Re: [RFC PATCH] logging: add a LOG_TCG_WARN for temp leaks

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 6/11/20 4:45 PM, Alex Bennée wrote:
> Pretty much all calls to qemu_log are either wrapped in some other
> enabling check or only enabled with debug defines. Add a specific flag
> for TCG warnings and expand the documentation of the qemu_log
> function.
> 
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> Cc: Peter Maydell <peter.maydell@linaro.org>
> ---
>  include/qemu/log-for-trace.h | 9 ++++++++-
>  include/qemu/log.h           | 2 ++
>  accel/tcg/translator.c       | 4 ++--
>  util/log.c                   | 2 ++
>  4 files changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/include/qemu/log-for-trace.h b/include/qemu/log-for-trace.h
> index 2f0a5b080ea..521d7936243 100644
> --- a/include/qemu/log-for-trace.h
> +++ b/include/qemu/log-for-trace.h
> @@ -29,7 +29,14 @@ static inline bool qemu_loglevel_mask(int mask)
>      return (qemu_loglevel & mask) != 0;
>  }
>  
> -/* main logging function */
> +/**
> + * qemu_log: main logging function
> + *
> + * Most users shouldn't be calling qemu_log unconditionally as it adds
> + * noise to logging output. Either use qemu_log_mask() or wrap
> + * successive log calls a qemu_loglevel_mask() check and
> + * qemu_log_lock/unlock(). The tracing infrastructure does similar wrapping.
> + */
>  int GCC_FMT_ATTR(1, 2) qemu_log(const char *fmt, ...);
>  
>  #endif
> diff --git a/include/qemu/log.h b/include/qemu/log.h
> index f4724f73301..e1574ef7c14 100644
> --- a/include/qemu/log.h
> +++ b/include/qemu/log.h
> @@ -64,6 +64,8 @@ static inline bool qemu_log_separate(void)
>  #define CPU_LOG_PLUGIN     (1 << 18)
>  /* LOG_STRACE is used for user-mode strace logging. */
>  #define LOG_STRACE         (1 << 19)
> +/* Additional TCG warnings */
> +#define LOG_TCG_WARN       (1 << 20)
>  
>  /* Lock output for a series of related logs.  Since this is not needed
>   * for a single qemu_log / qemu_log_mask / qemu_log_mask_and_addr, we
> diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c
> index 603d17ff831..44396ccd7ad 100644
> --- a/accel/tcg/translator.c
> +++ b/accel/tcg/translator.c
> @@ -26,8 +26,8 @@
>  void translator_loop_temp_check(DisasContextBase *db)
>  {
>      if (tcg_check_temp_count()) {
> -        qemu_log("warning: TCG temporary leaks before "
> -                 TARGET_FMT_lx "\n", db->pc_next);
> +        qemu_log_mask(LOG_TCG_WARN, "warning: TCG temporary leaks before "
> +                      TARGET_FMT_lx "\n", db->pc_next);

Why not replace by warn_report_once()?

>      }
>  }
>  
> diff --git a/util/log.c b/util/log.c
> index bdb3d712e88..fad25d9317f 100644
> --- a/util/log.c
> +++ b/util/log.c
> @@ -334,6 +334,8 @@ const QEMULogItem qemu_log_items[] = {
>  #endif
>      { LOG_STRACE, "strace",
>        "log every user-mode syscall, its input, and its result" },
> +    { LOG_TCG_WARN, "tcg",
> +      "log TCG warnings useful to developers." },
>      { 0, NULL, NULL },
>  };
>  
>