| Message ID | 20170705152855.GD19330@htj.duckdns.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
On Wed, 2017-07-05 at 11:28 -0400, Tejun Heo wrote: > Hello, Abdul. > > Thanks for the debug info. Can you please see whether the following > patch fixes the issue? It is my pleasure and yes the patch fixes the problem. > If the problem is too difficult to reproduce The problem was reproducible all the time. With the patch fix, I tried multiple times and long runs of cpu off-on cycles but no Oops is seen. Thank you for spending your valuable time on fixing this issue. Reported-and-tested-by : Abdul Haleem <abdhalee@linux.vnet.ibm.com> > to confirm the fix by seeing whether it no longer triggers, please let > me know. We can instead apply a patch which triggers WARN on the > failing condition to confirm the diagnosis. > > Thanks. > > diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h > index 793565c05742..8b4c3c2f2509 100644 > --- a/kernel/cgroup/cgroup-internal.h > +++ b/kernel/cgroup/cgroup-internal.h > @@ -33,6 +33,9 @@ struct cgroup_taskset { > struct list_head src_csets; > struct list_head dst_csets; > > + /* the number of tasks in the set */ > + int nr_tasks; > + > /* the subsys currently being processed */ > int ssid; > > diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c > index dbfd7028b1c6..e3c4152741a3 100644 > --- a/kernel/cgroup/cgroup.c > +++ b/kernel/cgroup/cgroup.c > @@ -1954,6 +1954,8 @@ static void cgroup_migrate_add_task(struct task_struct *task, > if (!cset->mg_src_cgrp) > return; > > + mgctx->tset.nr_tasks++; > + > list_move_tail(&task->cg_list, &cset->mg_tasks); > if (list_empty(&cset->mg_node)) > list_add_tail(&cset->mg_node, > @@ -2047,16 +2049,18 @@ static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx) > return 0; > > /* check that we can legitimately attach to the cgroup */ > - do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { > - if (ss->can_attach) { > - tset->ssid = ssid; > - ret = ss->can_attach(tset); > - if (ret) { > - failed_ssid = ssid; > - goto out_cancel_attach; > + if (tset->nr_tasks) { > + do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { > + if (ss->can_attach) { > + tset->ssid = ssid; > + ret = ss->can_attach(tset); > + if (ret) { > + failed_ssid = ssid; > + goto out_cancel_attach; > + } > } > - } > - } while_each_subsys_mask(); > + } while_each_subsys_mask(); > + } > > /* > * Now that we're guaranteed success, proceed to move all tasks to > @@ -2085,25 +2089,29 @@ static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx) > */ > tset->csets = &tset->dst_csets; > > - do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { > - if (ss->attach) { > - tset->ssid = ssid; > - ss->attach(tset); > - } > - } while_each_subsys_mask(); > + if (tset->nr_tasks) { > + do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { > + if (ss->attach) { > + tset->ssid = ssid; > + ss->attach(tset); > + } > + } while_each_subsys_mask(); > + } > > ret = 0; > goto out_release_tset; > > out_cancel_attach: > - do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { > - if (ssid == failed_ssid) > - break; > - if (ss->cancel_attach) { > - tset->ssid = ssid; > - ss->cancel_attach(tset); > - } > - } while_each_subsys_mask(); > + if (tset->nr_tasks) { > + do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { > + if (ssid == failed_ssid) > + break; > + if (ss->cancel_attach) { > + tset->ssid = ssid; > + ss->cancel_attach(tset); > + } > + } while_each_subsys_mask(); > + } > out_release_tset: > spin_lock_irq(&css_set_lock); > list_splice_init(&tset->dst_csets, &tset->src_csets); >
diff --git a/kernel/cgroup/cgroup-internal.h b/kernel/cgroup/cgroup-internal.h index 793565c05742..8b4c3c2f2509 100644 --- a/kernel/cgroup/cgroup-internal.h +++ b/kernel/cgroup/cgroup-internal.h @@ -33,6 +33,9 @@ struct cgroup_taskset { struct list_head src_csets; struct list_head dst_csets; + /* the number of tasks in the set */ + int nr_tasks; + /* the subsys currently being processed */ int ssid; diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index dbfd7028b1c6..e3c4152741a3 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1954,6 +1954,8 @@ static void cgroup_migrate_add_task(struct task_struct *task, if (!cset->mg_src_cgrp) return; + mgctx->tset.nr_tasks++; + list_move_tail(&task->cg_list, &cset->mg_tasks); if (list_empty(&cset->mg_node)) list_add_tail(&cset->mg_node, @@ -2047,16 +2049,18 @@ static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx) return 0; /* check that we can legitimately attach to the cgroup */ - do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { - if (ss->can_attach) { - tset->ssid = ssid; - ret = ss->can_attach(tset); - if (ret) { - failed_ssid = ssid; - goto out_cancel_attach; + if (tset->nr_tasks) { + do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { + if (ss->can_attach) { + tset->ssid = ssid; + ret = ss->can_attach(tset); + if (ret) { + failed_ssid = ssid; + goto out_cancel_attach; + } } - } - } while_each_subsys_mask(); + } while_each_subsys_mask(); + } /* * Now that we're guaranteed success, proceed to move all tasks to @@ -2085,25 +2089,29 @@ static int cgroup_migrate_execute(struct cgroup_mgctx *mgctx) */ tset->csets = &tset->dst_csets; - do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { - if (ss->attach) { - tset->ssid = ssid; - ss->attach(tset); - } - } while_each_subsys_mask(); + if (tset->nr_tasks) { + do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { + if (ss->attach) { + tset->ssid = ssid; + ss->attach(tset); + } + } while_each_subsys_mask(); + } ret = 0; goto out_release_tset; out_cancel_attach: - do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { - if (ssid == failed_ssid) - break; - if (ss->cancel_attach) { - tset->ssid = ssid; - ss->cancel_attach(tset); - } - } while_each_subsys_mask(); + if (tset->nr_tasks) { + do_each_subsys_mask(ss, ssid, mgctx->ss_mask) { + if (ssid == failed_ssid) + break; + if (ss->cancel_attach) { + tset->ssid = ssid; + ss->cancel_attach(tset); + } + } while_each_subsys_mask(); + } out_release_tset: spin_lock_irq(&css_set_lock); list_splice_init(&tset->dst_csets, &tset->src_csets);