Yield thread group leader *Task in TaskSet.ForEachThreadGroup.

This makes this function usable from outside of the `kernel` package
without needing to call `tg.Leader()` (which requires a lock that
`TaskSet.ForEachThreadGroup` already acquires).

PiperOrigin-RevId: 720734630

pkg/sentry/kernel/sessions.go

@@ -198,7 +198,7 @@ func (pg *ProcessGroup) handleOrphan() {
 
 	// See if there are any stopped jobs.
 	hasStopped := false
-	pg.originator.pidns.owner.forEachThreadGroupLocked(func(tg *ThreadGroup) {
+	pg.originator.pidns.owner.forEachThreadGroupLocked(func(tg *ThreadGroup, _ *Task) {
 		if tg.processGroup != pg {
 			return
 		}
@@ -213,13 +213,13 @@ func (pg *ProcessGroup) handleOrphan() {
 	}
 
 	// Deliver appropriate signals to all thread groups.
-	pg.originator.pidns.owner.forEachThreadGroupLocked(func(tg *ThreadGroup) {
+	pg.originator.pidns.owner.forEachThreadGroupLocked(func(tg *ThreadGroup, tgLeader *Task) {
 		if tg.processGroup != pg {
 			return
 		}
 		tg.signalHandlers.mu.NestedLock(signalHandlersLockTg)
-		tg.leader.sendSignalLocked(SignalInfoPriv(linux.SIGHUP), true /* group */)
-		tg.leader.sendSignalLocked(SignalInfoPriv(linux.SIGCONT), true /* group */)
+		tgLeader.sendSignalLocked(SignalInfoPriv(linux.SIGHUP), true /* group */)
+		tgLeader.sendSignalLocked(SignalInfoPriv(linux.SIGCONT), true /* group */)
 		tg.signalHandlers.mu.NestedUnlock(signalHandlersLockTg)
 	})
 

pkg/sentry/kernel/threads.go

@@ -113,7 +113,7 @@ func newTaskSet(pidns *PIDNamespace) *TaskSet {
 }
 
 // ForEachThreadGroup applies f to each thread group in ts.
-func (ts *TaskSet) ForEachThreadGroup(f func(tg *ThreadGroup)) {
+func (ts *TaskSet) ForEachThreadGroup(f func(tg *ThreadGroup, tgLeader *Task)) {
 	ts.mu.RLock()
 	defer ts.mu.RUnlock()
 	ts.forEachThreadGroupLocked(f)
@@ -122,9 +122,9 @@ func (ts *TaskSet) ForEachThreadGroup(f func(tg *ThreadGroup)) {
 // forEachThreadGroupLocked applies f to each thread group in ts.
 //
 // Preconditions: ts.mu must be locked (for reading or writing).
-func (ts *TaskSet) forEachThreadGroupLocked(f func(tg *ThreadGroup)) {
+func (ts *TaskSet) forEachThreadGroupLocked(f func(tg *ThreadGroup, tgLeader *Task)) {
 	for tg := range ts.Root.tgids {
-		f(tg)
+		f(tg, tg.leader)
 	}
 }