Re: [PATCH] util/log: Close per-thread log file on thread termination

[Greg Kurz <groug@kaod.org>]

Cc'ing stable

On Fri, 21 Oct 2022 12:57:34 +0200
Greg Kurz <groug@kaod.org> wrote:

> When `-D ${logfile} -d tid` is passed, qemu_log_trylock() creates
> a dedicated log file for the current thread and opens it. The
> corresponding file descriptor is cached in a __thread variable.
> Nothing is done to close the corresponding file descriptor when the
> thread terminates though and the file descriptor is leaked.
> 
> The issue was found during code inspection and reproduced manually.
> 
> Fix that with an atexit notifier.
> 
> Fixes: 4e51069d6793 ("util/log: Support per-thread log files")
> Cc: richard.henderson@linaro.org
> Signed-off-by: Greg Kurz <groug@kaod.org>
> ---
>  util/log.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/util/log.c b/util/log.c
> index d6eb0378c3a3..39866bdaf2fa 100644
> --- a/util/log.c
> +++ b/util/log.c
> @@ -42,6 +42,7 @@ static QemuMutex global_mutex;
>  static char *global_filename;
>  static FILE *global_file;
>  static __thread FILE *thread_file;
> +static __thread Notifier qemu_log_thread_cleanup_notifier;
>  
>  int qemu_loglevel;
>  static bool log_append;
> @@ -77,6 +78,12 @@ static int log_thread_id(void)
>  #endif
>  }
>  
> +static void qemu_log_thread_cleanup(Notifier *n, void *unused)
> +{
> +    fclose(thread_file);
> +    thread_file = NULL;
> +}
> +
>  /* Lock/unlock output. */
>  
>  FILE *qemu_log_trylock(void)
> @@ -93,6 +100,8 @@ FILE *qemu_log_trylock(void)
>                  return NULL;
>              }
>              thread_file = logfile;
> +            qemu_log_thread_cleanup_notifier.notify = qemu_log_thread_cleanup;
> +            qemu_thread_atexit_add(&qemu_log_thread_cleanup_notifier);
>          } else {
>              rcu_read_lock();
>              /*