[Qemu-devel] [PATCH 0/6] v12: Threadlets: A generic task offloading framework.

[Qemu-devel] [PATCH 0/6] v12: Threadlets: A generic task offloading framework.

[Arun R Bharadwaj]

Hi,

This is the v12 of the refactored patch-series to have a generic
asynchronous task offloading framework (called threadlets)
within qemu.

I have run KVM autotest suite with this patch. This test suite
ran successfully for the following tests:
        -connecthon
        -ebizzy
        -dbench
        -fsstress
        -disktest
        -cpu_hotplug
        -hackbench
        -sleeptest

Changelog:

* Refactored the code in the following manner as asked by Anthony:
* Earlier Patch1 has been broken down into 4 patches:
        1) Make the necessary confiugation and Makefile changes.
        2) Move paio_cancel to new infrastructure and introduce
           only those APIs needed for this.
        3) Move paio_submit to new infrastructure and introduce
           only those APIs needed for this.
        4) Clean up posix-aio.compat.c off all the old code.

The following series implements...

---

Arun R Bharadwaj (5):
      Make the necessary changes in Makefile and configure file.
      Move paio_cancel() to new infrastructure.
      Move qemu_paio_submit() to the new infrastructure.
      Cleanup posix-aio.compat.c off all the old code.
      Move threadlets infrastructure to qemu-threadlets.c

Gautham R Shenoy (1):
      Add helper functions to enable virtio-9p make use of the threadlets


 Makefile.objs          |    3 -
 configure              |    2 
 docs/async-support.txt |  141 ++++++++++++++++++++++++++++++
 hw/virtio-9p.c         |  164 +++++++++++++++++++++++++++++++++++
 posix-aio-compat.c     |  225 +++++++++++-------------------------------------
 qemu-threadlets.c      |  189 ++++++++++++++++++++++++++++++++++++++++
 qemu-threadlets.h      |   47 ++++++++++
 vl.c                   |    3 +
 8 files changed, 596 insertions(+), 178 deletions(-)
 create mode 100644 docs/async-support.txt
 create mode 100644 qemu-threadlets.c
 create mode 100644 qemu-threadlets.h

-- 
arun

[Qemu-devel] [PATCH 1/6] Make the necessary changes in Makefile and configure file.

[Arun R Bharadwaj]

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
---
 Makefile.objs |    2 +-
 configure     |    2 --
 2 files changed, 1 insertions(+), 3 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/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 2/6] Move paio_cancel() to new infrastructure.

[Arun R Bharadwaj]

Move paio_cancel() to new infrastructure and introduce
the necessary APIs for this.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
---
 posix-aio-compat.c |   92 ++++++++++++++++++++++++++++++++++++++++++----------
 1 files changed, 74 insertions(+), 18 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 7b862b5..eb1e2db 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -27,9 +27,31 @@
 #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;
+
+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;
+
+static ThreadletQueue globalqueue;
 
 struct qemu_paiocb {
     BlockDriverAIOCB common;
@@ -51,6 +73,7 @@ struct qemu_paiocb {
     struct qemu_paiocb *next;
 
     int async_context_id;
+    ThreadletWork work;
 };
 
 typedef struct PosixAioState {
@@ -58,6 +81,45 @@ typedef struct PosixAioState {
     struct qemu_paiocb *first_aio;
 } PosixAioState;
 
+/**
+ * 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 the task is successfully cancelled.
+ *          1 otherwise.
+ */
+
+static int dequeue_work_on_queue(ThreadletQueue *queue, ThreadletWork *work)
+{
+    ThreadletWork *ret_work;
+    int ret = 1;
+
+    qemu_mutex_lock(&queue->lock);
+    QTAILQ_FOREACH(ret_work, &(queue->request_list), node) {
+        if (ret_work == work) {
+            QTAILQ_REMOVE(&queue->request_list, ret_work, node);
+            ret = 0;
+            break;
+        }
+    }
+    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 the task is successfully cancelled.
+ *          1 otherwise.
+ */
+
+static int dequeue_work(ThreadletWork *work)
+{
+    return dequeue_work_on_queue(&globalqueue, work);
+}
 
 static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
@@ -397,9 +459,9 @@ 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;
 }
@@ -534,22 +596,13 @@ static void paio_remove(struct qemu_paiocb *acb)
 static void paio_cancel(BlockDriverAIOCB *blockacb)
 {
     struct qemu_paiocb *acb = (struct qemu_paiocb *)blockacb;
-    int active = 0;
-
-    mutex_lock(&lock);
-    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 (dequeue_work(&acb->work) != 0) {
+        /* Wait for running work item to complete */
+        qemu_mutex_lock(&aiocb_mutex);
+        while (acb->ret == -EINPROGRESS) {
+            qemu_cond_wait(&aiocb_completion, &aiocb_mutex);
+        }
+        qemu_mutex_unlock(&aiocb_mutex);
     }
 
     paio_remove(acb);
@@ -623,6 +676,9 @@ 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 3/6] Move qemu_paio_submit() to the new infrastructure.

[Arun R Bharadwaj]

Move qemu_paio_submit() to the new infrastructure and
introduce the necessary APIs.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
---
 posix-aio-compat.c |  224 ++++++++++++++++++++++++++++++++++------------------
 1 files changed, 147 insertions(+), 77 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index eb1e2db..3f3c461 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -31,6 +31,9 @@
 
 #include "block/raw-posix-aio.h"
 
+#define MAX_GLOBAL_THREADS  64
+#define MIN_GLOBAL_THREADS   8
+
 static QemuMutex aiocb_mutex;
 static QemuCond aiocb_completion;
 
@@ -52,6 +55,7 @@ typedef struct ThreadletWork
 } ThreadletWork;
 
 static ThreadletQueue globalqueue;
+static int globalqueue_init;
 
 struct qemu_paiocb {
     BlockDriverAIOCB common;
@@ -81,6 +85,100 @@ typedef struct PosixAioState {
     struct qemu_paiocb *first_aio;
 } PosixAioState;
 
+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_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.
+ */
+
+static 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);
+}
+
+static void threadlet_queue_init(ThreadletQueue *queue,
+                          int max_threads, int min_threads);
+
+/**
+ * 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)
+{
+    if (!globalqueue_init) {
+        threadlet_queue_init(&globalqueue, MAX_GLOBAL_THREADS,
+                                MIN_GLOBAL_THREADS);
+        globalqueue_init = 1;
+    }
+
+    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.
@@ -121,6 +219,25 @@ static 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.
+ */
+
+static 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);
+}
+
 static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
 static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
 static pthread_t thread_id;
@@ -363,96 +480,49 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
     return nbytes;
 }
 
-static void *aio_thread(void *unused)
+static void aio_thread(ThreadletWork *work)
 {
     pid_t pid;
+    struct qemu_paiocb *aiocb = container_of(work, struct qemu_paiocb, work);
+    ssize_t ret = 0;
 
     pid = getpid();
 
-    while (1) {
-        struct qemu_paiocb *aiocb;
-        ssize_t ret = 0;
-        qemu_timeval tv;
-        struct timespec ts;
-
-        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);
-        }
-
-        if (QTAILQ_EMPTY(&request_list))
-            break;
-
-        aiocb = QTAILQ_FIRST(&request_list);
-        QTAILQ_REMOVE(&request_list, aiocb, node);
-        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;
-        }
-
-        mutex_lock(&lock);
-        aiocb->ret = ret;
-        idle_threads++;
-        mutex_unlock(&lock);
-
-        if (kill(pid, aiocb->ev_signo)) die("kill failed");
+    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);
-
-    return NULL;
-}
-
-static void spawn_thread(void)
-{
-    sigset_t set, oldset;
-
-    cur_threads++;
-    idle_threads++;
-
-    /* block all signals */
-    if (sigfillset(&set)) die("sigfillset");
-    if (sigprocmask(SIG_SETMASK, &set, &oldset)) die("sigprocmask");
-
-    thread_create(&thread_id, &attr, aio_thread, NULL);
+    qemu_mutex_lock(&aiocb_mutex);
+    aiocb->ret = ret;
+    qemu_cond_broadcast(&aiocb_completion);
+    qemu_mutex_unlock(&aiocb_mutex);
 
-    if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
+    if (kill(pid, aiocb->ev_signo)) {
+        die("kill failed");
+    }
 }
 
 static void qemu_paio_submit(struct qemu_paiocb *aiocb)
 {
+    qemu_mutex_lock(&aiocb_mutex);
     aiocb->ret = -EINPROGRESS;
-    aiocb->active = 0;
-    mutex_lock(&lock);
-    if (idle_threads == 0 && cur_threads < max_threads)
-        spawn_thread();
-    QTAILQ_INSERT_TAIL(&request_list, aiocb, node);
-    mutex_unlock(&lock);
-    cond_signal(&cond);
+    qemu_mutex_unlock(&aiocb_mutex);
+
+    aiocb->work.func = aio_thread;
+    submit_work(&aiocb->work);
 }
 
 static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)

[Qemu-devel] [PATCH 4/6] Cleanup posix-aio.compat.c off all the old code.

[Arun R Bharadwaj]

Cleanup posix-aio.compat.c off all the old code which
is now useless after introducing the generic threadlet
infrasturcture.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
---
 posix-aio-compat.c |   57 +---------------------------------------------------
 1 files changed, 1 insertions(+), 56 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 3f3c461..eb82fa4 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -70,10 +70,8 @@ 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;
@@ -238,19 +236,10 @@ static void threadlet_queue_init(ThreadletQueue *queue,
     qemu_cond_init(&queue->cond);
 }
 
-static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
-static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
-static pthread_t thread_id;
-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;
-
 #ifdef CONFIG_PREADV
 static int preadv_present = 1;
 #else
-static int preadv_present = 0;
+static int preadv_present;
 #endif
 
 static void die2(int err, const char *what)
@@ -264,39 +253,6 @@ 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)
-{
-    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;
@@ -741,7 +697,6 @@ int paio_init(void)
     struct sigaction act;
     PosixAioState *s;
     int fds[2];
-    int ret;
 
     if (posix_aio_state)
         return 0;
@@ -771,16 +726,6 @@ 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");
-
-    QTAILQ_INIT(&request_list);
-
     posix_aio_state = s;
     return 0;
 }

[Qemu-devel] [PATCH 5/6] Move threadlets infrastructure to qemu-threadlets.c

[Arun R Bharadwaj]

The reason for creating this generic infrastructure is so that other subsystems,
such as virtio-9p could make use of it for offloading tasks that could block.

Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Gautham R Shenoy <gautham.shenoy@gmail.com>
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>

Acked-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
---
 Makefile.objs          |    1 
 docs/async-support.txt |  141 ++++++++++++++++++++++++++++++++++++++
 posix-aio-compat.c     |  180 ------------------------------------------------
 qemu-threadlets.c      |  168 +++++++++++++++++++++++++++++++++++++++++++++
 qemu-threadlets.h      |   46 ++++++++++++
 5 files changed, 356 insertions(+), 180 deletions(-)
 create mode 100644 docs/async-support.txt
 create mode 100644 qemu-threadlets.c
 create mode 100644 qemu-threadlets.h

diff --git a/Makefile.objs b/Makefile.objs
index 3b7ec27..2cf8aba 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-threadlets.o
 block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
 block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
 
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);
diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index eb82fa4..20f53c7 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -27,36 +27,9 @@
 #include "qemu-common.h"
 #include "trace.h"
 #include "block_int.h"
-#include "qemu-thread.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;
-
-static ThreadletQueue globalqueue;
-static int globalqueue_init;
-
 struct qemu_paiocb {
     BlockDriverAIOCB common;
     int aio_fildes;
@@ -83,159 +56,6 @@ typedef struct PosixAioState {
     struct qemu_paiocb *first_aio;
 } PosixAioState;
 
-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_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.
- */
-
-static 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);
-}
-
-static void threadlet_queue_init(ThreadletQueue *queue,
-                          int max_threads, int min_threads);
-
-/**
- * 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)
-{
-    if (!globalqueue_init) {
-        threadlet_queue_init(&globalqueue, MAX_GLOBAL_THREADS,
-                                MIN_GLOBAL_THREADS);
-        globalqueue_init = 1;
-    }
-
-    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.
- *
- * Returns: 0 if the task is successfully cancelled.
- *          1 otherwise.
- */
-
-static int dequeue_work_on_queue(ThreadletQueue *queue, ThreadletWork *work)
-{
-    ThreadletWork *ret_work;
-    int ret = 1;
-
-    qemu_mutex_lock(&queue->lock);
-    QTAILQ_FOREACH(ret_work, &(queue->request_list), node) {
-        if (ret_work == work) {
-            QTAILQ_REMOVE(&queue->request_list, ret_work, node);
-            ret = 0;
-            break;
-        }
-    }
-    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 the task is successfully cancelled.
- *          1 otherwise.
- */
-
-static 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.
- */
-
-static 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);
-}
-
 #ifdef CONFIG_PREADV
 static int preadv_present = 1;
 #else
diff --git a/qemu-threadlets.c b/qemu-threadlets.c
new file mode 100644
index 0000000..23b4ecf
--- /dev/null
+++ b/qemu-threadlets.c
@@ -0,0 +1,168 @@
+/*
+ * 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-threadlets.h"
+#include "osdep.h"
+
+#define MAX_GLOBAL_THREADS  64
+#define MIN_GLOBAL_THREADS   8
+static ThreadletQueue globalqueue;
+static int globalqueue_init;
+
+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_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.
+ */
+void submit_work(ThreadletWork *work)
+{
+    if (!globalqueue_init) {
+        threadlet_queue_init(&globalqueue, MAX_GLOBAL_THREADS,
+                                MIN_GLOBAL_THREADS);
+        globalqueue_init = 1;
+    }
+
+    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.
+ *
+ * Returns: 0 if the task is successfully cancelled.
+ *          1 otherwise.
+ */
+int dequeue_work_on_queue(ThreadletQueue *queue, ThreadletWork *work)
+{
+    ThreadletWork *ret_work;
+    int ret = 1;
+
+    qemu_mutex_lock(&queue->lock);
+    QTAILQ_FOREACH(ret_work, &(queue->request_list), node) {
+        if (ret_work == work) {
+            QTAILQ_REMOVE(&queue->request_list, ret_work, node);
+            ret = 0;
+            break;
+        }
+    }
+    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 the task is successfully cancelled.
+ *          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-threadlets.h b/qemu-threadlets.h
new file mode 100644
index 0000000..39461a5
--- /dev/null
+++ b/qemu-threadlets.h
@@ -0,0 +1,46 @@
+/*
+ * 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>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * 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_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_queue_init(ThreadletQueue *queue, int max_threads,
+                          int min_threads);
+#endif

[Qemu-devel] [PATCH 6/6] Add helper functions to enable virtio-9p make use of the threadlets

[Arun R Bharadwaj]

From: Gautham R Shenoy <ego@in.ibm.com>

infrastructure for offloading blocking tasks such as making posix calls on
to the helper threads and handle the post_posix_operations() from the
context of the iothread. This frees the vcpu thread to process any other guest
operations while the processing of v9fs_io is in progress.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
---
 hw/virtio-9p.c     |  164 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 posix-aio-compat.c |   30 +++-------
 qemu-threadlets.c  |   21 +++++++
 qemu-threadlets.h  |    1 
 vl.c               |    3 +
 5 files changed, 196 insertions(+), 23 deletions(-)

diff --git a/hw/virtio-9p.c b/hw/virtio-9p.c
index 7c59988..88da20f 100644
--- a/hw/virtio-9p.c
+++ b/hw/virtio-9p.c
@@ -18,6 +18,7 @@
 #include "fsdev/qemu-fsdev.h"
 #include "virtio-9p-debug.h"
 #include "virtio-9p-xattr.h"
+#include "qemu-threadlets.h"
 
 int debug_9p_pdu;
 
@@ -33,6 +34,149 @@ enum {
     Oappend = 0x80,
 };
 
+typedef struct V9fsPostOp {
+    QTAILQ_ENTRY(V9fsPostOp) node;
+    void (*func)(void *arg);
+    void *arg;
+} V9fsPostOp;
+
+static struct {
+    int rfd;
+    int wfd;
+    QemuMutex lock;
+    QTAILQ_HEAD(, V9fsPostOp) post_op_list;
+} v9fs_async_struct;
+
+static void die2(int err, const char *what)
+{
+    fprintf(stderr, "%s failed: %s\n", what, strerror(err));
+    abort();
+}
+
+static void die(const char *what)
+{
+    die2(errno, what);
+}
+
+#define ASYNC_MAX_PROCESS   5
+
+/**
+ * v9fs_process_post_ops: Process any pending v9fs_post_posix_operation
+ * @arg: Not used.
+ *
+ * This function serves as a callback to the iothread to be called into whenever
+ * the v9fs_async_struct.wfd is written into. This thread goes through the list
+ * of v9fs_post_posix_operations() and executes them. In the process, it might
+ * queue more job on the asynchronous thread pool.
+ */
+static void v9fs_process_post_ops(void *arg)
+{
+    int count = 0;
+    struct V9fsPostOp *post_op;
+    int ret;
+    char byte;
+
+    do {
+        ret = read(v9fs_async_struct.rfd, &byte, sizeof(byte));
+    } while (ret > 0 || (ret == -1 && errno == EINTR));
+
+    qemu_mutex_lock(&v9fs_async_struct.lock);
+    for (count = 0; count < ASYNC_MAX_PROCESS; count++) {
+        if (QTAILQ_EMPTY(&(v9fs_async_struct.post_op_list))) {
+            break;
+        }
+        post_op = QTAILQ_FIRST(&(v9fs_async_struct.post_op_list));
+        QTAILQ_REMOVE(&(v9fs_async_struct.post_op_list), post_op, node);
+
+        qemu_mutex_unlock(&v9fs_async_struct.lock);
+        post_op->func(post_op->arg);
+        qemu_free(post_op);
+        qemu_mutex_lock(&v9fs_async_struct.lock);
+    }
+    qemu_mutex_unlock(&v9fs_async_struct.lock);
+}
+
+/**
+ * v9fs_async_signal: Inform the io-thread of completion of async job.
+ *
+ * This function is used to inform the iothread that a particular
+ * async-operation pertaining to v9fs has been completed and that the io thread
+ * can handle the v9fs_post_posix_operation.
+ *
+ * This is based on the aio_signal_handler
+ */
+static inline void v9fs_async_signal(void)
+{
+    char byte = 0;
+    ssize_t ret;
+    int tries = 0;
+
+    qemu_mutex_lock(&v9fs_async_struct.lock);
+    do {
+        assert(tries != 100);
+       ret = write(v9fs_async_struct.wfd, &byte, sizeof(byte));
+        tries++;
+    } while (ret < 0 && errno == EAGAIN);
+    qemu_mutex_unlock(&v9fs_async_struct.lock);
+
+    if (ret < 0 && errno != EAGAIN) {
+        die("write() in v9fs");
+    }
+
+    if (kill(getpid(), SIGUSR2)) {
+        die("kill failed");
+    }
+}
+
+/**
+ * v9fs_async_helper_done: Marks the completion of the v9fs_async job
+ * @func: v9fs_post_posix_func() for post-processing invoked in the context of
+ *        the io-thread
+ * @arg: Argument to func.
+ *
+ * This function is called from the context of one of the asynchronous threads
+ * in the thread pool. This is called when the asynchronous thread has finished
+ * executing a v9fs_posix_operation. It's purpose is to initiate the process of
+ * informing the io-thread that the v9fs_posix_operation has completed.
+ */
+static void v9fs_async_helper_done(void (*func)(void *arg), void *arg)
+{
+    struct V9fsPostOp *post_op;
+
+    post_op = qemu_mallocz(sizeof(*post_op));
+    post_op->func = func;
+    post_op->arg = arg;
+
+    qemu_mutex_lock(&v9fs_async_struct.lock);
+    QTAILQ_INSERT_TAIL(&(v9fs_async_struct.post_op_list), post_op, node);
+    qemu_mutex_unlock(&v9fs_async_struct.lock);
+
+    v9fs_async_signal();
+}
+
+/**
+ * v9fs_do_async_posix: Offload v9fs_posix_operation onto async thread.
+ * @vs: V9fsOPState variable for the OP operation.
+ * @posix_fn: The posix function which has to be offloaded onto async thread.
+ * @post_fn_ptr: Address of the location to hold the post_fn corresponding to
+ * the posix_fn
+ * @post_fn: The post processing function corresponding to the posix_fn.
+ *
+ * This function is a helper to offload posix_operation on to the asynchronous
+ * thread pool. It sets up the associations with the post_function that needs to
+ * be invoked by from the context of the iothread once the posix_fn has been
+ * executed.
+ */
+static void v9fs_do_async_posix(ThreadletWork *work ,
+                                void (*posix_fn)(ThreadletWork *work),
+                                void (**post_fn_ptr)(void *arg),
+                                void (*post_fn)(void *arg))
+{
+    *post_fn_ptr = post_fn;
+    work->func = posix_fn;
+    submit_work(work);
+}
+
 static int omode_to_uflags(int8_t mode)
 {
     int ret = 0;
@@ -3657,7 +3801,7 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)
     int i, len;
     struct stat stat;
     FsTypeEntry *fse;
-
+    int fds[2];
 
     s = (V9fsState *)virtio_common_init("virtio-9p",
                                     VIRTIO_ID_9P,
@@ -3740,5 +3884,23 @@ VirtIODevice *virtio_9p_init(DeviceState *dev, V9fsConf *conf)
                         s->tag_len;
     s->vdev.get_config = virtio_9p_get_config;
 
+    if (qemu_pipe(fds) == -1) {
+        fprintf(stderr, "failed to create fd's for virtio-9p\n");
+        exit(1);
+    }
+
+    v9fs_async_struct.rfd = fds[0];
+    v9fs_async_struct.wfd = fds[1];
+
+    fcntl(fds[0], F_SETFL, O_NONBLOCK);
+    fcntl(fds[1], F_SETFL, O_NONBLOCK);
+
+    qemu_set_fd_handler(fds[0], v9fs_process_post_ops, NULL, NULL);
+    QTAILQ_INIT(&v9fs_async_struct.post_op_list);
+    qemu_mutex_init(&(v9fs_async_struct.lock));
+
+    (void)v9fs_do_async_posix;
+    (void)v9fs_async_helper_done;
+
     return &s->vdev;
 }
diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index 20f53c7..9639aaa 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -256,11 +256,14 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
     return nbytes;
 }
 
+static PosixAioState *posix_aio_state;
+
 static void aio_thread(ThreadletWork *work)
 {
     pid_t pid;
     struct qemu_paiocb *aiocb = container_of(work, struct qemu_paiocb, work);
     ssize_t ret = 0;
+    char byte = 0;
 
     pid = getpid();
 
@@ -286,6 +289,11 @@ static void aio_thread(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");
     }
@@ -404,22 +412,6 @@ 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;
@@ -514,7 +506,6 @@ BlockDriverAIOCB *paio_ioctl(BlockDriverState *bs, int fd,
 
 int paio_init(void)
 {
-    struct sigaction act;
     PosixAioState *s;
     int fds[2];
 
@@ -526,11 +517,6 @@ 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-threadlets.c b/qemu-threadlets.c
index 23b4ecf..1e78f56 100644
--- a/qemu-threadlets.c
+++ b/qemu-threadlets.c
@@ -16,12 +16,28 @@
 
 #include "qemu-threadlets.h"
 #include "osdep.h"
+#include <signal.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();
+}
+
+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);
+}
+
 static void *threadlet_worker(void *data)
 {
     ThreadletQueue *queue = data;
@@ -166,3 +182,8 @@ void threadlet_queue_init(ThreadletQueue *queue,
     qemu_mutex_init(&queue->lock);
     qemu_cond_init(&queue->cond);
 }
+
+void threadlet_init(void)
+{
+   threadlet_register_signal_handler();
+}
diff --git a/qemu-threadlets.h b/qemu-threadlets.h
index 39461a5..f26c5b7 100644
--- a/qemu-threadlets.h
+++ b/qemu-threadlets.h
@@ -43,4 +43,5 @@ int dequeue_work_on_queue(ThreadletQueue *queue, ThreadletWork *work);
 int dequeue_work(ThreadletWork *work);
 void threadlet_queue_init(ThreadletQueue *queue, int max_threads,
                           int min_threads);
+void threadlet_init(void);
 #endif
diff --git a/vl.c b/vl.c
index df414ef..7b9a425 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-threadlets.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);

Re: [Qemu-devel] [PATCH 1/6] Make the necessary changes in Makefile and configure file.

[Stefan Hajnoczi]

The commit message "Make the necessary changes in Makefile and
configure file" provides no information, especially outside the
context of your patch series.  Please choose something more specific
about what the patch is doing.

CONFIG_POSIX=y excludes mingw32.  Does this commit break Windows
builds?  I suspect vnc_thread and io_thread may not be available on
Windows anyway.

Should we actually add qemu-thread.o where threadlets.o gets added
instead of putting it next to posix-aio-compat.o?

Stefan

Re: [Qemu-devel] [PATCH 2/6] Move paio_cancel() to new infrastructure.

[Stefan Hajnoczi]

On Thu, Nov 18, 2010 at 6:06 PM, Arun R Bharadwaj
<arun@linux.vnet.ibm.com> wrote:
> Move paio_cancel() to new infrastructure and introduce
> the necessary APIs for this.
>
> Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
> ---
>  posix-aio-compat.c |   92 ++++++++++++++++++++++++++++++++++++++++++----------
>  1 files changed, 74 insertions(+), 18 deletions(-)

This commit is not a safe step to make.  paio_cancel() is going to
cause uninitialized threadlet structures to be accessed.

You split the patches up into smaller commits for easier review.
Unfortunately this particular commit will result in a QEMU which
builds successfully but has undefined behavior at runtime - it may
crash or do random things.

That's a problem for git-bisect(1) and in general for anyone who
assumes they can build QEMU at an arbitrary point in the commit
history.  It's really important to preserve bisectability, because
once commits get introduced that build bad QEMUs we can no longer have
confidence in bisect!

Please split up commits so they introduce a new feature incrementally
but work properly at each step in the series.

Stefan

Re: [Qemu-devel] [PATCH 6/6] Add helper functions to enable virtio-9p make use of the threadlets

[Stefan Hajnoczi]

On Thu, Nov 18, 2010 at 6:07 PM, Arun R Bharadwaj
<arun@linux.vnet.ibm.com> wrote:
> From: Gautham R Shenoy <ego@in.ibm.com>
>
> infrastructure for offloading blocking tasks such as making posix calls on
> to the helper threads and handle the post_posix_operations() from the
> context of the iothread. This frees the vcpu thread to process any other guest
> operations while the processing of v9fs_io is in progress.
>
> Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
> Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
> Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
> ---
>  hw/virtio-9p.c     |  164 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  posix-aio-compat.c |   30 +++-------
>  qemu-threadlets.c  |   21 +++++++
>  qemu-threadlets.h  |    1
>  vl.c               |    3 +
>  5 files changed, 196 insertions(+), 23 deletions(-)

Is there code queued up which makes use of this in virtfs?  I ask
because at the moment this is deadcode.

If you are restructuring this patch series, perhaps move the signal
related changes into a commit - they are independent of virtfs.

Stefan

Re: [Qemu-devel] [PATCH 6/6] Add helper functions to enable virtio-9p make use of the threadlets

[Venkateswararao Jujjuri (JV)]

On 11/19/2010 2:17 AM, Stefan Hajnoczi wrote:
> On Thu, Nov 18, 2010 at 6:07 PM, Arun R Bharadwaj
> <arun@linux.vnet.ibm.com> wrote:
>> From: Gautham R Shenoy <ego@in.ibm.com>
>>
>> infrastructure for offloading blocking tasks such as making posix calls on
>> to the helper threads and handle the post_posix_operations() from the
>> context of the iothread. This frees the vcpu thread to process any other guest
>> operations while the processing of v9fs_io is in progress.
>>
>> Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
>> Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
>> Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
>> ---
>>  hw/virtio-9p.c     |  164 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  posix-aio-compat.c |   30 +++-------
>>  qemu-threadlets.c  |   21 +++++++
>>  qemu-threadlets.h  |    1
>>  vl.c               |    3 +
>>  5 files changed, 196 insertions(+), 23 deletions(-)
> 
> Is there code queued up which makes use of this in virtfs?  I ask
> because at the moment this is deadcode.
> 
> If you are restructuring this patch series, perhaps move the signal
> related changes into a commit - they are independent of virtfs.

Yep. Please separate out signal handling code and make that patch as part of
this series.
v9fs code should be part of separate patch series where we attempt to convert
v9fs function
calls to this threadlet model.

Thanks,
JV

> 
> Stefan
> 

Re: [Qemu-devel] [PATCH 5/6] Move threadlets infrastructure to qemu-threadlets.c

[Venkateswararao Jujjuri (JV)]

On 11/18/2010 10:07 AM, Arun R Bharadwaj wrote:
> The reason for creating this generic infrastructure is so that other subsystems,
> such as virtio-9p could make use of it for offloading tasks that could block.

If I read it right..this patch is nothing but reorganizing the code.
i.e moving the code out of posix-aio-compat.c into new files. Please make that
explicit
in the comment so that review becomes easy. :)

Thanks,
JV

> 
> Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> Signed-off-by: Gautham R Shenoy <gautham.shenoy@gmail.com>
> Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
> 
> Acked-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> ---
>  Makefile.objs          |    1 
>  docs/async-support.txt |  141 ++++++++++++++++++++++++++++++++++++++
>  posix-aio-compat.c     |  180 ------------------------------------------------
>  qemu-threadlets.c      |  168 +++++++++++++++++++++++++++++++++++++++++++++
>  qemu-threadlets.h      |   46 ++++++++++++
>  5 files changed, 356 insertions(+), 180 deletions(-)
>  create mode 100644 docs/async-support.txt
>  create mode 100644 qemu-threadlets.c
>  create mode 100644 qemu-threadlets.h
> 
> diff --git a/Makefile.objs b/Makefile.objs
> index 3b7ec27..2cf8aba 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-threadlets.o
>  block-obj-$(CONFIG_POSIX) += posix-aio-compat.o
>  block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
> 
> 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);
> diff --git a/posix-aio-compat.c b/posix-aio-compat.c
> index eb82fa4..20f53c7 100644
> --- a/posix-aio-compat.c
> +++ b/posix-aio-compat.c
> @@ -27,36 +27,9 @@
>  #include "qemu-common.h"
>  #include "trace.h"
>  #include "block_int.h"
> -#include "qemu-thread.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;
> -
> -static ThreadletQueue globalqueue;
> -static int globalqueue_init;
> -
>  struct qemu_paiocb {
>      BlockDriverAIOCB common;
>      int aio_fildes;
> @@ -83,159 +56,6 @@ typedef struct PosixAioState {
>      struct qemu_paiocb *first_aio;
>  } PosixAioState;
> 
> -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_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.
> - */
> -
> -static 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);
> -}
> -
> -static void threadlet_queue_init(ThreadletQueue *queue,
> -                          int max_threads, int min_threads);
> -
> -/**
> - * 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)
> -{
> -    if (!globalqueue_init) {
> -        threadlet_queue_init(&globalqueue, MAX_GLOBAL_THREADS,
> -                                MIN_GLOBAL_THREADS);
> -        globalqueue_init = 1;
> -    }
> -
> -    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.
> - *
> - * Returns: 0 if the task is successfully cancelled.
> - *          1 otherwise.
> - */
> -
> -static int dequeue_work_on_queue(ThreadletQueue *queue, ThreadletWork *work)
> -{
> -    ThreadletWork *ret_work;
> -    int ret = 1;
> -
> -    qemu_mutex_lock(&queue->lock);
> -    QTAILQ_FOREACH(ret_work, &(queue->request_list), node) {
> -        if (ret_work == work) {
> -            QTAILQ_REMOVE(&queue->request_list, ret_work, node);
> -            ret = 0;
> -            break;
> -        }
> -    }
> -    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 the task is successfully cancelled.
> - *          1 otherwise.
> - */
> -
> -static 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.
> - */
> -
> -static 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);
> -}
> -
>  #ifdef CONFIG_PREADV
>  static int preadv_present = 1;
>  #else
> diff --git a/qemu-threadlets.c b/qemu-threadlets.c
> new file mode 100644
> index 0000000..23b4ecf
> --- /dev/null
> +++ b/qemu-threadlets.c
> @@ -0,0 +1,168 @@
> +/*
> + * 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-threadlets.h"
> +#include "osdep.h"
> +
> +#define MAX_GLOBAL_THREADS  64
> +#define MIN_GLOBAL_THREADS   8
> +static ThreadletQueue globalqueue;
> +static int globalqueue_init;
> +
> +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_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.
> + */
> +void submit_work(ThreadletWork *work)
> +{
> +    if (!globalqueue_init) {
> +        threadlet_queue_init(&globalqueue, MAX_GLOBAL_THREADS,
> +                                MIN_GLOBAL_THREADS);
> +        globalqueue_init = 1;
> +    }
> +
> +    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.
> + *
> + * Returns: 0 if the task is successfully cancelled.
> + *          1 otherwise.
> + */
> +int dequeue_work_on_queue(ThreadletQueue *queue, ThreadletWork *work)
> +{
> +    ThreadletWork *ret_work;
> +    int ret = 1;
> +
> +    qemu_mutex_lock(&queue->lock);
> +    QTAILQ_FOREACH(ret_work, &(queue->request_list), node) {
> +        if (ret_work == work) {
> +            QTAILQ_REMOVE(&queue->request_list, ret_work, node);
> +            ret = 0;
> +            break;
> +        }
> +    }
> +    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 the task is successfully cancelled.
> + *          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-threadlets.h b/qemu-threadlets.h
> new file mode 100644
> index 0000000..39461a5
> --- /dev/null
> +++ b/qemu-threadlets.h
> @@ -0,0 +1,46 @@
> +/*
> + * 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>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * 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_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_queue_init(ThreadletQueue *queue, int max_threads,
> +                          int min_threads);
> +#endif
> 
> 

Re: [Qemu-devel] [PATCH 2/6] Move paio_cancel() to new infrastructure.

[Venkateswararao Jujjuri (JV)]

On 11/19/2010 2:07 AM, Stefan Hajnoczi wrote:
> On Thu, Nov 18, 2010 at 6:06 PM, Arun R Bharadwaj
> <arun@linux.vnet.ibm.com> wrote:
>> Move paio_cancel() to new infrastructure and introduce
>> the necessary APIs for this.
>>
>> Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
>> ---
>>  posix-aio-compat.c |   92 ++++++++++++++++++++++++++++++++++++++++++----------
>>  1 files changed, 74 insertions(+), 18 deletions(-)
> 
> This commit is not a safe step to make.  paio_cancel() is going to
> cause uninitialized threadlet structures to be accessed.
> 
> You split the patches up into smaller commits for easier review.
> Unfortunately this particular commit will result in a QEMU which
> builds successfully but has undefined behavior at runtime - it may
> crash or do random things.
> 
> That's a problem for git-bisect(1) and in general for anyone who
> assumes they can build QEMU at an arbitrary point in the commit
> history.  It's really important to preserve bisectability, because
> once commits get introduced that build bad QEMUs we can no longer have
> confidence in bisect!
> 
> Please split up commits so they introduce a new feature incrementally
> but work properly at each step in the series.

Arun, you may move this to later part of the series to take care of this bisect
issue.

Thanks,
JV

> 
> Stefan
> 

Re: [Qemu-devel] [PATCH 3/6] Move qemu_paio_submit() to the new infrastructure.

[Venkateswararao Jujjuri (JV)]

On 11/18/2010 10:07 AM, Arun R Bharadwaj wrote:
> Move qemu_paio_submit() to the new infrastructure and
> introduce the necessary APIs.
> 
> Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>

Looks good to me.

Acked-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>

> ---
>  posix-aio-compat.c |  224 ++++++++++++++++++++++++++++++++++------------------
>  1 files changed, 147 insertions(+), 77 deletions(-)
> 
> diff --git a/posix-aio-compat.c b/posix-aio-compat.c
> index eb1e2db..3f3c461 100644
> --- a/posix-aio-compat.c
> +++ b/posix-aio-compat.c
> @@ -31,6 +31,9 @@
> 
>  #include "block/raw-posix-aio.h"
> 
> +#define MAX_GLOBAL_THREADS  64
> +#define MIN_GLOBAL_THREADS   8
> +
>  static QemuMutex aiocb_mutex;
>  static QemuCond aiocb_completion;
> 
> @@ -52,6 +55,7 @@ typedef struct ThreadletWork
>  } ThreadletWork;
> 
>  static ThreadletQueue globalqueue;
> +static int globalqueue_init;
> 
>  struct qemu_paiocb {
>      BlockDriverAIOCB common;
> @@ -81,6 +85,100 @@ typedef struct PosixAioState {
>      struct qemu_paiocb *first_aio;
>  } PosixAioState;
> 
> +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_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.
> + */
> +
> +static 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);
> +}
> +
> +static void threadlet_queue_init(ThreadletQueue *queue,
> +                          int max_threads, int min_threads);
> +
> +/**
> + * 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)
> +{
> +    if (!globalqueue_init) {
> +        threadlet_queue_init(&globalqueue, MAX_GLOBAL_THREADS,
> +                                MIN_GLOBAL_THREADS);
> +        globalqueue_init = 1;
> +    }
> +
> +    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.
> @@ -121,6 +219,25 @@ static 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.
> + */
> +
> +static 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);
> +}
> +
>  static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
>  static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
>  static pthread_t thread_id;
> @@ -363,96 +480,49 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
>      return nbytes;
>  }
> 
> -static void *aio_thread(void *unused)
> +static void aio_thread(ThreadletWork *work)
>  {
>      pid_t pid;
> +    struct qemu_paiocb *aiocb = container_of(work, struct qemu_paiocb, work);
> +    ssize_t ret = 0;
> 
>      pid = getpid();
> 
> -    while (1) {
> -        struct qemu_paiocb *aiocb;
> -        ssize_t ret = 0;
> -        qemu_timeval tv;
> -        struct timespec ts;
> -
> -        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);
> -        }
> -
> -        if (QTAILQ_EMPTY(&request_list))
> -            break;
> -
> -        aiocb = QTAILQ_FIRST(&request_list);
> -        QTAILQ_REMOVE(&request_list, aiocb, node);
> -        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;
> -        }
> -
> -        mutex_lock(&lock);
> -        aiocb->ret = ret;
> -        idle_threads++;
> -        mutex_unlock(&lock);
> -
> -        if (kill(pid, aiocb->ev_signo)) die("kill failed");
> +    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);
> -
> -    return NULL;
> -}
> -
> -static void spawn_thread(void)
> -{
> -    sigset_t set, oldset;
> -
> -    cur_threads++;
> -    idle_threads++;
> -
> -    /* block all signals */
> -    if (sigfillset(&set)) die("sigfillset");
> -    if (sigprocmask(SIG_SETMASK, &set, &oldset)) die("sigprocmask");
> -
> -    thread_create(&thread_id, &attr, aio_thread, NULL);
> +    qemu_mutex_lock(&aiocb_mutex);
> +    aiocb->ret = ret;
> +    qemu_cond_broadcast(&aiocb_completion);
> +    qemu_mutex_unlock(&aiocb_mutex);
> 
> -    if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
> +    if (kill(pid, aiocb->ev_signo)) {
> +        die("kill failed");
> +    }
>  }
> 
>  static void qemu_paio_submit(struct qemu_paiocb *aiocb)
>  {
> +    qemu_mutex_lock(&aiocb_mutex);
>      aiocb->ret = -EINPROGRESS;
> -    aiocb->active = 0;
> -    mutex_lock(&lock);
> -    if (idle_threads == 0 && cur_threads < max_threads)
> -        spawn_thread();
> -    QTAILQ_INSERT_TAIL(&request_list, aiocb, node);
> -    mutex_unlock(&lock);
> -    cond_signal(&cond);
> +    qemu_mutex_unlock(&aiocb_mutex);
> +
> +    aiocb->work.func = aio_thread;
> +    submit_work(&aiocb->work);
>  }
> 
>  static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)
> 
> 

Re: [Qemu-devel] [PATCH 4/6] Cleanup posix-aio.compat.c off all the old code.

[Venkateswararao Jujjuri (JV)]

On 11/18/2010 10:07 AM, Arun R Bharadwaj wrote:
> Cleanup posix-aio.compat.c off all the old code which
> is now useless after introducing the generic threadlet
> infrasturcture.
> 
> Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>

Looks good to me.

Acked-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>

> ---
>  posix-aio-compat.c |   57 +---------------------------------------------------
>  1 files changed, 1 insertions(+), 56 deletions(-)
> 
> diff --git a/posix-aio-compat.c b/posix-aio-compat.c
> index 3f3c461..eb82fa4 100644
> --- a/posix-aio-compat.c
> +++ b/posix-aio-compat.c
> @@ -70,10 +70,8 @@ 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;
> @@ -238,19 +236,10 @@ static void threadlet_queue_init(ThreadletQueue *queue,
>      qemu_cond_init(&queue->cond);
>  }
> 
> -static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
> -static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
> -static pthread_t thread_id;
> -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;
> -
>  #ifdef CONFIG_PREADV
>  static int preadv_present = 1;
>  #else
> -static int preadv_present = 0;
> +static int preadv_present;
>  #endif
> 
>  static void die2(int err, const char *what)
> @@ -264,39 +253,6 @@ 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)
> -{
> -    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;
> @@ -741,7 +697,6 @@ int paio_init(void)
>      struct sigaction act;
>      PosixAioState *s;
>      int fds[2];
> -    int ret;
> 
>      if (posix_aio_state)
>          return 0;
> @@ -771,16 +726,6 @@ 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");
> -
> -    QTAILQ_INIT(&request_list);
> -
>      posix_aio_state = s;
>      return 0;
>  }
> 
>