On 14/06/2016 20:17, Stefan Hajnoczi wrote: > Block jobs are coroutines that usually perform I/O but sometimes also > sleep or yield. Currently only sleeping or yielded block jobs can be > paused. This means jobs that do not sleep or yield (using > block_job_yield()) are unaffected by block_job_pause(). > > Add block_job_pause_point() so that block jobs can mark quiescent points > that are suitable for pausing. This solves the problem that it can take > a block job a long time to pause if it is performing a long series of > I/O operations. > > Transitioning to paused state involves a .pause()/.resume() callback. > These callbacks are used to ensure that I/O and event loop activity has > ceased while the job is at a pause point. > > Note that this patch introduces a stricter pause state than previously. > The job->busy flag was incorrectly documented as a quiescent state > without I/O pending. This is violated by any job that has I/O pending > across sleep or block_job_yield(), like the mirror block job.
Right, we should document job->busy as a quiescent state where no one will re-enter the coroutine. Paolo
