[Qemu-devel] [RFC/ PATCH 2/2] qemu: Convert paio code to use the generic threading infrastructure.

[Gautham R Shenoy <ego@in.ibm.com>]

This patch makes the paio subsystem use the generic work offloading
infrastructure.

The patch has been tested with fstress.

Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
---
 posix-aio-compat.c |  156 ++++++++++------------------------------------------
 1 files changed, 30 insertions(+), 126 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index b43c531..1b405e4 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -28,6 +28,7 @@
 #include "block_int.h"
 
 #include "block/raw-posix-aio.h"
+#include "async-work.h"
 
 
 struct qemu_paiocb {
@@ -50,6 +51,7 @@ struct qemu_paiocb {
     struct qemu_paiocb *next;
 
     int async_context_id;
+    struct work_item *work;
 };
 
 typedef struct PosixAioState {
@@ -57,15 +59,8 @@ 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;
-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 struct async_queue aio_request_list;
 
 #ifdef CONFIG_PREADV
 static int preadv_present = 1;
@@ -84,39 +79,6 @@ 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;
@@ -300,47 +262,27 @@ static ssize_t handle_aiocb_rw(struct qemu_paiocb *aiocb)
     return nbytes;
 }
 
-static void *aio_thread(void *unused)
+static void aio_thread(struct work_item *work)
 {
-    pid_t pid;
 
-    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);
+    pid_t pid;
 
-        while (QTAILQ_EMPTY(&request_list) &&
-               !(ret == ETIMEDOUT)) {
-            ret = cond_timedwait(&cond, &lock, &ts);
-        }
+    struct qemu_paiocb *aiocb = (struct qemu_paiocb *) work->private;
+    ssize_t ret = 0;
 
-        if (QTAILQ_EMPTY(&request_list))
-            break;
+    pid = getpid();
 
-        aiocb = QTAILQ_FIRST(&request_list);
-        QTAILQ_REMOVE(&request_list, aiocb, node);
-        aiocb->active = 1;
-        idle_threads--;
-        mutex_unlock(&lock);
+    aiocb->active = 1;
 
-        switch (aiocb->aio_type & QEMU_AIO_TYPE_MASK) {
-        case QEMU_AIO_READ:
-        case QEMU_AIO_WRITE:
+    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:
+    case QEMU_AIO_FLUSH:
+        ret = handle_aiocb_flush(aiocb);
+        break;
+    case QEMU_AIO_IOCTL:
 		ret = handle_aiocb_ioctl(aiocb);
 		break;
 	default:
@@ -349,57 +291,29 @@ static void *aio_thread(void *unused)
 		break;
 	}
 
-        mutex_lock(&lock);
-        aiocb->ret = ret;
-        idle_threads++;
-        mutex_unlock(&lock);
-
-        if (kill(pid, aiocb->ev_signo)) die("kill failed");
-    }
-
-    idle_threads--;
-    cur_threads--;
-    mutex_unlock(&lock);
+    aiocb->ret = ret;
 
-    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);
-
-    if (sigprocmask(SIG_SETMASK, &oldset, NULL)) die("sigprocmask restore");
+    if (kill(pid, aiocb->ev_signo)) die("kill failed");
+    async_work_release(&aio_request_list, work);
 }
 
 static void qemu_paio_submit(struct qemu_paiocb *aiocb)
 {
+    struct work_item *work;
+
     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);
+
+    work = async_work_init(&aio_request_list, aio_thread, aiocb);
+    aiocb->work = work;
+    qemu_async_submit(&aio_request_list, work);
 }
 
 static ssize_t qemu_paio_return(struct qemu_paiocb *aiocb)
 {
     ssize_t ret;
 
-    mutex_lock(&lock);
     ret = aiocb->ret;
-    mutex_unlock(&lock);
-
     return ret;
 }
 
@@ -535,14 +449,14 @@ 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;
+        if (!qemu_async_cancel_work(&aio_request_list, acb->work))
+            acb->ret = -ECANCELED;
+         else
+            active = 1;
     } else if (acb->ret == -EINPROGRESS) {
         active = 1;
     }
-    mutex_unlock(&lock);
 
     if (active) {
         /* fail safe: if the aio could not be canceled, we wait for
@@ -615,7 +529,6 @@ int paio_init(void)
     struct sigaction act;
     PosixAioState *s;
     int fds[2];
-    int ret;
 
     if (posix_aio_state)
         return 0;
@@ -642,16 +555,7 @@ 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;
+    async_queue_init(&aio_request_list, max_threads, max_threads);
     return 0;
 }