[Qemu-devel] [RFC v2 09/11] linux-user: Support CPU work queue

[Sergey Fedorov]

From: Sergey Fedorov <address@hidden>

Make CPU work core functions common between system and user-mode
emulation. User-mode does not have BQL, so process_queued_cpu_work() is
protected by 'exclusive_lock'.

Signed-off-by: Sergey Fedorov <address@hidden>
Signed-off-by: Sergey Fedorov <address@hidden>
---

Changes in v2:
 - 'qemu_work_cond' definition moved to cpu-exec-common.c
 - documentation commend for new public API added

---
 cpu-exec-common.c       | 85 ++++++++++++++++++++++++++++++++++++++++++++++++
 cpus.c                  | 86 +------------------------------------------------
 include/exec/exec-all.h | 17 ++++++++++
 linux-user/main.c       |  8 +++++
 4 files changed, 111 insertions(+), 85 deletions(-)

diff --git a/cpu-exec-common.c b/cpu-exec-common.c
index 0cb4ae60eff9..a233f0124559 100644
--- a/cpu-exec-common.c
+++ b/cpu-exec-common.c
@@ -77,3 +77,88 @@ void cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc)
     }
     siglongjmp(cpu->jmp_env, 1);
 }
+
+QemuCond qemu_work_cond;
+
+static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi)
+{
+    qemu_mutex_lock(&cpu->work_mutex);
+    if (cpu->queued_work_first == NULL) {
+        cpu->queued_work_first = wi;
+    } else {
+        cpu->queued_work_last->next = wi;
+    }
+    cpu->queued_work_last = wi;
+    wi->next = NULL;
+    wi->done = false;
+    qemu_mutex_unlock(&cpu->work_mutex);
+
+    qemu_cpu_kick(cpu);
+}
+
+void run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
+{
+    struct qemu_work_item wi;
+
+    if (qemu_cpu_is_self(cpu)) {
+        func(cpu, data);
+        return;
+    }
+
+    wi.func = func;
+    wi.data = data;
+    wi.free = false;
+
+    queue_work_on_cpu(cpu, &wi);
+    while (!atomic_mb_read(&wi.done)) {
+        CPUState *self_cpu = current_cpu;
+
+        qemu_cond_wait(&qemu_work_cond, qemu_get_cpu_work_mutex());
+        current_cpu = self_cpu;
+    }
+}
+
+void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
+{
+    struct qemu_work_item *wi;
+
+    if (qemu_cpu_is_self(cpu)) {
+        func(cpu, data);
+        return;
+    }
+
+    wi = g_malloc0(sizeof(struct qemu_work_item));
+    wi->func = func;
+    wi->data = data;
+    wi->free = true;
+
+    queue_work_on_cpu(cpu, wi);
+}
+
+void process_queued_cpu_work(CPUState *cpu)
+{
+    struct qemu_work_item *wi;
+
+    if (cpu->queued_work_first == NULL) {
+        return;
+    }
+
+    qemu_mutex_lock(&cpu->work_mutex);
+    while (cpu->queued_work_first != NULL) {
+        wi = cpu->queued_work_first;
+        cpu->queued_work_first = wi->next;
+        if (!cpu->queued_work_first) {
+            cpu->queued_work_last = NULL;
+        }
+        qemu_mutex_unlock(&cpu->work_mutex);
+        wi->func(cpu, wi->data);
+        qemu_mutex_lock(&cpu->work_mutex);
+        if (wi->free) {
+            g_free(wi);
+        } else {
+            atomic_mb_set(&wi->done, true);
+        }
+    }
+    qemu_mutex_unlock(&cpu->work_mutex);
+    qemu_cond_broadcast(&qemu_work_cond);
+}
diff --git a/cpus.c b/cpus.c
index 51fd8c18b4c8..282d7e399902 100644
--- a/cpus.c
+++ b/cpus.c
@@ -896,7 +896,6 @@ static QemuThread io_thread;
 static QemuCond qemu_cpu_cond;
 /* system init */
 static QemuCond qemu_pause_cond;
-static QemuCond qemu_work_cond;
 
 void qemu_init_cpu_loop(void)
 {
@@ -910,66 +909,11 @@ void qemu_init_cpu_loop(void)
     qemu_thread_get_self(&io_thread);
 }
 
-static QemuMutex *qemu_get_cpu_work_mutex(void)
+QemuMutex *qemu_get_cpu_work_mutex(void)
 {
     return &qemu_global_mutex;
 }
 
-static void queue_work_on_cpu(CPUState *cpu, struct qemu_work_item *wi)
-{
-    qemu_mutex_lock(&cpu->work_mutex);
-    if (cpu->queued_work_first == NULL) {
-        cpu->queued_work_first = wi;
-    } else {
-        cpu->queued_work_last->next = wi;
-    }
-    cpu->queued_work_last = wi;
-    wi->next = NULL;
-    wi->done = false;
-    qemu_mutex_unlock(&cpu->work_mutex);
-
-    qemu_cpu_kick(cpu);
-}
-
-void run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
-{
-    struct qemu_work_item wi;
-
-    if (qemu_cpu_is_self(cpu)) {
-        func(cpu, data);
-        return;
-    }
-
-    wi.func = func;
-    wi.data = data;
-    wi.free = false;
-
-    queue_work_on_cpu(cpu, &wi);
-    while (!atomic_mb_read(&wi.done)) {
-        CPUState *self_cpu = current_cpu;
-
-        qemu_cond_wait(&qemu_work_cond, qemu_get_cpu_work_mutex());
-        current_cpu = self_cpu;
-    }
-}
-
-void async_run_on_cpu(CPUState *cpu, run_on_cpu_func func, void *data)
-{
-    struct qemu_work_item *wi;
-
-    if (qemu_cpu_is_self(cpu)) {
-        func(cpu, data);
-        return;
-    }
-
-    wi = g_malloc0(sizeof(struct qemu_work_item));
-    wi->func = func;
-    wi->data = data;
-    wi->free = true;
-
-    queue_work_on_cpu(cpu, wi);
-}
-
 static void qemu_kvm_destroy_vcpu(CPUState *cpu)
 {
     if (kvm_destroy_vcpu(cpu) < 0) {
@@ -982,34 +926,6 @@ static void qemu_tcg_destroy_vcpu(CPUState *cpu)
 {
 }
 
-static void process_queued_cpu_work(CPUState *cpu)
-{
-    struct qemu_work_item *wi;
-
-    if (cpu->queued_work_first == NULL) {
-        return;
-    }
-
-    qemu_mutex_lock(&cpu->work_mutex);
-    while (cpu->queued_work_first != NULL) {
-        wi = cpu->queued_work_first;
-        cpu->queued_work_first = wi->next;
-        if (!cpu->queued_work_first) {
-            cpu->queued_work_last = NULL;
-        }
-        qemu_mutex_unlock(&cpu->work_mutex);
-        wi->func(cpu, wi->data);
-        qemu_mutex_lock(&cpu->work_mutex);
-        if (wi->free) {
-            g_free(wi);
-        } else {
-            atomic_mb_set(&wi->done, true);
-        }
-    }
-    qemu_mutex_unlock(&cpu->work_mutex);
-    qemu_cond_broadcast(&qemu_work_cond);
-}
-
 static void qemu_wait_io_event_common(CPUState *cpu)
 {
     if (cpu->stop) {
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index c1f59fa59d2c..bceecbd5222a 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -407,4 +407,21 @@ extern int singlestep;
 extern CPUState *tcg_current_cpu;
 extern bool exit_request;
 
+/**
+ * qemu_work_cond - condition to wait for CPU work items completion
+ */
+extern QemuCond qemu_work_cond;
+
+/**
+ * qemu_get_cpu_work_mutex() - get the mutex which protects CPU work execution
+ *
+ * Return: A pointer to the mutex.
+ */
+QemuMutex *qemu_get_cpu_work_mutex(void);
+/**
+ * process_queued_cpu_work() - process all items on CPU work queue
+ * @cpu: The CPU which work queue to process.
+ */
+void process_queued_cpu_work(CPUState *cpu);
+
 #endif
diff --git a/linux-user/main.c b/linux-user/main.c
index a8790ac63f68..fce61d5a35fc 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -121,6 +121,7 @@ void qemu_init_cpu_loop(void)
     qemu_mutex_init(&exclusive_lock);
     qemu_cond_init(&exclusive_cond);
     qemu_cond_init(&exclusive_resume);
+    qemu_cond_init(&qemu_work_cond);
 }
 
 /* Make sure everything is in a consistent state for calling fork().  */
@@ -149,6 +150,7 @@ void fork_end(int child)
         qemu_mutex_init(&cpu_list_mutex);
         qemu_cond_init(&exclusive_cond);
         qemu_cond_init(&exclusive_resume);
+        qemu_cond_init(&qemu_work_cond);
         qemu_mutex_init(&tcg_ctx.tb_ctx.tb_lock);
         gdbserver_fork(thread_cpu);
     } else {
@@ -157,6 +159,11 @@ void fork_end(int child)
     }
 }
 
+QemuMutex *qemu_get_cpu_work_mutex(void)
+{
+    return &exclusive_lock;
+}
+
 /* Wait for pending exclusive operations to complete.  The exclusive lock
    must be held.  */
 static inline void exclusive_idle(void)
@@ -215,6 +222,7 @@ static inline void cpu_exec_end(CPUState *cpu)
         qemu_cond_signal(&exclusive_cond);
     }
     exclusive_idle();
+    process_queued_cpu_work(cpu);
     qemu_mutex_unlock(&exclusive_lock);
 }
 
-- 
1.9.1