Re: [RFC 0/2] qemu-sem-posix: use monotonic clock instead

[Paolo Bonzini]

On 2/21/22 10:56, Longpeng(Mike) via wrote:
> The qemu_sem_timedwait() uses system time as default, it would be affected by
> changes to the system time. In the real scenario, the time that goes faster or
> slower is a common case and the NTP service could help us to sync time
> periodically.
>
> This patchset uses monotonic clock instead of the realtime clock, this could
> make sure we would not be affected by the system time anymore.

This looks good, I don't think there are cases where a more optimized 
semaphore is necessary (if there were, we could introduce a futex 
fallback on Linux).

However, pthread_condattr_t need not be in the struct.  The attributes 
can be allocated on the stack, because they do not have to remain alive 
after pthread_cond_init.

Thanks,

Paolo

> Longpeng (Mike) (2):
>    sem-posix: remove the posix semaphore support
>    sem-posix: use monotonic clock instead
>
>   include/qemu/thread-posix.h |  5 +--
>   meson.build                 | 12 ++++++-
>   util/qemu-thread-posix.c    | 82 +++++++++++++++------------------------------
>   3 files changed, 39 insertions(+), 60 deletions(-)