Re: [PATCH v3 57/68] accel/tcg: Expose vcpu_[un]register() for MTTCG

[Richard Henderson]

On 7/1/25 08:40, Philippe Mathieu-Daudé wrote:

Allocate ForceRcuNotifier on the Heap.

Signed-off-by: Philippe Mathieu-Daudé <phi...@linaro.org>
---
  accel/tcg/tcg-accel-ops-mttcg.c | 30 ++++++++++++++++++++++++------
  1 file changed, 24 insertions(+), 6 deletions(-)

Please document the motivation.

r~

diff --git a/accel/tcg/tcg-accel-ops-mttcg.c b/accel/tcg/tcg-accel-ops-mttcg.c
index 4de506a80ca..2d31b00ee59 100644
--- a/accel/tcg/tcg-accel-ops-mttcg.c
+++ b/accel/tcg/tcg-accel-ops-mttcg.c
@@ -55,6 +55,27 @@ static void mttcg_force_rcu(Notifier *notify, void *data)
      async_run_on_cpu(cpu, do_nothing, RUN_ON_CPU_NULL);
  }

+static void *mttcg_vcpu_register(CPUState *cpu)

+{
+    MttcgForceRcuNotifier *force_rcu = g_new(MttcgForceRcuNotifier, 1);
+
+    force_rcu->notifier.notify = mttcg_force_rcu;
+    force_rcu->cpu = cpu;
+    rcu_add_force_rcu_notifier(&force_rcu->notifier);
+    tcg_register_thread();
+
+    return force_rcu;
+}
+
+static void mttcg_vcpu_unregister(CPUState *cpu, void *opaque)
+{
+    MttcgForceRcuNotifier *force_rcu = opaque;
+
+    rcu_remove_force_rcu_notifier(&force_rcu->notifier);
+
+    g_free(force_rcu);
+}
+
  /*
   * In the multi-threaded case each vCPU has its own thread. The TLS
   * variable current_cpu can be used deep in the code to find the
@@ -63,17 +84,14 @@ static void mttcg_force_rcu(Notifier *notify, void *data)

void *mttcg_cpu_thread_routine(void *arg)

  {
-    MttcgForceRcuNotifier force_rcu;
+    MttcgForceRcuNotifier *force_rcu;
      CPUState *cpu = arg;

assert(tcg_enabled());

      g_assert(!icount_enabled());

rcu_register_thread();

-    force_rcu.notifier.notify = mttcg_force_rcu;
-    force_rcu.cpu = cpu;
-    rcu_add_force_rcu_notifier(&force_rcu.notifier);
-    tcg_register_thread();
+    force_rcu = mttcg_vcpu_register(cpu);

bql_lock();

      qemu_thread_get_self(cpu->thread);
@@ -121,7 +139,7 @@ void *mttcg_cpu_thread_routine(void *arg)

tcg_cpu_destroy(cpu);

      bql_unlock();
-    rcu_remove_force_rcu_notifier(&force_rcu.notifier);
+    mttcg_vcpu_unregister(cpu, force_rcu);
      rcu_unregister_thread();
      return NULL;
  }