- a/accel/tcg/internal.h
+++ b/accel/tcg/internal.h
@@ -64,4 +64,9 @@ static inline target_ulong log_pc(CPUState *cpu, const TranslationBlock *tb)
 #endif
 }
 
+static inline bool cpu_in_serial_context(CPUState *cs)
+{
+    return !(cs->tcg_cflags & CF_PARALLEL) || cpu_in_exclusive_context(cs);
+}
+
 #endif /* ACCEL_TCG_INTERNAL_H */
diff --git a/accel/tcg/cpu-exec-common.c b/accel/tcg/cpu-exec-common.c
index c7bc8c6efa..2fb4454c7a 100644
--- a/accel/tcg/cpu-exec-common.c
+++ b/accel/tcg/cpu-exec-common.c
@@ -21,6 +21,7 @@
 #include "sysemu/cpus.h"
 #include "sysemu/tcg.h"
 #include "exec/exec-all.h"
+#include "internal.h"
 
 bool tcg_allowed;
 
@@ -78,6 +79,8 @@ 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);
 }
diff --git a/accel/tcg/tb-maint.c b/accel/tcg/tb-maint.c
index b3d6529ae2..4f6b447149 100644
--- a/accel/tcg/tb-maint.c
+++ b/accel/tcg/tb-maint.c
@@ -758,7 +758,7 @@ void tb_flush(CPUState *cpu)
     if (tcg_enabled()) {
         unsigned tb_flush_count = qatomic_mb_read(&tb_ctx.tb_flush_count);
 
-        if (cpu_in_exclusive_context(cpu)) {
+        if (cpu_in_serial_context(cpu)) {
             do_tb_flush(cpu, RUN_ON_CPU_HOST_INT(tb_flush_count));
         } else {
             async_safe_run_on_cpu(cpu, do_tb_flush,
-- 
2.34.1