Re: [PATCH] Remove support for CLOCK_MONOTONIC not being defined

[Paolo Bonzini <pbonzini@redhat.com>]

On 01/02/20 18:22, Peter Maydell wrote:
> Some older parts of QEMU's codebase assume that CLOCK_MONOTONIC
> might not be defined by the host OS, and have workarounds to
> deal with this. However, more recently (notably in commit
> 50290c002c045280f8d for qemu-img in mid-2019, but also much
> earlier in 2011 in commit 22795174a37e0 for ui/spice-display.c)
> we've written code that assumes CLOCK_MONOTONIC is always
> defined. The only host OS anybody's ever noticed this on
> is OSX 10.11 and earlier, which we don't support.
> 
> So we can assume that all our host OSes have the #define,
> and we can remove some now-unnecessary ifdefs.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
> I've left in the runtime-check in init_get_clock(), as it's
> less easy to see if the fallback there is ever used.
> ---
>  include/qemu/timer.h     |  5 +----
>  util/qemu-timer-common.c | 11 ++++-------
>  2 files changed, 5 insertions(+), 11 deletions(-)
> 
> diff --git a/include/qemu/timer.h b/include/qemu/timer.h
> index 85bc6eb00b2..6a8b48b5a9d 100644
> --- a/include/qemu/timer.h
> +++ b/include/qemu/timer.h
> @@ -838,14 +838,11 @@ extern int use_rt_clock;
>  
>  static inline int64_t get_clock(void)
>  {
> -#ifdef CLOCK_MONOTONIC
>      if (use_rt_clock) {
>          struct timespec ts;
>          clock_gettime(CLOCK_MONOTONIC, &ts);
>          return ts.tv_sec * 1000000000LL + ts.tv_nsec;
> -    } else
> -#endif
> -    {
> +    } else {
>          /* XXX: using gettimeofday leads to problems if the date
>             changes, so it should be avoided. */
>          return get_clock_realtime();
> diff --git a/util/qemu-timer-common.c b/util/qemu-timer-common.c
> index 06d084d3646..baf3317f745 100644
> --- a/util/qemu-timer-common.c
> +++ b/util/qemu-timer-common.c
> @@ -49,14 +49,11 @@ int use_rt_clock;
>  
>  static void __attribute__((constructor)) init_get_clock(void)
>  {
> +    struct timespec ts;
> +
>      use_rt_clock = 0;
> -#ifdef CLOCK_MONOTONIC
> -    {
> -        struct timespec ts;
> -        if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0) {
> -            use_rt_clock = 1;
> -        }
> +    if (clock_gettime(CLOCK_MONOTONIC, &ts) == 0) {
> +        use_rt_clock = 1;
>      }
> -#endif
>  }
>  #endif
> 

Queued, thanks.

Paolo