[Qemu-devel] [PATCH 11/12] Threadlets: Add functionality to create private queues.

[Qemu-devel] [PATCH 11/12] Threadlets: Add functionality to create private queues.

[Arun R Bharadwaj]

This patch allows subsystems to create their own private
queues with associated pools of threads.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
---
 qemu-threadlets.c |   75 ++++++++++++++++++++++++++++++++++++++---------------
 qemu-threadlets.h |    4 +++
 2 files changed, 58 insertions(+), 21 deletions(-)

diff --git a/qemu-threadlets.c b/qemu-threadlets.c
index 42dd3d1..4df79b8 100644
--- a/qemu-threadlets.c
+++ b/qemu-threadlets.c
@@ -99,6 +99,25 @@ static void spawn_threadlet(ThreadletQueue *queue)
 }
 
 /**
+ * submit_work_to_queue: Submit a new task to a private queue to be
+ *                            executed asynchronously.
+ * @queue: Per-subsystem private queue to which the new task needs
+ *         to be submitted.
+ * @work: Contains information about the task that needs to be submitted.
+ */
+void submit_work_to_queue(ThreadletQueue *queue, ThreadletWork *work)
+{
+    qemu_mutex_lock(&queue->lock);
+    if (queue->idle_threads == 0 && queue->cur_threads < queue->max_threads) {
+        spawn_threadlet(queue);
+    } else {
+        qemu_cond_signal(&queue->cond);
+    }
+    QTAILQ_INSERT_TAIL(&queue->request_list, work, node);
+    qemu_mutex_unlock(&queue->lock);
+}
+
+/**
  * submit_work: Submit to the global queue a new task to be executed
  *                   asynchronously.
  * @work: Contains information about the task that needs to be submitted.
@@ -106,26 +125,26 @@ static void spawn_threadlet(ThreadletQueue *queue)
 void submit_work(ThreadletWork *work)
 {
     if (!globalqueue_init) {
-        globalqueue.cur_threads  = 0;
-        globalqueue.idle_threads = 0;
-        globalqueue.max_threads = MAX_GLOBAL_THREADS;
-        globalqueue.min_threads = MIN_GLOBAL_THREADS;
-        QTAILQ_INIT(&globalqueue.request_list);
-        qemu_mutex_init(&globalqueue.lock);
-        qemu_cond_init(&globalqueue.cond);
-
+        threadlet_queue_init(&globalqueue, MAX_GLOBAL_THREADS,
+                                MIN_GLOBAL_THREADS);
         globalqueue_init = 1;
     }
 
-    qemu_mutex_lock(&globalqueue.lock);
-    if (globalqueue.idle_threads == 0 &&
-        globalqueue.cur_threads < globalqueue.max_threads) {
-        spawn_threadlet(&globalqueue);
-    } else {
-        qemu_cond_signal(&globalqueue.cond);
-    }
-    QTAILQ_INSERT_TAIL(&globalqueue.request_list, work, node);
-    qemu_mutex_unlock(&globalqueue.lock);
+    submit_work_to_queue(&globalqueue, work);
+}
+
+/**
+ * dequeue_work_on_queue: Cancel a task queued on a Queue.
+ * @queue: The queue containing the task to be cancelled.
+ * @work: Contains the information of the task that needs to be cancelled.
+ */
+int dequeue_work_on_queue(ThreadletQueue *queue, ThreadletWork *work)
+{
+    qemu_mutex_lock(&queue->lock);
+    QTAILQ_REMOVE(&queue->request_list, work, node);
+    qemu_mutex_unlock(&queue->lock);
+
+    return 0;
 }
 
 /**
@@ -134,9 +153,23 @@ void submit_work(ThreadletWork *work)
  */
 int dequeue_work(ThreadletWork *work)
 {
-    qemu_mutex_lock(&globalqueue.lock);
-    QTAILQ_REMOVE(&globalqueue.request_list, work, node);
-    qemu_mutex_unlock(&globalqueue.lock);
+    return dequeue_work_on_queue(&globalqueue, work);
+}
 
-    return 0;
+/**
+ * threadlet_queue_init: Initialize a threadlet queue.
+ * @queue: The threadlet queue to be initialized.
+ * @max_threads: Maximum number of threads processing the queue.
+ * @min_threads: Minimum number of threads processing the queue.
+ */
+void threadlet_queue_init(ThreadletQueue *queue,
+                                    int max_threads, int min_threads)
+{
+    queue->cur_threads  = 0;
+    queue->idle_threads = 0;
+    queue->max_threads  = max_threads;
+    queue->min_threads  = min_threads;
+    QTAILQ_INIT(&queue->request_list);
+    qemu_mutex_init(&queue->lock);
+    qemu_cond_init(&queue->cond);
 }
diff --git a/qemu-threadlets.h b/qemu-threadlets.h
index 03bb86b..993d7ab 100644
--- a/qemu-threadlets.h
+++ b/qemu-threadlets.h
@@ -37,7 +37,11 @@ typedef struct ThreadletWork
     void (*func)(struct ThreadletWork *work);
 } ThreadletWork;
 
+void submit_work_to_queue(ThreadletQueue *queue, ThreadletWork *work);
 void submit_work(ThreadletWork *work);
+int dequeue_work_on_queue(ThreadletQueue *queue, ThreadletWork *work);
 int dequeue_work(ThreadletWork *work);
 void threadlet_init(void);
+void threadlet_queue_init(ThreadletQueue *queue, int max_threads,
+                          int min_threads);
 #endif

[Qemu-devel] [PATCH 00/12] Threadlet Infrastructure

[Arun R Bharadwaj]

Hi,

This patch series introduces threadlet framework
in qemu.

Changelog:

* Modified the dequeue_work function logic which was
  earlier wrong. It now returns 0 on success and 1 on
  failure.

* removed the locking for container_of which is not 
  needed in handle_work()

* changed qemu-threadlets.[c|h] to qemu-threadlet.[c|h]

* introduced signal handler APIs in qemu-threadlet.c
  directly instead of in posix-aio-compat.c

Testing:

* I have tested this series using fsstress.
  Detailed testing information has been mentioned in the
  previous iteration.

The following series implements...

---

Arun R Bharadwaj (12):
      Add aiocb_mutex and aiocb_completion.
      Introduce work concept in posix-aio-compat.c
      Add callback function to ThreadletWork structure.
      Add ThreadletQueue.
      Threadlet: Add submit_work threadlet API.
      Threadlet: Add dequeue_work threadlet API and remove active field.
      Remove thread_create routine.
      Threadlet: Add aio_signal_handler threadlet API
      Remove all instances of CONFIG_THREAD
      Move threadlet code to qemu-threadlets.c
      Threadlets: Add functionality to create private queues.
      Threadlets: Add documentation


 Makefile.objs          |    3 -
 configure              |    2 
 docs/async-support.txt |  141 ++++++++++++++++++++++++++++
 posix-aio-compat.c     |  238 ++++++++++++------------------------------------
 qemu-threadlet.c       |  187 ++++++++++++++++++++++++++++++++++++++
 qemu-threadlet.h       |   48 ++++++++++
 vl.c                   |    3 +
 7 files changed, 440 insertions(+), 182 deletions(-)
 create mode 100644 docs/async-support.txt
 create mode 100644 qemu-threadlet.c
 create mode 100644 qemu-threadlet.h

-- 
arun

[Qemu-devel] [PATCH 01/12] Add aiocb_mutex and aiocb_completion.

[Arun R Bharadwaj]

This patch adds the aiocb_mutex to protect aiocb.
This patch also removes the infinite loop present in paio_cancel.

Since there can only be one cancellation at a time, we need to
introduce a condition variable. For this, we need a
global aiocb_completion condition variable.

This patch also adds the Makefile entry to compile qemu-thread.c
when CONFIG_POSIX is set, instead of the unused CONFIG_THREAD.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 Makefile.objs      |    2 +-
 posix-aio-compat.c |   39 ++++++++++++++++++++++++++++-----------
 2 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/Makefile.objs b/Makefile.objs
index cd5a24b..3b7ec27 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -9,6 +9,7 @@ qobject-obj-y += qerror.o
 
 block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
 block-obj-y += nbd.o block.o aio.o aes.o osdep.o qemu-config.o
+block-obj-$(CONFIG_POSIX) += qemu-thread.o
 block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
 block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
 
@@ -124,7 +125,6 @@ endif
 common-obj-y += $(addprefix ui/, $(ui-obj-y))
 
 common-obj-y += iov.o acl.o
-common-obj-$(CONFIG_THREAD) += qemu-thread.o
 common-obj-y += notify.o event_notifier.o
 common-obj-y += qemu-timer.o
 
diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 7b862b5..82862ec 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -27,9 +27,12 @@
 #include "qemu-common.h"
 #include "trace.h"
 #include "block_int.h"
+#include "qemu-thread.h"
 
 #include "block/raw-posix-aio.h"
 
+static QemuMutex aiocb_mutex;
+static QemuCond aiocb_completion;
 
 struct qemu_paiocb {
     BlockDriverAIOCB common;
@@ -351,10 +354,14 @@ static void *aio_thread(void *unused)
         }
 
         mutex_lock(&lock);
-        aiocb->ret = ret;
         idle_threads++;
         mutex_unlock(&lock);
 
+        qemu_mutex_lock(&aiocb_mutex);
+        aiocb->ret = ret;
+        qemu_cond_broadcast(&aiocb_completion);
+        qemu_mutex_unlock(&aiocb_mutex);
+
         if (kill(pid, aiocb->ev_signo)) die("kill failed");
     }
 
@@ -383,8 +390,11 @@ static void spawn_thread(void)
 
 static void qemu_paio_submit(struct qemu_paiocb *aiocb)
 {
+    qemu_mutex_lock(&aiocb_mutex);
     aiocb->ret = -EINPROGRESS;
     aiocb->active = 0;
+    qemu_mutex_unlock(&aiocb_mutex);
+
     mutex_lock(&lock);
     if (idle_threads == 0 && cur_threads < max_threads)
         spawn_thread();
@@ -397,9 +407,9 @@ static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)
 {
     ssize_t ret;
 
-    mutex_lock(&lock);
+    qemu_mutex_lock(&aiocb_mutex);
     ret = aiocb->ret;
-    mutex_unlock(&lock);
+    qemu_mutex_unlock(&aiocb_mutex);
 
     return ret;
 }
@@ -536,22 +546,26 @@ static void paio_cancel(BlockDriverAIOCB *blockacb)
     struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;
     int active = 0;
 
-    mutex_lock(&lock);
+    qemu_mutex_lock(&aiocb_mutex);
     if (!acb->active) {
         QTAILQ_REMOVE(&request_list, acb, node);
         acb->ret = -ECANCELED;
     } else if (acb->ret == -EINPROGRESS) {
         active = 1;
     }
-    mutex_unlock(&lock);
 
-    if (active) {
-        /* fail safe: if the aio could not be canceled, we wait for
-           it */
-        while (qemu_paio_error(acb) == EINPROGRESS)
-            ;
+    if (!active) {
+        acb->ret = -ECANCELED;
+    } else {
+        while (acb->ret == -EINPROGRESS) {
+            /*
+             * fail safe: if the aio could not be canceled,
+             * we wait for it
+             */
+            qemu_cond_wait(&aiocb_completion, &aiocb_mutex);
+        }
     }
-
+    qemu_mutex_unlock(&aiocb_mutex);
     paio_remove(acb);
 }
 
@@ -623,6 +637,9 @@ int paio_init(void)
     if (posix_aio_state)
         return 0;
 
+    qemu_mutex_init(&aiocb_mutex);
+    qemu_cond_init(&aiocb_completion);
+
     s = qemu_malloc(sizeof(PosixAioState));
 
     sigfillset(&act.sa_mask);

[Qemu-devel] [PATCH 02/12] Introduce work concept in posix-aio-compat.c

[Arun R Bharadwaj]

This patch introduces work concept by introducing the
ThreadletWork structure.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 posix-aio-compat.c |   20 ++++++++++++++------
 1 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 82862ec..ddf42f5 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -33,6 +33,10 @@
 
 static QemuMutex aiocb_mutex;
 static QemuCond aiocb_completion;
+typedef struct ThreadletWork
+{
+    QTAILQ_ENTRY(ThreadletWork) node;
+} ThreadletWork;
 
 struct qemu_paiocb {
     BlockDriverAIOCB common;
@@ -47,13 +51,13 @@ struct qemu_paiocb {
     int ev_signo;
     off_t aio_offset;
 
-    QTAILQ_ENTRY(qemu_paiocb) node;
     int aio_type;
     ssize_t ret;
     int active;
     struct qemu_paiocb *next;
 
     int async_context_id;
+    ThreadletWork work;
 };
 
 typedef struct PosixAioState {
@@ -69,7 +73,7 @@ static pthread_attr_t attr;
 static int max_threads = 64;
 static int cur_threads = 0;
 static int idle_threads = 0;
-static QTAILQ_HEAD(, qemu_paiocb) request_list;
+static QTAILQ_HEAD(, ThreadletWork) request_list;
 
 #ifdef CONFIG_PREADV
 static int preadv_present = 1;
@@ -307,6 +311,7 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
 static void *aio_thread(void *unused)
 {
     pid_t pid;
+    ThreadletWork *work;
 
     pid = getpid();
 
@@ -330,8 +335,11 @@ static void *aio_thread(void *unused)
         if (QTAILQ_EMPTY(&request_list))
             break;
 
-        aiocb = QTAILQ_FIRST(&request_list);
-        QTAILQ_REMOVE(&request_list, aiocb, node);
+        work = QTAILQ_FIRST(&request_list);
+        QTAILQ_REMOVE(&request_list, work, node);
+
+        aiocb = container_of(work, struct qemu_paiocb, work);
+
         aiocb->active = 1;
         idle_threads--;
         mutex_unlock(&lock);
@@ -398,7 +406,7 @@ static void qemu_paio_submit(struct qemu_paiocb *aiocb)
     mutex_lock(&lock);
     if (idle_threads == 0 && cur_threads < max_threads)
         spawn_thread();
-    QTAILQ_INSERT_TAIL(&request_list, aiocb, node);
+    QTAILQ_INSERT_TAIL(&request_list, &aiocb->work, node);
     mutex_unlock(&lock);
     cond_signal(&cond);
 }
@@ -548,7 +556,7 @@ static void paio_cancel(BlockDriverAIOCB *blockacb)
 
     qemu_mutex_lock(&aiocb_mutex);
     if (!acb->active) {
-        QTAILQ_REMOVE(&request_list, acb, node);
+        QTAILQ_REMOVE(&request_list, &acb->work, node);
         acb->ret = -ECANCELED;
     } else if (acb->ret == -EINPROGRESS) {
         active = 1;

[Qemu-devel] [PATCH 03/12] Add callback function to ThreadletWork structure.

[Arun R Bharadwaj]

This patch adds the callback function to the ThreadletWork
structure and moves aio handler as a callback function.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 posix-aio-compat.c |   89 +++++++++++++++++++++++++++++-----------------------
 1 files changed, 50 insertions(+), 39 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index ddf42f5..2792201 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -36,6 +36,7 @@ static QemuCond aiocb_completion;
 typedef struct ThreadletWork
 {
     QTAILQ_ENTRY(ThreadletWork) node;
+    void (*func)(struct ThreadletWork *work);
 } ThreadletWork;
 
 struct qemu_paiocb {
@@ -308,18 +309,14 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
     return nbytes;
 }
 
-static void *aio_thread(void *unused)
+static void *threadlet_worker(void *data)
 {
-    pid_t pid;
-    ThreadletWork *work;
-
-    pid = getpid();
 
     while (1) {
-        struct qemu_paiocb *aiocb;
         ssize_t ret = 0;
         qemu_timeval tv;
         struct timespec ts;
+        ThreadletWork *work;
 
         qemu_gettimeofday(&tv);
         ts.tv_sec = tv.tv_sec + 10;
@@ -332,52 +329,64 @@ static void *aio_thread(void *unused)
             ret = cond_timedwait(&cond, &lock, &ts);
         }
 
-        if (QTAILQ_EMPTY(&request_list))
+        if (QTAILQ_EMPTY(&request_list)) {
+            idle_threads--;
+            cur_threads--;
+            mutex_unlock(&lock);
             break;
-
+        }
         work = QTAILQ_FIRST(&request_list);
         QTAILQ_REMOVE(&request_list, work, node);
-
-        aiocb = container_of(work, struct qemu_paiocb, work);
-
-        aiocb->active = 1;
         idle_threads--;
         mutex_unlock(&lock);
 
-        switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
-        case QEMU_AIO_READ:
-        case QEMU_AIO_WRITE:
-            ret = handle_aiocb_rw(aiocb);
-            break;
-        case QEMU_AIO_FLUSH:
-            ret = handle_aiocb_flush(aiocb);
-            break;
-        case QEMU_AIO_IOCTL:
-            ret = handle_aiocb_ioctl(aiocb);
-            break;
-        default:
-            fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
-            ret = -EINVAL;
-            break;
-        }
-
+        work->func(work);
         mutex_lock(&lock);
         idle_threads++;
         mutex_unlock(&lock);
 
-        qemu_mutex_lock(&aiocb_mutex);
-        aiocb->ret = ret;
-        qemu_cond_broadcast(&aiocb_completion);
-        qemu_mutex_unlock(&aiocb_mutex);
+    }
+
+    return NULL;
+}
+
+static void handle_work(ThreadletWork *work)
+{
+    pid_t pid;
+    ssize_t ret = 0;
+    struct qemu_paiocb *aiocb;
 
-        if (kill(pid, aiocb->ev_signo)) die("kill failed");
+    pid = getpid();
+    aiocb = container_of(work, struct qemu_paiocb, work);
+    qemu_mutex_lock(&aiocb_mutex);
+    aiocb->active = 1;
+    qemu_mutex_unlock(&aiocb_mutex);
+
+    switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
+    case QEMU_AIO_READ:
+    case QEMU_AIO_WRITE:
+        ret = handle_aiocb_rw(aiocb);
+        break;
+    case QEMU_AIO_FLUSH:
+        ret = handle_aiocb_flush(aiocb);
+        break;
+    case QEMU_AIO_IOCTL:
+        ret = handle_aiocb_ioctl(aiocb);
+        break;
+    default:
+        fprintf(stderr, "invalid aio request (0x%x)\n", aiocb->aio_type);
+        ret = -EINVAL;
+        break;
     }
 
-    idle_threads--;
-    cur_threads--;
-    mutex_unlock(&lock);
+    qemu_mutex_lock(&aiocb_mutex);
+    aiocb->ret = ret;
+    qemu_cond_broadcast(&aiocb_completion);
+    qemu_mutex_unlock(&aiocb_mutex);
 
-    return NULL;
+    if (kill(pid, aiocb->ev_signo)) {
+        die("kill failed");
+    }
 }
 
 static void spawn_thread(void)
@@ -391,7 +400,7 @@ static void spawn_thread(void)
     if (sigfillset(&set)) die("sigfillset");
     if (sigprocmask(SIG_SETMASK, &set, &oldset)) die("sigprocmask");
 
-    thread_create(&thread_id, &attr, aio_thread, NULL);
+    thread_create(&thread_id, &attr, threadlet_worker, NULL);
 
     if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
 }
@@ -406,6 +415,8 @@ static void qemu_paio_submit(struct qemu_paiocb *aiocb)
     mutex_lock(&lock);
     if (idle_threads == 0 && cur_threads < max_threads)
         spawn_thread();
+
+    aiocb->work.func = handle_work;
     QTAILQ_INSERT_TAIL(&request_list, &aiocb->work, node);
     mutex_unlock(&lock);
     cond_signal(&cond);

[Qemu-devel] [PATCH 04/12] Add ThreadletQueue.

[Arun R Bharadwaj]

This patch adds a global queue of type ThreadletQueue and
removes the earlier usage of request_list queue.

We want to create the thread on the first submit. Hence we
need to track whether the globalqueue is initialized or not.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 posix-aio-compat.c |  149 +++++++++++++++++++++++++++-------------------------
 1 files changed, 76 insertions(+), 73 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 2792201..011633f 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -31,8 +31,23 @@
 
 #include "block/raw-posix-aio.h"
 
+#define MAX_GLOBAL_THREADS  64
+#define MIN_GLOBAL_THREADS   8
+
 static QemuMutex aiocb_mutex;
 static QemuCond aiocb_completion;
+
+typedef struct ThreadletQueue
+{
+    QemuMutex lock;
+    QemuCond cond;
+    int max_threads;
+    int min_threads;
+    int cur_threads;
+    int idle_threads;
+    QTAILQ_HEAD(, ThreadletWork) request_list;
+} ThreadletQueue;
+
 typedef struct ThreadletWork
 {
     QTAILQ_ENTRY(ThreadletWork) node;
@@ -66,15 +81,10 @@ typedef struct PosixAioState {
     struct qemu_paiocb *first_aio;
 } PosixAioState;
 
-
-static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
-static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
-static pthread_t thread_id;
+/* Default ThreadletQueue */
+static ThreadletQueue globalqueue;
+static int globalqueue_init;
 static pthread_attr_t attr;
-static int max_threads = 64;
-static int cur_threads = 0;
-static int idle_threads = 0;
-static QTAILQ_HEAD(, ThreadletWork) request_list;
 
 #ifdef CONFIG_PREADV
 static int preadv_present = 1;
@@ -93,32 +103,6 @@ static void die(const char *what)
     die2(errno, what);
 }
 
-static void mutex_lock(pthread_mutex_t *mutex)
-{
-    int ret = pthread_mutex_lock(mutex);
-    if (ret) die2(ret, "pthread_mutex_lock");
-}
-
-static void mutex_unlock(pthread_mutex_t *mutex)
-{
-    int ret = pthread_mutex_unlock(mutex);
-    if (ret) die2(ret, "pthread_mutex_unlock");
-}
-
-static int cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
-                           struct timespec *ts)
-{
-    int ret = pthread_cond_timedwait(cond, mutex, ts);
-    if (ret && ret != ETIMEDOUT) die2(ret, "pthread_cond_timedwait");
-    return ret;
-}
-
-static void cond_signal(pthread_cond_t *cond)
-{
-    int ret = pthread_cond_signal(cond);
-    if (ret) die2(ret, "pthread_cond_signal");
-}
-
 static void thread_create(pthread_t *thread, pthread_attr_t *attr,
                           void *(*start_routine)(void*), void *arg)
 {
@@ -311,42 +295,45 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
 
 static void *threadlet_worker(void *data)
 {
+    ThreadletQueue *queue = data;
 
+    qemu_mutex_lock(&queue->lock);
     while (1) {
-        ssize_t ret = 0;
-        qemu_timeval tv;
-        struct timespec ts;
         ThreadletWork *work;
+        int ret = 0;
 
-        qemu_gettimeofday(&tv);
-        ts.tv_sec = tv.tv_sec + 10;
-        ts.tv_nsec = 0;
-
-        mutex_lock(&lock);
-
-        while (QTAILQ_EMPTY(&request_list) &&
-               !(ret == ETIMEDOUT)) {
-            ret = cond_timedwait(&cond, &lock, &ts);
+        while (QTAILQ_EMPTY(&queue->request_list) &&
+               (ret != ETIMEDOUT)) {
+            /* wait for cond to be signalled or broadcast for 1000s */
+            ret = qemu_cond_timedwait((&queue->cond),
+                                      &(queue->lock), 10*100000);
         }
 
-        if (QTAILQ_EMPTY(&request_list)) {
-            idle_threads--;
-            cur_threads--;
-            mutex_unlock(&lock);
-            break;
-        }
-        work = QTAILQ_FIRST(&request_list);
-        QTAILQ_REMOVE(&request_list, work, node);
-        idle_threads--;
-        mutex_unlock(&lock);
+        assert(queue->idle_threads != 0);
+        if (QTAILQ_EMPTY(&queue->request_list)) {
+            if (queue->cur_threads > queue->min_threads) {
+                /* We retain the minimum number of threads */
+                break;
+            }
+        } else {
+            work = QTAILQ_FIRST(&queue->request_list);
+            QTAILQ_REMOVE(&queue->request_list, work, node);
+
+            queue->idle_threads--;
+            qemu_mutex_unlock(&queue->lock);
 
-        work->func(work);
-        mutex_lock(&lock);
-        idle_threads++;
-        mutex_unlock(&lock);
+            /* execute the work function */
+            work->func(work);
 
+            qemu_mutex_lock(&queue->lock);
+            queue->idle_threads++;
+        }
     }
 
+    queue->idle_threads--;
+    queue->cur_threads--;
+    qemu_mutex_unlock(&queue->lock);
+
     return NULL;
 }
 
@@ -389,18 +376,19 @@ static void handle_work(ThreadletWork *work)
     }
 }
 
-static void spawn_thread(void)
+static void spawn_threadlet(ThreadletQueue *queue)
 {
+    pthread_t thread_id;
     sigset_t set, oldset;
 
-    cur_threads++;
-    idle_threads++;
+    queue->cur_threads++;
+    queue->idle_threads++;
 
     /* block all signals */
     if (sigfillset(&set)) die("sigfillset");
     if (sigprocmask(SIG_SETMASK, &set, &oldset)) die("sigprocmask");
 
-    thread_create(&thread_id, &attr, threadlet_worker, NULL);
+    thread_create(&thread_id, &attr, threadlet_worker, queue);
 
     if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
 }
@@ -412,14 +400,29 @@ static void qemu_paio_submit(struct qemu_paiocb *aiocb)
     aiocb->active = 0;
     qemu_mutex_unlock(&aiocb_mutex);
 
-    mutex_lock(&lock);
-    if (idle_threads == 0 && cur_threads < max_threads)
-        spawn_thread();
+    qemu_mutex_lock(&globalqueue.lock);
+
+    if (!globalqueue_init) {
+        globalqueue.cur_threads  = 0;
+        globalqueue.idle_threads = 0;
+        globalqueue.max_threads = MAX_GLOBAL_THREADS;
+        globalqueue.min_threads = MIN_GLOBAL_THREADS;
+        QTAILQ_INIT(&globalqueue.request_list);
+        qemu_mutex_init(&globalqueue.lock);
+        qemu_cond_init(&globalqueue.cond);
+
+        globalqueue_init = 1;
+    }
+
+    if (globalqueue.idle_threads == 0 &&
+        globalqueue.cur_threads < globalqueue.max_threads)
+        spawn_threadlet(&globalqueue);
 
     aiocb->work.func = handle_work;
-    QTAILQ_INSERT_TAIL(&request_list, &aiocb->work, node);
-    mutex_unlock(&lock);
-    cond_signal(&cond);
+
+    QTAILQ_INSERT_TAIL(&globalqueue.request_list, &aiocb->work, node);
+    qemu_cond_signal(&globalqueue.cond);
+    qemu_mutex_unlock(&globalqueue.lock);
 }
 
 static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)
@@ -566,12 +569,14 @@ static void paio_cancel(BlockDriverAIOCB *blockacb)
     int active = 0;
 
     qemu_mutex_lock(&aiocb_mutex);
+    qemu_mutex_lock(&globalqueue.lock);
     if (!acb->active) {
-        QTAILQ_REMOVE(&request_list, &acb->work, node);
+        QTAILQ_REMOVE(&globalqueue.request_list, &acb->work, node);
         acb->ret = -ECANCELED;
     } else if (acb->ret == -EINPROGRESS) {
         active = 1;
     }
+    qemu_mutex_unlock(&globalqueue.lock);
 
     if (!active) {
         acb->ret = -ECANCELED;
@@ -689,8 +694,6 @@ int paio_init(void)
     if (ret)
         die2(ret, "pthread_attr_setdetachstate");
 
-    QTAILQ_INIT(&request_list);
-
     posix_aio_state = s;
     return 0;
 }

[Qemu-devel] [PATCH 05/12] Threadlet: Add submit_work threadlet API.

[Arun R Bharadwaj]

This patch adds submit work threadlet API and shows how
the qemu_paio_submit changes to submit_work.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 posix-aio-compat.c |   33 ++++++++++++++++++++++-----------
 1 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 011633f..62e32e3 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -393,13 +393,13 @@ static void spawn_threadlet(ThreadletQueue *queue)
     if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
 }
 
-static void qemu_paio_submit(struct qemu_paiocb *aiocb)
+/**
+ * submit_work: Submit to the global queue a new task to be executed
+ *                   asynchronously.
+ * @work: Contains information about the task that needs to be submitted.
+ */
+static void submit_work(ThreadletWork *work)
 {
-    qemu_mutex_lock(&aiocb_mutex);
-    aiocb->ret = -EINPROGRESS;
-    aiocb->active = 0;
-    qemu_mutex_unlock(&aiocb_mutex);
-
     qemu_mutex_lock(&globalqueue.lock);
 
     if (!globalqueue_init) {
@@ -415,13 +415,13 @@ static void qemu_paio_submit(struct qemu_paiocb *aiocb)
     }
 
     if (globalqueue.idle_threads == 0 &&
-        globalqueue.cur_threads < globalqueue.max_threads)
+        globalqueue.cur_threads < globalqueue.max_threads) {
         spawn_threadlet(&globalqueue);
 
-    aiocb->work.func = handle_work;
-
-    QTAILQ_INSERT_TAIL(&globalqueue.request_list, &aiocb->work, node);
-    qemu_cond_signal(&globalqueue.cond);
+    } else {
+        qemu_cond_signal(&globalqueue.cond);
+    }
+    QTAILQ_INSERT_TAIL(&globalqueue.request_list, work, node);
     qemu_mutex_unlock(&globalqueue.lock);
 }
 
@@ -448,6 +448,17 @@ static int qemu_paio_error(struct qemu_paiocb *aiocb)
     return ret;
 }
 
+static void qemu_paio_submit(struct qemu_paiocb *aiocb)
+{
+    qemu_mutex_lock(&aiocb_mutex);
+    aiocb->ret = -EINPROGRESS;
+    aiocb->active = 0;
+    qemu_mutex_unlock(&aiocb_mutex);
+
+    aiocb->work.func = handle_work;
+    submit_work(&aiocb->work);
+}
+
 static int posix_aio_process_queue(void *opaque)
 {
     PosixAioState *s = opaque;

[Qemu-devel] [PATCH 06/12] Threadlet: Add dequeue_work threadlet API and remove active field.

[Arun R Bharadwaj]

This patch adds dequeue_work threadlet API and shows how
the paio_cancel changes to dequeue_work.

The active field in the qemu_aiocb structure is now useless.
Remove it.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 posix-aio-compat.c |   48 ++++++++++++++++++++++++++----------------------
 1 files changed, 26 insertions(+), 22 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 62e32e3..95ba805 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -69,7 +69,6 @@ struct qemu_paiocb {
 
     int aio_type;
     ssize_t ret;
-    int active;
     struct qemu_paiocb *next;
 
     int async_context_id;
@@ -345,9 +344,6 @@ static void handle_work(ThreadletWork *work)
 
     pid = getpid();
     aiocb = container_of(work, struct qemu_paiocb, work);
-    qemu_mutex_lock(&aiocb_mutex);
-    aiocb->active = 1;
-    qemu_mutex_unlock(&aiocb_mutex);
 
     switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
     case QEMU_AIO_READ:
@@ -452,7 +448,6 @@ static void qemu_paio_submit(struct qemu_paiocb *aiocb)
 {
     qemu_mutex_lock(&aiocb_mutex);
     aiocb->ret = -EINPROGRESS;
-    aiocb->active = 0;
     qemu_mutex_unlock(&aiocb_mutex);
 
     aiocb->work.func = handle_work;
@@ -574,33 +569,42 @@ static void paio_remove(struct qemu_paiocb *acb)
     }
 }
 
-static void paio_cancel(BlockDriverAIOCB *blockacb)
+/**
+ * dequeue_work: Cancel a task queued on the global queue.
+ * @work: Contains the information of the task that needs to be cancelled.
+ *
+ * Returns:	0 if successfully dequeued work.
+ *		1 otherwise.
+ */
+static int dequeue_work(ThreadletWork *work)
 {
-    struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;
-    int active = 0;
+    int ret = 1;
+    ThreadletWork *ret_work;
 
-    qemu_mutex_lock(&aiocb_mutex);
     qemu_mutex_lock(&globalqueue.lock);
-    if (!acb->active) {
-        QTAILQ_REMOVE(&globalqueue.request_list, &acb->work, node);
-        acb->ret = -ECANCELED;
-    } else if (acb->ret == -EINPROGRESS) {
-        active = 1;
+    QTAILQ_FOREACH(ret_work, &(globalqueue.request_list), node) {
+        if (ret_work == work) {
+            QTAILQ_REMOVE(&globalqueue.request_list, ret_work, node);
+            ret = 0;
+            break;
+        }
     }
     qemu_mutex_unlock(&globalqueue.lock);
 
-    if (!active) {
-        acb->ret = -ECANCELED;
-    } else {
+    return ret;
+}
+
+static void paio_cancel(BlockDriverAIOCB *blockacb)
+{
+    struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;
+    if (dequeue_work(&acb->work) != 0) {
+        /* Wait for running work item to complete */
+        qemu_mutex_lock(&aiocb_mutex);
         while (acb->ret == -EINPROGRESS) {
-            /*
-             * fail safe: if the aio could not be canceled,
-             * we wait for it
-             */
             qemu_cond_wait(&aiocb_completion, &aiocb_mutex);
         }
+        qemu_mutex_unlock(&aiocb_mutex);
     }
-    qemu_mutex_unlock(&aiocb_mutex);
     paio_remove(acb);
 }
 

[Qemu-devel] [PATCH 07/12] Remove thread_create routine.

[Arun R Bharadwaj]

Remove thread_create and use qemu_thread_create instead.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 posix-aio-compat.c |   29 ++---------------------------
 1 files changed, 2 insertions(+), 27 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 95ba805..a7625d8 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -13,7 +13,6 @@
 
 #include <sys/ioctl.h>
 #include <sys/types.h>
-#include <pthread.h>
 #include <unistd.h>
 #include <errno.h>
 #include <time.h>
@@ -83,7 +82,6 @@ typedef struct PosixAioState {
 /* Default ThreadletQueue */
 static ThreadletQueue globalqueue;
 static int globalqueue_init;
-static pthread_attr_t attr;
 
 #ifdef CONFIG_PREADV
 static int preadv_present = 1;
@@ -102,13 +100,6 @@ static void die(const char *what)
     die2(errno, what);
 }
 
-static void thread_create(pthread_t *thread, pthread_attr_t *attr,
-                          void *(*start_routine)(void*), void *arg)
-{
-    int ret = pthread_create(thread, attr, start_routine, arg);
-    if (ret) die2(ret, "pthread_create");
-}
-
 static ssize_t handle_aiocb_ioctl(struct qemu_paiocb *aiocb)
 {
     int ret;
@@ -374,19 +365,12 @@ static void handle_work(ThreadletWork *work)
 
 static void spawn_threadlet(ThreadletQueue *queue)
 {
-    pthread_t thread_id;
-    sigset_t set, oldset;
+    QemuThread thread;
 
     queue->cur_threads++;
     queue->idle_threads++;
 
-    /* block all signals */
-    if (sigfillset(&set)) die("sigfillset");
-    if (sigprocmask(SIG_SETMASK, &set, &oldset)) die("sigprocmask");
-
-    thread_create(&thread_id, &attr, threadlet_worker, queue);
-
-    if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
+    qemu_thread_create(&thread, threadlet_worker, queue);
 }
 
 /**
@@ -671,7 +655,6 @@ int paio_init(void)
     struct sigaction act;
     PosixAioState *s;
     int fds[2];
-    int ret;
 
     if (posix_aio_state)
         return 0;
@@ -701,14 +684,6 @@ int paio_init(void)
     qemu_aio_set_fd_handler(s->rfd, posix_aio_read, NULL, posix_aio_flush,
         posix_aio_process_queue, s);
 
-    ret = pthread_attr_init(&attr);
-    if (ret)
-        die2(ret, "pthread_attr_init");
-
-    ret = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
-    if (ret)
-        die2(ret, "pthread_attr_setdetachstate");
-
     posix_aio_state = s;
     return 0;
 }

[Qemu-devel] [PATCH 08/12] Threadlet: Add aio_signal_handler threadlet API

[Arun R Bharadwaj]

This patch adds aio_signal_handler threadlet API. Earler
posix-aio-compat.c had its own signal handler code. Now
abstract this, in the later patch it is moved to a generic
code so that it can be used by other subsystems.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 Makefile.objs      |    1 +
 posix-aio-compat.c |   30 ++++++++----------------------
 qemu-threadlet.c   |   39 +++++++++++++++++++++++++++++++++++++++
 qemu-threadlet.h   |   19 +++++++++++++++++++
 vl.c               |    3 +++
 5 files changed, 70 insertions(+), 22 deletions(-)
 create mode 100644 qemu-threadlet.c
 create mode 100644 qemu-threadlet.h

diff --git a/Makefile.objs b/Makefile.objs
index 3b7ec27..3b11dd0 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -10,6 +10,7 @@ qobject-obj-y += qerror.o
 block-obj-y = cutils.o cache-utils.o qemu-malloc.o qemu-option.o module.o
 block-obj-y += nbd.o block.o aio.o aes.o osdep.o qemu-config.o
 block-obj-$(CONFIG_POSIX) += qemu-thread.o
+block-obj-$(CONFIG_POSIX) += qemu-threadlet.o
 block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
 block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
 
diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index a7625d8..96e28db 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -327,11 +327,14 @@ static void *threadlet_worker(void *data)
     return NULL;
 }
 
+static PosixAioState *posix_aio_state;
+
 static void handle_work(ThreadletWork *work)
 {
     pid_t pid;
     ssize_t ret = 0;
     struct qemu_paiocb *aiocb;
+    char byte = 0;
 
     pid = getpid();
     aiocb = container_of(work, struct qemu_paiocb, work);
@@ -358,6 +361,11 @@ static void handle_work(ThreadletWork *work)
     qemu_cond_broadcast(&aiocb_completion);
     qemu_mutex_unlock(&aiocb_mutex);
 
+    ret = write(posix_aio_state->wfd, &byte, sizeof(byte));
+    if (ret < 0 && errno != EAGAIN) {
+        die("write()");
+    }
+
     if (kill(pid, aiocb->ev_signo)) {
         die("kill failed");
     }
@@ -518,22 +526,6 @@ static int posix_aio_flush(void *opaque)
     return !!s->first_aio;
 }
 
-static PosixAioState *posix_aio_state;
-
-static void aio_signal_handler(int signum)
-{
-    if (posix_aio_state) {
-        char byte = 0;
-        ssize_t ret;
-
-        ret = write(posix_aio_state->wfd, &byte, sizeof(byte));
-        if (ret < 0 && errno != EAGAIN)
-            die("write()");
-    }
-
-    qemu_service_io();
-}
-
 static void paio_remove(struct qemu_paiocb *acb)
 {
     struct qemu_paiocb **pacb;
@@ -652,7 +644,6 @@ BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,
 
 int paio_init(void)
 {
-    struct sigaction act;
     PosixAioState *s;
     int fds[2];
 
@@ -664,11 +655,6 @@ int paio_init(void)
 
     s = qemu_malloc(sizeof(PosixAioState));
 
-    sigfillset(&act.sa_mask);
-    act.sa_flags = 0; /* do not restart syscalls to interrupt select() */
-    act.sa_handler = aio_signal_handler;
-    sigaction(SIGUSR2, &act, NULL);
-
     s->first_aio = NULL;
     if (qemu_pipe(fds) == -1) {
         fprintf(stderr, "failed to create pipe\n");
diff --git a/qemu-threadlet.c b/qemu-threadlet.c
new file mode 100644
index 0000000..857d08d
--- /dev/null
+++ b/qemu-threadlet.c
@@ -0,0 +1,39 @@
+/*
+ * Threadlet support for offloading tasks to be executed asynchronously
+ *
+ * Copyright IBM, Corp. 2008
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Anthony Liguori     <aliguori@us.ibm.com>
+ *  Aneesh Kumar K.V    <aneesh.kumar@linux.vnet.ibm.com>
+ *  Gautham R Shenoy    <gautham.shenoy@gmail.com>
+ *  Arun R Bharadwaj    <arun@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#include <signal.h>
+
+#include "qemu-threadlet.h"
+#include "osdep.h"
+
+static void threadlet_io_completion_signal_handler(int signum)
+{
+    qemu_service_io();
+}
+
+static void threadlet_register_signal_handler(void)
+{
+    struct sigaction act;
+    sigfillset(&act.sa_mask);
+    act.sa_flags = 0; /* do not restart syscalls to interrupt select() */
+    act.sa_handler = threadlet_io_completion_signal_handler;
+    sigaction(SIGUSR2, &act, NULL);
+}
+
+void threadlet_init(void)
+{
+    threadlet_register_signal_handler();
+}
diff --git a/qemu-threadlet.h b/qemu-threadlet.h
new file mode 100644
index 0000000..2c225d6
--- /dev/null
+++ b/qemu-threadlet.h
@@ -0,0 +1,19 @@
+/*
+ * Threadlet support for offloading tasks to be executed asynchronously
+ *
+ * Copyright IBM, Corp. 2008
+ * Copyright IBM, Corp. 2010
+ *
+ * Authors:
+ *  Anthony Liguori     <aliguori@us.ibm.com>
+ *  Aneesh Kumar K.V    <aneesh.kumar@linux.vnet.ibm.com>
+ *  Gautham R Shenoy    <gautham.shenoy@gmail.com>
+ *  Arun R Bharadwaj    <arun@linux.vnet.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#include "qemu-common.h"
+
+void threadlet_init(void);
diff --git a/vl.c b/vl.c
index df414ef..d04fc7a 100644
--- a/vl.c
+++ b/vl.c
@@ -148,6 +148,7 @@ int main(int argc, char **argv)
 #include "qemu-config.h"
 #include "qemu-objects.h"
 #include "qemu-options.h"
+#include "qemu-threadlet.h"
 #ifdef CONFIG_VIRTFS
 #include "fsdev/qemu-fsdev.h"
 #endif
@@ -2922,6 +2923,8 @@ int main(int argc, char **argv, char **envp)
             exit(1);
     }
 
+    threadlet_init();
+
     /* init generic devices */
     if (qemu_opts_foreach(qemu_find_opts("device"), device_init_func, NULL, 1) != 0)
         exit(1);

[Qemu-devel] [PATCH 09/12] Remove all instances of CONFIG_THREAD

[Arun R Bharadwaj]

Remove all instances of CONFIG_THREAD, which is not used
anymore.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 configure |    2 --
 1 files changed, 0 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index a079a49..addf733 100755
--- a/configure
+++ b/configure
@@ -2456,7 +2456,6 @@ if test "$vnc_png" != "no" ; then
 fi
 if test "$vnc_thread" != "no" ; then
   echo "CONFIG_VNC_THREAD=y" >> $config_host_mak
-  echo "CONFIG_THREAD=y" >> $config_host_mak
 fi
 if test "$fnmatch" = "yes" ; then
   echo "CONFIG_FNMATCH=y" >> $config_host_mak
@@ -2534,7 +2533,6 @@ if test "$xen" = "yes" ; then
 fi
 if test "$io_thread" = "yes" ; then
   echo "CONFIG_IOTHREAD=y" >> $config_host_mak
-  echo "CONFIG_THREAD=y" >> $config_host_mak
 fi
 if test "$linux_aio" = "yes" ; then
   echo "CONFIG_LINUX_AIO=y" >> $config_host_mak

[Qemu-devel] [PATCH 10/12] Move threadlet code to qemu-threadlets.c

[Arun R Bharadwaj]

This patch moves the threadlet queue API code to
qemu-threadlets.c where these APIs can be used by
other subsystems.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 posix-aio-compat.c |  137 ----------------------------------------------------
 qemu-threadlet.c   |  115 ++++++++++++++++++++++++++++++++++++++++++++
 qemu-threadlet.h   |   25 +++++++++
 3 files changed, 141 insertions(+), 136 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 96e28db..4fc9581 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -26,33 +26,13 @@
 #include "qemu-common.h"
 #include "trace.h"
 #include "block_int.h"
-#include "qemu-thread.h"
+#include "qemu-threadlet.h"
 
 #include "block/raw-posix-aio.h"
 
-#define MAX_GLOBAL_THREADS  64
-#define MIN_GLOBAL_THREADS   8
-
 static QemuMutex aiocb_mutex;
 static QemuCond aiocb_completion;
 
-typedef struct ThreadletQueue
-{
-    QemuMutex lock;
-    QemuCond cond;
-    int max_threads;
-    int min_threads;
-    int cur_threads;
-    int idle_threads;
-    QTAILQ_HEAD(, ThreadletWork) request_list;
-} ThreadletQueue;
-
-typedef struct ThreadletWork
-{
-    QTAILQ_ENTRY(ThreadletWork) node;
-    void (*func)(struct ThreadletWork *work);
-} ThreadletWork;
-
 struct qemu_paiocb {
     BlockDriverAIOCB common;
     int aio_fildes;
@@ -79,10 +59,6 @@ typedef struct PosixAioState {
     struct qemu_paiocb *first_aio;
 } PosixAioState;
 
-/* Default ThreadletQueue */
-static ThreadletQueue globalqueue;
-static int globalqueue_init;
-
 #ifdef CONFIG_PREADV
 static int preadv_present = 1;
 #else
@@ -283,50 +259,6 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
     return nbytes;
 }
 
-static void *threadlet_worker(void *data)
-{
-    ThreadletQueue *queue = data;
-
-    qemu_mutex_lock(&queue->lock);
-    while (1) {
-        ThreadletWork *work;
-        int ret = 0;
-
-        while (QTAILQ_EMPTY(&queue->request_list) &&
-               (ret != ETIMEDOUT)) {
-            /* wait for cond to be signalled or broadcast for 1000s */
-            ret = qemu_cond_timedwait((&queue->cond),
-                                      &(queue->lock), 10*100000);
-        }
-
-        assert(queue->idle_threads != 0);
-        if (QTAILQ_EMPTY(&queue->request_list)) {
-            if (queue->cur_threads > queue->min_threads) {
-                /* We retain the minimum number of threads */
-                break;
-            }
-        } else {
-            work = QTAILQ_FIRST(&queue->request_list);
-            QTAILQ_REMOVE(&queue->request_list, work, node);
-
-            queue->idle_threads--;
-            qemu_mutex_unlock(&queue->lock);
-
-            /* execute the work function */
-            work->func(work);
-
-            qemu_mutex_lock(&queue->lock);
-            queue->idle_threads++;
-        }
-    }
-
-    queue->idle_threads--;
-    queue->cur_threads--;
-    qemu_mutex_unlock(&queue->lock);
-
-    return NULL;
-}
-
 static PosixAioState *posix_aio_state;
 
 static void handle_work(ThreadletWork *work)
@@ -371,48 +303,6 @@ static void handle_work(ThreadletWork *work)
     }
 }
 
-static void spawn_threadlet(ThreadletQueue *queue)
-{
-    QemuThread thread;
-
-    queue->cur_threads++;
-    queue->idle_threads++;
-
-    qemu_thread_create(&thread, threadlet_worker, queue);
-}
-
-/**
- * submit_work: Submit to the global queue a new task to be executed
- *                   asynchronously.
- * @work: Contains information about the task that needs to be submitted.
- */
-static void submit_work(ThreadletWork *work)
-{
-    qemu_mutex_lock(&globalqueue.lock);
-
-    if (!globalqueue_init) {
-        globalqueue.cur_threads  = 0;
-        globalqueue.idle_threads = 0;
-        globalqueue.max_threads = MAX_GLOBAL_THREADS;
-        globalqueue.min_threads = MIN_GLOBAL_THREADS;
-        QTAILQ_INIT(&globalqueue.request_list);
-        qemu_mutex_init(&globalqueue.lock);
-        qemu_cond_init(&globalqueue.cond);
-
-        globalqueue_init = 1;
-    }
-
-    if (globalqueue.idle_threads == 0 &&
-        globalqueue.cur_threads < globalqueue.max_threads) {
-        spawn_threadlet(&globalqueue);
-
-    } else {
-        qemu_cond_signal(&globalqueue.cond);
-    }
-    QTAILQ_INSERT_TAIL(&globalqueue.request_list, work, node);
-    qemu_mutex_unlock(&globalqueue.lock);
-}
-
 static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)
 {
     ssize_t ret;
@@ -545,31 +435,6 @@ static void paio_remove(struct qemu_paiocb *acb)
     }
 }
 
-/**
- * dequeue_work: Cancel a task queued on the global queue.
- * @work: Contains the information of the task that needs to be cancelled.
- *
- * Returns:	0 if successfully dequeued work.
- *		1 otherwise.
- */
-static int dequeue_work(ThreadletWork *work)
-{
-    int ret = 1;
-    ThreadletWork *ret_work;
-
-    qemu_mutex_lock(&globalqueue.lock);
-    QTAILQ_FOREACH(ret_work, &(globalqueue.request_list), node) {
-        if (ret_work == work) {
-            QTAILQ_REMOVE(&globalqueue.request_list, ret_work, node);
-            ret = 0;
-            break;
-        }
-    }
-    qemu_mutex_unlock(&globalqueue.lock);
-
-    return ret;
-}
-
 static void paio_cancel(BlockDriverAIOCB *blockacb)
 {
     struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;
diff --git a/qemu-threadlet.c b/qemu-threadlet.c
index 857d08d..6523f08 100644
--- a/qemu-threadlet.c
+++ b/qemu-threadlet.c
@@ -19,6 +19,12 @@
 #include "qemu-threadlet.h"
 #include "osdep.h"
 
+#define MAX_GLOBAL_THREADS  64
+#define MIN_GLOBAL_THREADS   8
+
+static ThreadletQueue globalqueue;
+static int globalqueue_init;
+
 static void threadlet_io_completion_signal_handler(int signum)
 {
     qemu_service_io();
@@ -37,3 +43,112 @@ void threadlet_init(void)
 {
     threadlet_register_signal_handler();
 }
+
+static void *threadlet_worker(void *data)
+{
+    ThreadletQueue *queue = data;
+
+    qemu_mutex_lock(&queue->lock);
+    while (1) {
+        ThreadletWork *work;
+        int ret = 0;
+
+        while (QTAILQ_EMPTY(&queue->request_list) &&
+               (ret != ETIMEDOUT)) {
+            /* wait for cond to be signalled or broadcast for 1000s */
+            ret = qemu_cond_timedwait((&queue->cond),
+                                         &(queue->lock), 10*100000);
+        }
+
+        assert(queue->idle_threads != 0);
+        if (QTAILQ_EMPTY(&queue->request_list)) {
+            if (queue->cur_threads > queue->min_threads) {
+                /* We retain the minimum number of threads */
+                break;
+            }
+        } else {
+            work = QTAILQ_FIRST(&queue->request_list);
+            QTAILQ_REMOVE(&queue->request_list, work, node);
+
+            queue->idle_threads--;
+            qemu_mutex_unlock(&queue->lock);
+
+            /* execute the work function */
+            work->func(work);
+
+            qemu_mutex_lock(&queue->lock);
+            queue->idle_threads++;
+        }
+    }
+
+    queue->idle_threads--;
+    queue->cur_threads--;
+    qemu_mutex_unlock(&queue->lock);
+
+    return NULL;
+}
+
+static void spawn_threadlet(ThreadletQueue *queue)
+{
+    QemuThread thread;
+
+    queue->cur_threads++;
+    queue->idle_threads++;
+
+    qemu_thread_create(&thread, threadlet_worker, queue);
+}
+
+/**
+ * submit_work: Submit to the global queue a new task to be executed
+ *                   asynchronously.
+ * @work: Contains information about the task that needs to be submitted.
+ */
+void submit_work(ThreadletWork *work)
+{
+    if (!globalqueue_init) {
+        globalqueue.cur_threads  = 0;
+        globalqueue.idle_threads = 0;
+        globalqueue.max_threads = MAX_GLOBAL_THREADS;
+        globalqueue.min_threads = MIN_GLOBAL_THREADS;
+        QTAILQ_INIT(&globalqueue.request_list);
+        qemu_mutex_init(&globalqueue.lock);
+        qemu_cond_init(&globalqueue.cond);
+
+        globalqueue_init = 1;
+    }
+
+    qemu_mutex_lock(&globalqueue.lock);
+    if (globalqueue.idle_threads == 0 &&
+        globalqueue.cur_threads < globalqueue.max_threads) {
+        spawn_threadlet(&globalqueue);
+    } else {
+        qemu_cond_signal(&globalqueue.cond);
+    }
+    QTAILQ_INSERT_TAIL(&globalqueue.request_list, work, node);
+    qemu_mutex_unlock(&globalqueue.lock);
+}
+
+/**
+ * dequeue_work: Cancel a task queued on the global queue.
+ * @work: Contains the information of the task that needs to be cancelled.
+ *
+ * Returns:     0 if successfully dequeued work.
+ *              1 otherwise.
+ */
+int dequeue_work(ThreadletWork *work)
+{
+    int ret = 1;
+    ThreadletWork *ret_work;
+
+    qemu_mutex_lock(&globalqueue.lock);
+    QTAILQ_FOREACH(ret_work, &(globalqueue.request_list), node) {
+        if (ret_work == work) {
+            QTAILQ_REMOVE(&globalqueue.request_list, ret_work, node);
+            ret = 0;
+            break;
+        }
+    }
+    qemu_mutex_unlock(&globalqueue.lock);
+
+    return ret;
+}
diff --git a/qemu-threadlet.h b/qemu-threadlet.h
index 2c225d6..6b11c86 100644
--- a/qemu-threadlet.h
+++ b/qemu-threadlet.h
@@ -14,6 +14,31 @@
  * the COPYING file in the top-level directory.
  */
 
+#ifndef QEMU_ASYNC_WORK_H
+#define QEMU_ASYNC_WORK_H
+
+#include "qemu-queue.h"
 #include "qemu-common.h"
+#include "qemu-thread.h"
+
+typedef struct ThreadletQueue
+{
+    QemuMutex lock;
+    QemuCond cond;
+    int max_threads;
+    int min_threads;
+    int cur_threads;
+    int idle_threads;
+    QTAILQ_HEAD(, ThreadletWork) request_list;
+} ThreadletQueue;
+
+typedef struct ThreadletWork
+{
+    QTAILQ_ENTRY(ThreadletWork) node;
+    void (*func)(struct ThreadletWork *work);
+} ThreadletWork;
 
+void submit_work(ThreadletWork *work);
+int dequeue_work(ThreadletWork *work);
 void threadlet_init(void);
+#endif

[Qemu-devel] [PATCH 11/12] Threadlets: Add functionality to create private queues.

[Arun R Bharadwaj]

This patch allows subsystems to create their own private
queues with associated pools of threads.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 qemu-threadlet.c |   85 +++++++++++++++++++++++++++++++++++++-----------------
 qemu-threadlet.h |    4 +++
 2 files changed, 63 insertions(+), 26 deletions(-)

diff --git a/qemu-threadlet.c b/qemu-threadlet.c
index 6523f08..4bad8c6 100644
--- a/qemu-threadlet.c
+++ b/qemu-threadlet.c
@@ -99,6 +99,25 @@ static void spawn_threadlet(ThreadletQueue *queue)
 }
 
 /**
+ * submit_work_to_queue: Submit a new task to a private queue to be
+ *                            executed asynchronously.
+ * @queue: Per-subsystem private queue to which the new task needs
+ *         to be submitted.
+ * @work: Contains information about the task that needs to be submitted.
+ */
+void submit_work_to_queue(ThreadletQueue *queue, ThreadletWork *work)
+{
+    qemu_mutex_lock(&queue->lock);
+    if (queue->idle_threads == 0 && queue->cur_threads < queue->max_threads) {
+        spawn_threadlet(queue);
+    } else {
+        qemu_cond_signal(&queue->cond);
+    }
+    QTAILQ_INSERT_TAIL(&queue->request_list, work, node);
+    qemu_mutex_unlock(&queue->lock);
+}
+
+/**
  * submit_work: Submit to the global queue a new task to be executed
  *                   asynchronously.
  * @work: Contains information about the task that needs to be submitted.
@@ -106,49 +125,63 @@ static void spawn_threadlet(ThreadletQueue *queue)
 void submit_work(ThreadletWork *work)
 {
     if (!globalqueue_init) {
-        globalqueue.cur_threads  = 0;
-        globalqueue.idle_threads = 0;
-        globalqueue.max_threads = MAX_GLOBAL_THREADS;
-        globalqueue.min_threads = MIN_GLOBAL_THREADS;
-        QTAILQ_INIT(&globalqueue.request_list);
-        qemu_mutex_init(&globalqueue.lock);
-        qemu_cond_init(&globalqueue.cond);
-
+        threadlet_queue_init(&globalqueue, MAX_GLOBAL_THREADS,
+                                MIN_GLOBAL_THREADS);
         globalqueue_init = 1;
     }
 
-    qemu_mutex_lock(&globalqueue.lock);
-    if (globalqueue.idle_threads == 0 &&
-        globalqueue.cur_threads < globalqueue.max_threads) {
-        spawn_threadlet(&globalqueue);
-    } else {
-        qemu_cond_signal(&globalqueue.cond);
-    }
-    QTAILQ_INSERT_TAIL(&globalqueue.request_list, work, node);
-    qemu_mutex_unlock(&globalqueue.lock);
+    submit_work_to_queue(&globalqueue, work);
 }
 
 /**
- * dequeue_work: Cancel a task queued on the global queue.
+ * dequeue_work_on_queue: Cancel a task queued on a Queue.
+ * @queue: The queue containing the task to be cancelled.
  * @work: Contains the information of the task that needs to be cancelled.
- *
- * Returns:     0 if successfully dequeued work.
- *              1 otherwise.
  */
-int dequeue_work(ThreadletWork *work)
+int dequeue_work_on_queue(ThreadletQueue *queue, ThreadletWork *work)
 {
     int ret = 1;
     ThreadletWork *ret_work;
 
-    qemu_mutex_lock(&globalqueue.lock);
-    QTAILQ_FOREACH(ret_work, &(globalqueue.request_list), node) {
+    qemu_mutex_lock(&queue->lock);
+    QTAILQ_FOREACH(ret_work, &(queue->request_list), node) {
         if (ret_work == work) {
-            QTAILQ_REMOVE(&globalqueue.request_list, ret_work, node);
+            QTAILQ_REMOVE(&queue->request_list, work, node);
             ret = 0;
             break;
         }
     }
-    qemu_mutex_unlock(&globalqueue.lock);
+    qemu_mutex_unlock(&queue->lock);
 
     return ret;
 }
+
+/**
+ * dequeue_work: Cancel a task queued on the global queue.
+ * @work: Contains the information of the task that needs to be cancelled.
+ *
+ * Returns:     0 if successfully dequeued work.
+ *              1 otherwise.
+ */
+int dequeue_work(ThreadletWork *work)
+{
+    return dequeue_work_on_queue(&globalqueue, work);
+}
+
+/**
+ * threadlet_queue_init: Initialize a threadlet queue.
+ * @queue: The threadlet queue to be initialized.
+ * @max_threads: Maximum number of threads processing the queue.
+ * @min_threads: Minimum number of threads processing the queue.
+ */
+void threadlet_queue_init(ThreadletQueue *queue,
+                                    int max_threads, int min_threads)
+{
+    queue->cur_threads  = 0;
+    queue->idle_threads = 0;
+    queue->max_threads  = max_threads;
+    queue->min_threads  = min_threads;
+    QTAILQ_INIT(&queue->request_list);
+    qemu_mutex_init(&queue->lock);
+    qemu_cond_init(&queue->cond);
+}
diff --git a/qemu-threadlet.h b/qemu-threadlet.h
index 6b11c86..25e77f2 100644
--- a/qemu-threadlet.h
+++ b/qemu-threadlet.h
@@ -38,7 +38,11 @@ typedef struct ThreadletWork
     void (*func)(struct ThreadletWork *work);
 } ThreadletWork;
 
+void submit_work_to_queue(ThreadletQueue *queue, ThreadletWork *work);
 void submit_work(ThreadletWork *work);
+int dequeue_work_on_queue(ThreadletQueue *queue, ThreadletWork *work);
 int dequeue_work(ThreadletWork *work);
 void threadlet_init(void);
+void threadlet_queue_init(ThreadletQueue *queue, int max_threads,
+                          int min_threads);
 #endif

[Qemu-devel] [PATCH 12/12] Threadlets: Add documentation

[Arun R Bharadwaj]

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Signed-off-by: Gautham R Shenoy <gautham.shenoy@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 docs/async-support.txt |  141 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 141 insertions(+), 0 deletions(-)
 create mode 100644 docs/async-support.txt

diff --git a/docs/async-support.txt b/docs/async-support.txt
new file mode 100644
index 0000000..9f22b9a
--- /dev/null
+++ b/docs/async-support.txt
@@ -0,0 +1,141 @@
+== How to use the threadlets infrastructure supported in Qemu ==
+
+== Threadlets ==
+
+Q.1: What are threadlets ?
+A.1: Threadlets is an infrastructure within QEMU that allows other subsystems
+     to offload possibly blocking work to a queue to be processed by a pool
+     of threads asynchronously.
+
+Q.2: When would one want to use threadlets ?
+A.2: Threadlets are useful when there are operations that can be performed
+     outside the context of the VCPU/IO threads inorder to free these latter
+     to service any other guest requests.
+
+Q.3: I have some work that can be executed in an asynchronous context. How
+     should I go about it ?
+A.3: One could follow the steps listed below:
+
+     - Define a function which would do the asynchronous work.
+	static void my_threadlet_func(ThreadletWork *work)
+	{
+	}
+
+     - Declare an object of type ThreadletWork;
+	ThreadletWork work;
+
+
+     - Assign a value to the "func" member of ThreadletWork object.
+	work.func = my_threadlet_func;
+
+     - Submit the threadlet to the global queue.
+	submit_threadletwork(&work);
+
+     - Continue servicing some other guest operations.
+
+Q.4: I want to my_threadlet_func to access some non-global data. How do I do
+     that ?
+A.4: Suppose you want my_threadlet_func to access some non-global data-object
+     of type myPrivateData. In that case one could follow the following steps.
+
+     - Define a member of the type ThreadletWork within myPrivateData.
+	typedef struct MyPrivateData {
+		...;
+		...;
+		...;
+		ThreadletWork work;
+	} MyPrivateData;
+
+	MyPrivateData my_data;
+
+     - Initialize myData.work as described in A.3
+	myData.work.func = my_threadlet_func;
+	submit_threadletwork(&myData.work);
+
+     - Access the myData object inside my_threadlet_func() using container_of
+       primitive
+	static void my_threadlet_func(ThreadletWork *work)
+	{
+		myPrivateData *mydata_ptr;
+		mydata_ptr = container_of(work, myPrivateData, work);
+
+		/* mydata_ptr now points to myData object */
+	}
+
+Q.5: Are there any precautions one must take while sharing data with the
+     Asynchronous thread-pool ?
+A.5: Yes, make sure that the helper function of the type my_threadlet_func()
+     does not access/modify data when it can be accessed or modified in the
+     context of VCPU thread or IO thread. This is because the asynchronous
+     threads in the pool can run in parallel with the VCPU/IOThreads as shown
+     in the figure.
+
+     A typical workflow is as follows:
+
+              VCPU/IOThread
+                   |
+                   | (1)
+                   |
+                   V
+                Offload work              (2)
+      |-------> to threadlets -----------------------------> Helper thread
+      |            |                                               |
+      |            |                                               |
+      |            | (3)                                           | (4)
+      |            |                                               |
+      |         Handle other Guest requests                        |
+      |            |                                               |
+      |            |                                               V
+      |            | (3)                                  Signal the I/O Thread
+      |(6)         |                                               |
+      |            |                                              /
+      |            |                                             /
+      |            V                                            /
+      |          Do the post <---------------------------------/
+      |          processing               (5)
+      |            |
+      |            | (6)
+      |            V
+      |-Yes------ More async work?
+                   |
+                   | (7)
+	           No
+                   |
+                   |
+                   .
+                   .
+
+    Hence one needs to make sure that in the steps (3) and (4) which run in
+    parallel, any global data is accessed within only one context.
+
+Q.6: I have queued a threadlet which I want to cancel. How do I do that ?
+A.6: Threadlets framework provides the API cancel_threadlet:
+       - int cancel_threadletwork(ThreadletWork *work)
+
+     The API scans the ThreadletQueue to see if (work) is present. If it finds
+     work, it'll dequeue work and return 0.
+
+     On the other hand, if it does not find the (work) in the ThreadletQueue,
+     then it'll return 1. This can imply two things. Either the work is being
+     processed by one of the helper threads or it has been processed. The
+     threadlet infrastructure currently _does_not_ distinguish between these
+     two and the onus is on the caller to do that.
+
+Q.7: Apart from the global pool of threads, can I have my own private Queue ?
+A.7: Yes, the threadlets framework allows subsystems to create their own private
+     queues with associated pools of threads.
+
+     - Define a PrivateQueue
+       ThreadletQueue myQueue;
+
+     - Initialize it:
+       threadlet_queue_init(&myQueue, my_max_threads, my_min_threads);
+       where my_max_threads is the maximum number of threads that can be in the
+       thread pool and my_min_threads is the minimum number of active threads
+       that can be in the thread-pool.
+
+     - Submit work:
+       submit_threadletwork_to_queue(&myQueue, &my_work);
+
+     - Cancel work:
+       cancel_threadletwork_on_queue(&myQueue, &my_work);