rcu: actually register threads that have RCU read-side critical sections

Otherwise, grace periods are detected too early!
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

cpus.c

@@ -954,6 +954,8 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
     CPUState *cpu = arg;
     int r;
 
+    rcu_register_thread();
+
     qemu_mutex_lock_iothread();
     qemu_thread_get_self(cpu->thread);
     cpu->thread_id = qemu_get_thread_id();
@@ -995,6 +997,8 @@ static void *qemu_dummy_cpu_thread_fn(void *arg)
     sigset_t waitset;
     int r;
 
+    rcu_register_thread();
+
     qemu_mutex_lock_iothread();
     qemu_thread_get_self(cpu->thread);
     cpu->thread_id = qemu_get_thread_id();
@@ -1034,6 +1038,8 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
 {
     CPUState *cpu = arg;
 
+    rcu_register_thread();
+
     qemu_mutex_lock_iothread();
     qemu_tcg_init_cpu_signals();
     qemu_thread_get_self(cpu->thread);

iothread.c

@@ -18,6 +18,7 @@
 #include "sysemu/iothread.h"
 #include "qmp-commands.h"
 #include "qemu/error-report.h"
+#include "qemu/rcu.h"
 
 typedef ObjectClass IOThreadClass;
 
@@ -31,6 +32,8 @@ static void *iothread_run(void *opaque)
     IOThread *iothread = opaque;
     bool blocking;
 
+    rcu_register_thread();
+
     qemu_mutex_lock(&iothread->init_done_lock);
     iothread->thread_id = qemu_get_thread_id();
     qemu_cond_signal(&iothread->init_done_cond);
@@ -45,6 +48,8 @@ static void *iothread_run(void *opaque)
         }
         aio_context_release(iothread->ctx);
     }
+
+    rcu_unregister_thread();
     return NULL;
 }
 

migration/migration.c

@@ -22,6 +22,7 @@
 #include "block/block.h"
 #include "qapi/qmp/qerror.h"
 #include "qemu/sockets.h"
+#include "qemu/rcu.h"
 #include "migration/block.h"
 #include "qemu/thread.h"
 #include "qmp-commands.h"
@@ -917,6 +918,8 @@ static void *migration_thread(void *opaque)
     int64_t start_time = initial_time;
     bool old_vm_running = false;
 
+    rcu_register_thread();
+
     qemu_savevm_state_header(s->file);
     qemu_savevm_state_begin(s->file, &s->params);
 
@@ -1016,6 +1019,7 @@ static void *migration_thread(void *opaque)
     qemu_bh_schedule(s->cleanup_bh);
     qemu_mutex_unlock_iothread();
 
+    rcu_unregister_thread();
     return NULL;
 }
 

tests/test-rcu-list.c

@@ -108,6 +108,8 @@ static void *rcu_q_reader(void *arg)
     long long n_reads_local = 0;
     struct list_element *el;
 
+    rcu_register_thread();
+
     *(struct rcu_reader_data **)arg = &rcu_reader;
     atomic_inc(&nthreadsrunning);
     while (goflag == GOFLAG_INIT) {
@@ -129,6 +131,8 @@ static void *rcu_q_reader(void *arg)
     qemu_mutex_lock(&counts_mutex);
     n_reads += n_reads_local;
     qemu_mutex_unlock(&counts_mutex);
+
+    rcu_unregister_thread();
     return NULL;
 }
 

util/rcu.c

@@ -216,6 +216,8 @@ static void *call_rcu_thread(void *opaque)
 {
     struct rcu_head *node;
 
+    rcu_register_thread();
+
     for (;;) {
         int tries = 0;
         int n = atomic_read(&rcu_call_count);