[Qemu-devel] [PATCH V3 10/11] vcpu: introduce lockmap

[Liu Ping Fan <qemulist@gmail.com>]

From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>

The func call chain can suffer from recursively hold
qemu_mutex_lock_iothread. We introduce lockmap to record the
lock depth.

Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
---
 cpus.c              |   18 ++++++++++++++++++
 qemu-thread-posix.c |   23 +++++++++++++++++++++++
 qemu-thread-posix.h |    5 +++++
 qemu-thread.h       |    3 +++
 4 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/cpus.c b/cpus.c
index 4cd7f85..09f6670 100644
--- a/cpus.c
+++ b/cpus.c
@@ -736,6 +736,8 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
     int r;
 
     pthread_setspecific(qemu_thread_key, cpu->thread);
+    cpu->thread->lockmap.biglock = 0;
+    qemu_big_lockmap_inc();
     qemu_mutex_lock(&qemu_global_mutex);
     qemu_thread_get_self(cpu->thread);
     env->thread_id = qemu_get_thread_id();
@@ -905,6 +907,14 @@ int qemu_cpu_is_self(void *_env)
 
 void qemu_mutex_lock_iothread(void)
 {
+    unsigned int map;
+
+    if (!qemu_thread_is_self(&io_thread)) {
+        map = qemu_big_lockmap_inc();
+        if (map > 1) {
+            return;
+        }
+    }
     if (!tcg_enabled()) {
         qemu_mutex_lock(&qemu_global_mutex);
     } else {
@@ -920,6 +930,14 @@ void qemu_mutex_lock_iothread(void)
 
 void qemu_mutex_unlock_iothread(void)
 {
+    unsigned int map;
+
+    if (!qemu_thread_is_self(&io_thread)) {
+        map = qemu_big_lockmap_dec();
+        if (map != 0) {
+            return;
+        }
+    }
     qemu_mutex_unlock(&qemu_global_mutex);
 }
 
diff --git a/qemu-thread-posix.c b/qemu-thread-posix.c
index f448fcb..1e07dc2 100644
--- a/qemu-thread-posix.c
+++ b/qemu-thread-posix.c
@@ -17,6 +17,7 @@
 #include <signal.h>
 #include <stdint.h>
 #include <string.h>
+#include <glib.h>
 #include "qemu-thread.h"
 
 pthread_key_t qemu_thread_key;
@@ -158,6 +159,28 @@ void qemu_thread_key_create(void)
     pthread_key_create(&qemu_thread_key, NULL);
 }
 
+int16_t qemu_big_lockmap_inc(void)
+{
+    QemuThread *t = pthread_getspecific(qemu_thread_key);
+
+    return ++t->lockmap.biglock;
+}
+
+int16_t qemu_big_lockmap_dec(void)
+{
+    QemuThread *t = pthread_getspecific(qemu_thread_key);
+    g_assert(t->lockmap.biglock > 0);
+
+    return --t->lockmap.biglock;
+}
+
+int16_t qemu_big_lockmap_get(void)
+{
+    QemuThread *t = pthread_getspecific(qemu_thread_key);
+
+    return t->lockmap.biglock;
+}
+
 bool qemu_thread_is_self(QemuThread *thread)
 {
    return pthread_equal(pthread_self(), thread->thread);
diff --git a/qemu-thread-posix.h b/qemu-thread-posix.h
index 2607b1c..8f9506b 100644
--- a/qemu-thread-posix.h
+++ b/qemu-thread-posix.h
@@ -10,8 +10,13 @@ struct QemuCond {
     pthread_cond_t cond;
 };
 
+typedef struct Lockmap {
+    int16_t biglock;
+} Lockmap;
+
 struct QemuThread {
     pthread_t thread;
+    Lockmap lockmap;
 };
 
 extern pthread_key_t qemu_thread_key;
diff --git a/qemu-thread.h b/qemu-thread.h
index 4a6427d..529850b 100644
--- a/qemu-thread.h
+++ b/qemu-thread.h
@@ -47,4 +47,7 @@ bool qemu_thread_is_self(QemuThread *thread);
 void qemu_thread_exit(void *retval);
 
 void qemu_thread_key_create(void);
+int16_t qemu_big_lockmap_inc(void);
+int16_t qemu_big_lockmap_dec(void);
+int16_t qemu_big_lockmap_get(void);
 #endif
-- 
1.7.4.4