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[Qemu-block] [PULL 3/8] curl: never invoke callbacks with s->mutex held


From: Jeff Cody
Subject: [Qemu-block] [PULL 3/8] curl: never invoke callbacks with s->mutex held
Date: Tue, 16 May 2017 11:54:15 -0400

From: Paolo Bonzini <address@hidden>

All curl callbacks go through curl_multi_do, and hence are called with
s->mutex held.  Note that with comments, and make curl_read_cb drop the
lock before invoking the callback.

Likewise for curl_find_buf, where the callback can be invoked by the
caller.

Cc: address@hidden
Reviewed-by: Jeff Cody <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
Reviewed-by: Max Reitz <address@hidden>
Message-id: address@hidden
Signed-off-by: Jeff Cody <address@hidden>
---
 block/curl.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/block/curl.c b/block/curl.c
index 562340f..18b82bc 100644
--- a/block/curl.c
+++ b/block/curl.c
@@ -148,6 +148,7 @@ static void curl_multi_do(void *arg);
 static void curl_multi_read(void *arg);
 
 #ifdef NEED_CURL_TIMER_CALLBACK
+/* Called from curl_multi_do_locked, with s->mutex held.  */
 static int curl_timer_cb(CURLM *multi, long timeout_ms, void *opaque)
 {
     BDRVCURLState *s = opaque;
@@ -164,6 +165,7 @@ static int curl_timer_cb(CURLM *multi, long timeout_ms, 
void *opaque)
 }
 #endif
 
+/* Called from curl_multi_do_locked, with s->mutex held.  */
 static int curl_sock_cb(CURL *curl, curl_socket_t fd, int action,
                         void *userp, void *sp)
 {
@@ -213,6 +215,7 @@ static int curl_sock_cb(CURL *curl, curl_socket_t fd, int 
action,
     return 0;
 }
 
+/* Called from curl_multi_do_locked, with s->mutex held.  */
 static size_t curl_header_cb(void *ptr, size_t size, size_t nmemb, void 
*opaque)
 {
     BDRVCURLState *s = opaque;
@@ -227,6 +230,7 @@ static size_t curl_header_cb(void *ptr, size_t size, size_t 
nmemb, void *opaque)
     return realsize;
 }
 
+/* Called from curl_multi_do_locked, with s->mutex held.  */
 static size_t curl_read_cb(void *ptr, size_t size, size_t nmemb, void *opaque)
 {
     CURLState *s = ((CURLState*)opaque);
@@ -265,7 +269,9 @@ static size_t curl_read_cb(void *ptr, size_t size, size_t 
nmemb, void *opaque)
                                   request_length - offset);
             }
 
+            qemu_mutex_unlock(&s->s->mutex);
             acb->common.cb(acb->common.opaque, 0);
+            qemu_mutex_lock(&s->s->mutex);
             qemu_aio_unref(acb);
             s->acb[i] = NULL;
         }
@@ -306,8 +312,6 @@ static int curl_find_buf(BDRVCURLState *s, size_t start, 
size_t len,
             if (clamped_len < len) {
                 qemu_iovec_memset(acb->qiov, clamped_len, 0, len - 
clamped_len);
             }
-            acb->common.cb(acb->common.opaque, 0);
-
             return FIND_RET_OK;
         }
 
@@ -854,8 +858,8 @@ static void curl_readv_bh_cb(void *p)
     // we can just call the callback and be done.
     switch (curl_find_buf(s, start, acb->nb_sectors * BDRV_SECTOR_SIZE, acb)) {
         case FIND_RET_OK:
-            qemu_aio_unref(acb);
-            // fall through
+            ret = 0;
+            goto out;
         case FIND_RET_WAIT:
             goto out;
         default:
-- 
2.9.3




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