Re: [Qemu-devel] [PATCH 08/12] qemu-thread: report RCU quiescent states

[Paolo Bonzini]

Il 16/05/2013 10:33, liu ping fan ha scritto:
>> > +Luckily, in most cases no manual annotation is needed, because waiting
>> > +on condition variables (qemu_cond_wait), semaphores (qemu_sem_wait,
>> > +qemu_sem_timedwait) or events (qemu_event_wait) implicitly marks the 
>> > thread
>> > +as quiescent for the whole duration of the wait.  (There is an exception
>> > +for semaphore waits with a zero timeout).
>> > +
> Why not the same rule for zero timeout?
> 

Because they are not really doing synchronization, they are basically an
"atomic_dec_if_not_zero" on the semaphore count.

Paolo