Re: [RFC 2/2] sem-posix: use monotonic clock instead

[Paolo Bonzini]

On 2/21/22 10:56, Longpeng(Mike) via wrote:
> +    long now_nsec;
> +#ifdef CONFIG_PTHREAD_CONDATTR_SETCLOCK
> +    struct timespec now;
> +    clock_gettime(CLOCK_MONOTONIC, &now);
> +    now_sec = now.tv_sec;
> +    now_nsec = now.tv_nsec;
> +#else
>       struct timeval tv;
>       gettimeofday(&tv, NULL);
> -    ts->tv_nsec = tv.tv_usec * 1000 + (ms % 1000) * 1000000;
> -    ts->tv_sec = tv.tv_sec + ms / 1000;
> +    now_sec = tv.tv_sec;
> +    now_nsec = tv.tv_usec * 1000;
> +#endif
> +

Perhaps this might minimize the amount of conditional code, too:

diff --git a/util/qemu-thread-posix.c b/util/qemu-thread-posix.c
index 903fa33965..4743d7b714 100644
--- a/util/qemu-thread-posix.c
+++ b/util/qemu-thread-posix.c
@@ -40,10 +40,14 @@ static void error_exit(int err, const char *msg)
 
 static void compute_abs_deadline(struct timespec *ts, int ms)
 {
-    struct timeval tv;
-    gettimeofday(&tv, NULL);
-    ts->tv_nsec = tv.tv_usec * 1000 + (ms % 1000) * 1000000;
-    ts->tv_sec = tv.tv_sec + ms / 1000;
+#ifdef CONFIG_PTHREAD_CONDATTR_SETCLOCK
+    clock_gettime(CLOCK_MONOTONIC, ts);
+#else
+    clock_gettime(CLOCK_REALTIME, ts);
+#endif
+
+    ts->tv_nsec += (ms % 1000) * 1000000;
+    ts->tv_sec += ms / 1000;
     if (ts->tv_nsec >= 1000000000) {
         ts->tv_sec++;
         ts->tv_nsec -= 1000000000;


Finally, the conditional variables initialization qemu_cond_init must
also use pthread_condattr_setclock.

Paolo