Re: [PATCH] plugins/hotblocks: Fix potential deadlock in plugin_exit() function

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Hi Cong,

On 21/9/23 08:12, Cong Liu wrote:
> This patch fixes a potential deadlock in the plugin_exit() function of QEMU.
> The original code does not release the lock mutex if it is NULL. This patch
> adds a check for it being NULL and releases the mutex in that case.

You are correct.

> Signed-off-by: Cong Liu <liucong2@kylinos.cn>
> ---
>   contrib/plugins/hotblocks.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/contrib/plugins/hotblocks.c b/contrib/plugins/hotblocks.c
> index 6b74d25fead6..1f713f1904f3 100644
> --- a/contrib/plugins/hotblocks.c
> +++ b/contrib/plugins/hotblocks.c
> @@ -70,6 +70,8 @@ static void plugin_exit(qemu_plugin_id_t id, void *p)
>   
>           g_list_free(it);
>           g_mutex_unlock(&lock);
> +    } else {
> +        g_mutex_unlock(&lock);
>       }

The code stays simpler if you simply move the unlock call out
of the if() statement, here.

>   
>       qemu_plugin_outs(report->str);

Regards,

Phil.