Re: [Qemu-devel] [PATCH v3] async: aio_context_new(): Handle event_notifier_init failure

[Eric Blake]

On 09/16/2014 12:04 PM, Chrysostomos Nanakos wrote:
> If event_notifier_init fails QEMU exits without printing
> any error information to the user. This commit adds an error
> message on failure:
> 
>  # qemu [...]

Showing the actual command line you used would be helpful.

>  qemu: Failed to initialize event notifier: Too many open files in system
> 
> Signed-off-by: Chrysostomos Nanakos <address@hidden>
> ---
>  async.c                  |   16 +++++++++++-----
>  include/block/aio.h      |    2 +-
>  include/qemu/main-loop.h |    2 +-
>  iothread.c               |   11 ++++++++++-
>  main-loop.c              |    9 +++++++--
>  qemu-img.c               |    8 +++++++-
>  qemu-io.c                |    7 ++++++-
>  qemu-nbd.c               |    6 +++++-
>  tests/test-aio.c         |   10 +++++++++-
>  tests/test-thread-pool.c |   10 +++++++++-
>  tests/test-throttle.c    |   10 +++++++++-
>  vl.c                     |    5 +++--
>  12 files changed, 78 insertions(+), 18 deletions(-)
> 

> -AioContext *aio_context_new(void)
> +AioContext *aio_context_new(Error **errp)
>  {
> +    int ret;
>      AioContext *ctx;
>      ctx = (AioContext *) g_source_new(&aio_source_funcs, sizeof(AioContext));
> +    ret = event_notifier_init(&ctx->notifier, false);
> +    if (ret < 0) {
> +        g_source_destroy(&ctx->source);

Does g_source_destroy() guarantee that errno is unmolested? If not,

> +        error_setg_errno(errp, -ret, "Failed to initialize event notifier");

then this logs the wrong error. Swap the lines to be safe.

> +        return NULL;
> +    }
> +    aio_set_event_notifier(ctx, &ctx->notifier,
> +                           (EventNotifierHandler *)
> +                           event_notifier_test_and_clear);
>      ctx->pollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
>      ctx->thread_pool = NULL;
>      qemu_mutex_init(&ctx->bh_lock);
>      rfifolock_init(&ctx->lock, aio_rfifolock_cb, ctx);
> -    event_notifier_init(&ctx->notifier, false);

Is hoisting the event notifier init to occur before the mutex init going
to cause any grief?

> +++ b/main-loop.c

> @@ -138,8 +139,12 @@ int qemu_init_main_loop(void)
>          return ret;
>      }
>  
> +    qemu_aio_context = aio_context_new(&local_error);
> +    if (!qemu_aio_context) {
> +        error_propagate(errp, local_error);
> +        return -1;
> +    }

Can the earlier call to qemu_signal_init() consume any resources that
are now leaked?

> @@ -205,10 +206,17 @@ static void test_cancel(void)
>  int main(int argc, char **argv)
>  {
>      int ret;
> +    Error *local_error;
>  
>      init_clocks();
>  
> -    ctx = aio_context_new();
> +    ctx = aio_context_new(&local_error);
> +    if (!ctx) {
> +        error_report("Failed to create AIO Context: \'%s\'",

Use of \' inside "" is unusual. (Multiple times in your patch)

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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