13973: Tweak test for inheriting CR priority

[arvados.git] / services / crunch-dispatch-slurm / squeue.go

diff --git a/services/crunch-dispatch-slurm/squeue.go b/services/crunch-dispatch-slurm/squeue.go
index 20305ab90abe91b150ae71a7749fd39c8e529548..0ce4fb6732f4d81bd03966c3857e0b975aa18769 100644 (file)
--- a/services/crunch-dispatch-slurm/squeue.go
+++ b/services/crunch-dispatch-slurm/squeue.go
@@ -78,9 +78,9 @@ func (sqc *SqueueChecker) SetPriority(uuid string, want int64) {
 // adjust slurm job nice values as needed to ensure slurm priority
 // order matches Arvados priority order.
 func (sqc *SqueueChecker) reniceAll() {
-       sqc.lock.RLock()
-       defer sqc.lock.RUnlock()
-
+       // This is slow (it shells out to scontrol many times) and no
+       // other goroutines update sqc.queue or any of the job fields
+       // we use here, so we don't acquire a lock.
        jobs := make([]*slurmJob, 0, len(sqc.queue))
        for _, j := range sqc.queue {
                if j.wantPriority == 0 {
@@ -139,9 +139,6 @@ func (sqc *SqueueChecker) Stop() {
 // queued). If it succeeds, it updates sqc.queue and wakes up any
 // goroutines that are waiting in HasUUID() or All().
 func (sqc *SqueueChecker) check() {
-       sqc.lock.Lock()
-       defer sqc.lock.Unlock()
-
        cmd := sqc.Slurm.QueueCommand([]string{"--all", "--noheader", "--format=%j %y %Q %T %r"})
        stdout, stderr := &bytes.Buffer{}, &bytes.Buffer{}
        cmd.Stdout, cmd.Stderr = stdout, stderr
@@ -162,6 +159,10 @@ func (sqc *SqueueChecker) check() {
                        log.Printf("warning: ignoring unparsed line in squeue output: %q", line)
                        continue
                }
+
+               // No other goroutines write to jobs' priority or nice
+               // fields, so we can read and write them without
+               // locks.
                replacing, ok := sqc.queue[uuid]
                if !ok {
                        replacing = &slurmJob{uuid: uuid}
@@ -197,7 +198,9 @@ func (sqc *SqueueChecker) check() {
                        log.Printf("warning: job %q has low priority %d, nice %d, state %q, reason %q", uuid, p, n, state, reason)
                }
        }
+       sqc.lock.Lock()
        sqc.queue = newq
+       sqc.lock.Unlock()
        sqc.notify.Broadcast()
 }