Re: [Qemu-devel] [PATCH] event_notifier: move to top-level directory

[Anthony Liguori <anthony@codemonkey.ws>]

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On 09/27/2011 10:28 AM, Jan Kiszka wrote:
> On 2011-09-27 17:17, Stefan Hajnoczi wrote:
>> On Tue, Sep 27, 2011 at 3:26 PM, Avi Kivity<avi@redhat.com>  wrote:
>>> Has no business in hw/.
>>>
>>> Signed-off-by: Avi Kivity<avi@redhat.com>
>>> ---
>>>   hw/event_notifier.c =>  event_notifier.c |    1 -
>>>   hw/event_notifier.h =>  event_notifier.h |    0
>>>   2 files changed, 0 insertions(+), 1 deletions(-)
>>>   rename hw/event_notifier.c =>  event_notifier.c (98%)
>>>   rename hw/event_notifier.h =>  event_notifier.h (100%)
>>
>> Yay.  Now perhaps we can kill qemu_eventfd(), whose users are
>> typically poking around with write(2) and read(2) when really they
>> could use the high-level event_notifier.h API.
>
> EventNotifiers will have to be superseded by something more generic
> first. It's not fully covering the use cases of cpus.c and
> posix-aio-compat.c.

Actually, for posix-aio, we can just switch to using g_idle_add().  g_idle_add() 
uses g_source_attach which is thread safe.  g_idle_add() gives you a thread safe 
mechanism to defer a piece of work to the main loop which is really what we want 
here.

This can actually be made to work with sync I/O emulation too by having another 
GMainLoop in the sync I/O loop although I thought I recalled a patch series to 
remove that stuff.

Kevin/Stefan, what's the plans for sync I/O emulation?

See untested patch below.

Regards,

Anthony Liguori

>
> Jan
>


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>From cf036a192f09ea76d89648b83ec84a4226d14172 Mon Sep 17 00:00:00 2001
From: Anthony Liguori <aliguori@us.ibm.com>
Date: Tue, 27 Sep 2011 11:01:51 -0500
Subject: [PATCH] posix-aio-compat: use g_idle_add()

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
 posix-aio-compat.c |   51 +++++++--------------------------------------------
 1 files changed, 7 insertions(+), 44 deletions(-)

diff --git a/posix-aio-compat.c b/posix-aio-compat.c
index d3c1174..1f746be 100644
--- a/posix-aio-compat.c
+++ b/posix-aio-compat.c
@@ -52,7 +52,6 @@ struct qemu_paiocb {
 };
 
 typedef struct PosixAioState {
-    int rfd, wfd;
     struct qemu_paiocb *first_aio;
 } PosixAioState;
 
@@ -466,7 +465,7 @@ static int qemu_paio_error(struct qemu_paiocb *aiocb)
     return ret;
 }
 
-static int posix_aio_process_queue(void *opaque)
+static gboolean posix_aio_process_queue(void *opaque)
 {
     PosixAioState *s = opaque;
     struct qemu_paiocb *acb, **pacb;
@@ -477,8 +476,9 @@ static int posix_aio_process_queue(void *opaque)
         pacb = &s->first_aio;
         for(;;) {
             acb = *pacb;
-            if (!acb)
-                return result;
+            if (!acb) {
+                goto out;
+            }
 
             ret = qemu_paio_error(acb);
             if (ret == ECANCELED) {
@@ -513,27 +513,8 @@ static int posix_aio_process_queue(void *opaque)
         }
     }
 
-    return result;
-}
-
-static void posix_aio_read(void *opaque)
-{
-    PosixAioState *s = opaque;
-    ssize_t len;
-
-    /* read all bytes from signal pipe */
-    for (;;) {
-        char bytes[16];
-
-        len = read(s->rfd, bytes, sizeof(bytes));
-        if (len == -1 && errno == EINTR)
-            continue; /* try again */
-        if (len == sizeof(bytes))
-            continue; /* more to read */
-        break;
-    }
-
-    posix_aio_process_queue(s);
+out:
+    return FALSE;
 }
 
 static int posix_aio_flush(void *opaque)
@@ -546,12 +527,7 @@ static PosixAioState *posix_aio_state;
 
 static void posix_aio_notify_event(void)
 {
-    char byte = 0;
-    ssize_t ret;
-
-    ret = write(posix_aio_state->wfd, &byte, sizeof(byte));
-    if (ret < 0 && errno != EAGAIN)
-        die("write()");
+    g_idle_add(posix_aio_process_queue, posix_aio_state);
 }
 
 static void paio_remove(struct qemu_paiocb *acb)
@@ -665,19 +641,6 @@ int paio_init(void)
     s = g_malloc(sizeof(PosixAioState));
 
     s->first_aio = NULL;
-    if (qemu_pipe(fds) == -1) {
-        fprintf(stderr, "failed to create pipe\n");
-        return -1;
-    }
-
-    s->rfd = fds[0];
-    s->wfd = fds[1];
-
-    fcntl(s->rfd, F_SETFL, O_NONBLOCK);
-    fcntl(s->wfd, F_SETFL, O_NONBLOCK);
-
-    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)
-- 
1.7.4.1