From 0493fc983cc97eeb9c142ab7efcfce940f0cf75d Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Wed, 17 May 2017 13:09:21 +0200
Subject: [PATCH 15/27] curl: do not do aio_poll when waiting for a free
 CURLState

RH-Author: Paolo Bonzini <pbonzini@redhat.com>
Message-id: <20170517130921.27402-8-pbonzini@redhat.com>
Patchwork-id: 75266
O-Subject: [RHEL7.4 qemu-kvm PATCH v2 7/7] curl: do not do aio_poll when waiting for a free CURLState
Bugzilla: 1437393
RH-Acked-by: Max Reitz <mreitz@redhat.com>
RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
RH-Acked-by: Jeffrey Cody <jcody@redhat.com>

Instead, put the CURLAIOCB on a wait list and yield; curl_clean_state will
wake the corresponding coroutine.

Because of CURL's callback-based structure, we cannot easily convert
everything to CoMutex/CoQueue; keeping the QemuMutex is simpler.  However,
CoQueue is a simple wrapper around a linked list, so we can easily
use QSIMPLEQ and open-code a CoQueue, protected by the BDRVCURLState
QemuMutex instead of a CoMutex.

Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Message-id: 20170515100059.15795-8-pbonzini@redhat.com
Signed-off-by: Jeff Cody <jcody@redhat.com>
(cherry picked from commit 2bb5c936c5827e1d831002f7a7517cb8c2c2201d)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 block/curl.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/block/curl.c b/block/curl.c
index acfbe52..eb9fda7 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -98,6 +98,8 @@ typedef struct CURLAIOCB {
 
     size_t start;
     size_t end;
+
+    QSIMPLEQ_ENTRY(CURLAIOCB) next;
 } CURLAIOCB;
 
 typedef struct CURLSocket {
@@ -133,6 +135,7 @@ typedef struct BDRVCURLState {
     bool accept_range;
     AioContext *aio_context;
     QemuMutex mutex;
+    QSIMPLEQ_HEAD(, CURLAIOCB) free_state_waitq;
     char *username;
     char *password;
     char *proxyusername;
@@ -532,6 +535,7 @@ static int curl_init_state(BDRVCURLState *s, CURLState *state)
 /* Called with s->mutex held.  */
 static void curl_clean_state(CURLState *s)
 {
+    CURLAIOCB *next;
     int j;
     for (j = 0; j < CURL_NUM_ACB; j++) {
         assert(!s->acb[j]);
@@ -548,6 +552,14 @@ static void curl_clean_state(CURLState *s)
     }
 
     s->in_use = 0;
+
+    next = QSIMPLEQ_FIRST(&s->s->free_state_waitq);
+    if (next) {
+        QSIMPLEQ_REMOVE_HEAD(&s->s->free_state_waitq, next);
+        qemu_mutex_unlock(&s->s->mutex);
+        aio_co_wake(next->co);
+        qemu_mutex_lock(&s->s->mutex);
+    }
 }
 
 static void curl_parse_filename(const char *filename, QDict *options,
@@ -744,6 +756,7 @@ static int curl_open(BlockDriverState *bs, QDict *options, int flags,
     }
 
     DPRINTF("CURL: Opening %s\n", file);
+    QSIMPLEQ_INIT(&s->free_state_waitq);
     s->aio_context = bdrv_get_aio_context(bs);
     s->url = g_strdup(file);
     qemu_mutex_lock(&s->mutex);
@@ -844,8 +857,9 @@ static void curl_setup_preadv(BlockDriverState *bs, CURLAIOCB *acb)
         if (state) {
             break;
         }
+        QSIMPLEQ_INSERT_TAIL(&s->free_state_waitq, acb, next);
         qemu_mutex_unlock(&s->mutex);
-        aio_poll(bdrv_get_aio_context(bs), true);
+        qemu_coroutine_yield();
         qemu_mutex_lock(&s->mutex);
     }
 
-- 
1.8.3.1