From: Stefan Hajnoczi <stefanha@redhat.com>

After iothread is enabled internally inside QEMU with GMainContext, we
may encounter this warning when destroying the iothread:

(qemu-system-x86_64:19925): GLib-CRITICAL **: g_source_remove_poll:
 assertion '!SOURCE_DESTROYED (source)' failed

The problem is that g_source_remove_poll() does not allow to remove one
source from array if the source is detached from its owner
context. (peterx: which IMHO does not make much sense)

Fix it on QEMU side by avoid calling g_source_remove_poll() if we know
the object is during destruction, and we won't leak anything after all
since the array will be gone soon cleanly even with that fd.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
[peterx: write the commit message]
Signed-off-by: Peter Xu <peterx@redhat.com>
---
 util/aio-posix.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/util/aio-posix.c b/util/aio-posix.c
index 2d51239ec6..5946ac09f0 100644
--- a/util/aio-posix.c
+++ b/util/aio-posix.c
@@ -223,7 +223,14 @@ void aio_set_fd_handler(AioContext *ctx,
             return;
         }
 
-        g_source_remove_poll(&ctx->source, &node->pfd);
+        /* If the GSource is in the process of being destroyed then
+         * g_source_remove_poll() causes an assertion failure.  Skip
+         * removal in that case, because glib cleans up its state during
+         * destruction anyway.
+         */
+        if (!g_source_is_destroyed(&ctx->source)) {
+            g_source_remove_poll(&ctx->source, &node->pfd);
+        }
 
         /* If the lock is held, just mark the node as deleted */
         if (qemu_lockcnt_count(&ctx->list_lock)) {
-- 
2.13.5

On Thu, 09/28 10:59, Peter Xu wrote:
> From: Stefan Hajnoczi <stefanha@redhat.com>
> 
> After iothread is enabled internally inside QEMU with GMainContext, we
> may encounter this warning when destroying the iothread:
> 
> (qemu-system-x86_64:19925): GLib-CRITICAL **: g_source_remove_poll:
>  assertion '!SOURCE_DESTROYED (source)' failed
> 
> The problem is that g_source_remove_poll() does not allow to remove one
> source from array if the source is detached from its owner
> context. (peterx: which IMHO does not make much sense)
> 
> Fix it on QEMU side by avoid calling g_source_remove_poll() if we know
> the object is during destruction, and we won't leak anything after all
> since the array will be gone soon cleanly even with that fd.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> [peterx: write the commit message]
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  util/aio-posix.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/util/aio-posix.c b/util/aio-posix.c
> index 2d51239ec6..5946ac09f0 100644
> --- a/util/aio-posix.c
> +++ b/util/aio-posix.c
> @@ -223,7 +223,14 @@ void aio_set_fd_handler(AioContext *ctx,
>              return;
>          }
>  
> -        g_source_remove_poll(&ctx->source, &node->pfd);
> +        /* If the GSource is in the process of being destroyed then
> +         * g_source_remove_poll() causes an assertion failure.  Skip
> +         * removal in that case, because glib cleans up its state during
> +         * destruction anyway.
> +         */
> +        if (!g_source_is_destroyed(&ctx->source)) {
> +            g_source_remove_poll(&ctx->source, &node->pfd);
> +        }
>  
>          /* If the lock is held, just mark the node as deleted */
>          if (qemu_lockcnt_count(&ctx->list_lock)) {
> -- 
> 2.13.5
> 

Reviewed-by: Fam Zheng <famz@redhat.com>

On Thu, Sep 28, 2017 at 10:59:58AM +0800, Peter Xu wrote:
> From: Stefan Hajnoczi <stefanha@redhat.com>
> 
> After iothread is enabled internally inside QEMU with GMainContext, we
> may encounter this warning when destroying the iothread:
> 
> (qemu-system-x86_64:19925): GLib-CRITICAL **: g_source_remove_poll:
>  assertion '!SOURCE_DESTROYED (source)' failed
> 
> The problem is that g_source_remove_poll() does not allow to remove one
> source from array if the source is detached from its owner
> context. (peterx: which IMHO does not make much sense)
> 
> Fix it on QEMU side by avoid calling g_source_remove_poll() if we know
> the object is during destruction, and we won't leak anything after all
> since the array will be gone soon cleanly even with that fd.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> [peterx: write the commit message]
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  util/aio-posix.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>