Am 05.10.2016 um 16:25 hat Paolo Bonzini geschrieben: > > > On 05/10/2016 16:20, Kevin Wolf wrote: > > Am 05.10.2016 um 15:55 hat Paolo Bonzini geschrieben: > >> On 05/10/2016 15:13, Stefan Hajnoczi wrote: > >>>> qemu_bh_delete is already clearing bh->scheduled at the same time > >>>> as it's setting bh->deleted. Since it's not using any memory > >>>> barriers, there is no synchronization going on for bh->deleted, > >>>> and this makes the bh->deleted checks superfluous in aio_compute_timeout, > >>>> aio_bh_poll and aio_ctx_check. > >>> > >>> Yikes. On one hand this sounds scary but in practice qemu_bh_delete() > >>> isn't called from another thread so the next aio_bh_poll() will indeed > >>> clean it up instead of dispatching a deleted BH. > >>> > >>> Due to the nature of this change I suggest making it in a separate > >>> patch. > >> > >> Separate from what? (Sorry if I'm being dense). > >> > >>>> > >>>> + * aio_bh_schedule_oneshot: Allocate a new bottom half structure that > >>>> will run > >>>> + * only once and as soon as possible. > >>>> + * > >>>> + * Bottom halves are lightweight callbacks whose invocation is > >>>> guaranteed > >>>> + * to be wait-free, thread-safe and signal-safe. The #QEMUBH structure > >>>> + * is opaque and must be allocated prior to its use. > >>> > >>> I'm confused. There is no QEMUBH structure in this function > >>> prototype. Is this comment from an earlier version of this function? > >> > >> No, it's from aio_bh_new. Of course this one is neither wait-free nor > >> signal-safe. Kevin, do you want me to respin? > > > > If the comment is wrong, either post a v2 of this patch or just reply > > with a new version of the comment and I'll squash it in. Your choice, I > > don't mind either way. > > Just removing those three lines would be okay.
Ok, done. Kevin
