From e3796a245ad0efa65ca8d2dc6424562a8fbaeb6a Mon Sep 17 00:00:00 2001 From: John Snow Date: Thu, 16 Mar 2017 17:23:49 -0400 Subject: blockjob: add block_job_start_shim The purpose of this shim is to allow us to pause pre-started jobs. The purpose of *that* is to allow us to buffer a pause request that will be able to take effect before the job ever does any work, allowing us to create jobs during a quiescent state (under which they will be automatically paused), then resuming the jobs after the critical section in any order, either: (1) -block_job_start -block_job_resume (via e.g. drained_end) (2) -block_job_resume (via e.g. drained_end) -block_job_start The problem that requires a startup wrapper is the idea that a job must start in the busy=true state only its first time-- all subsequent entries require busy to be false, and the toggling of this state is otherwise handled during existing pause and yield points. The wrapper simply allows us to mandate that a job can "start," set busy to true, then immediately pause only if necessary. We could avoid requiring a wrapper, but all jobs would need to do it, so it's been factored out here. Signed-off-by: John Snow Reviewed-by: Jeff Cody Message-id: 20170316212351.13797-2-jsnow@redhat.com Signed-off-by: Jeff Cody --- blockjob.c | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) (limited to 'blockjob.c') diff --git a/blockjob.c b/blockjob.c index 2159df776b..0e9ed0336d 100644 --- a/blockjob.c +++ b/blockjob.c @@ -250,16 +250,28 @@ static bool block_job_started(BlockJob *job) return job->co; } +/** + * All jobs must allow a pause point before entering their job proper. This + * ensures that jobs can be paused prior to being started, then resumed later. + */ +static void coroutine_fn block_job_co_entry(void *opaque) +{ + BlockJob *job = opaque; + + assert(job && job->driver && job->driver->start); + block_job_pause_point(job); + job->driver->start(job); +} + void block_job_start(BlockJob *job) { assert(job && !block_job_started(job) && job->paused && - !job->busy && job->driver->start); - job->co = qemu_coroutine_create(job->driver->start, job); - if (--job->pause_count == 0) { - job->paused = false; - job->busy = true; - qemu_coroutine_enter(job->co); - } + job->driver && job->driver->start); + job->co = qemu_coroutine_create(block_job_co_entry, job); + job->pause_count--; + job->busy = true; + job->paused = false; + qemu_coroutine_enter(job->co); } void block_job_ref(BlockJob *job) -- cgit v1.2.1