The patch titled
Subject: cgroup: revert ss_id_lock to spinlock
has been added to the -mm tree. Its filename is
cgroup-revert-ss_id_lock-to-spinlock.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: cgroup: revert ss_id_lock to spinlock
Commit c1e2ee2dc436 "memcg: replace ss->id_lock with a rwlock" has now
been seen to cause the unfair behavior we should have expected from
converting a spinlock to an rwlock: softlockup in cgroup_mkdir(), whose
get_new_cssid() is waiting for the wlock, while there are 19 tasks using
the rlock in css_get_next() to get on with their memcg workload (in an
artificial test, admittedly). Yet lib/idr.c was made suitable for RCU way
back: revert that commit, restoring ss->id_lock to a spinlock.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Acked-by: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Acked-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/cgroup.h | 2 +-
kernel/cgroup.c | 18 +++++++++---------
2 files changed, 10 insertions(+), 10 deletions(-)
diff -puN include/linux/cgroup.h~cgroup-revert-ss_id_lock-to-spinlock include/linux/cgroup.h
--- a/include/linux/cgroup.h~cgroup-revert-ss_id_lock-to-spinlock
+++ a/include/linux/cgroup.h
@@ -535,7 +535,7 @@ struct cgroup_subsys {
struct list_head sibling;
/* used when use_id == true */
struct idr idr;
- rwlock_t id_lock;
+ spinlock_t id_lock;
/* should be defined only by modular subsystems */
struct module *module;
diff -puN kernel/cgroup.c~cgroup-revert-ss_id_lock-to-spinlock kernel/cgroup.c
--- a/kernel/cgroup.c~cgroup-revert-ss_id_lock-to-spinlock
+++ a/kernel/cgroup.c
@@ -4939,9 +4939,9 @@ void free_css_id(struct cgroup_subsys *s
rcu_assign_pointer(id->css, NULL);
rcu_assign_pointer(css->id, NULL);
- write_lock(&ss->id_lock);
+ spin_lock(&ss->id_lock);
idr_remove(&ss->idr, id->id);
- write_unlock(&ss->id_lock);
+ spin_unlock(&ss->id_lock);
kfree_rcu(id, rcu_head);
}
EXPORT_SYMBOL_GPL(free_css_id);
@@ -4967,10 +4967,10 @@ static struct css_id *get_new_cssid(stru
error = -ENOMEM;
goto err_out;
}
- write_lock(&ss->id_lock);
+ spin_lock(&ss->id_lock);
/* Don't use 0. allocates an ID of 1-65535 */
error = idr_get_new_above(&ss->idr, newid, 1, &myid);
- write_unlock(&ss->id_lock);
+ spin_unlock(&ss->id_lock);
/* Returns error when there are no free spaces for new ID.*/
if (error) {
@@ -4985,9 +4985,9 @@ static struct css_id *get_new_cssid(stru
return newid;
remove_idr:
error = -ENOSPC;
- write_lock(&ss->id_lock);
+ spin_lock(&ss->id_lock);
idr_remove(&ss->idr, myid);
- write_unlock(&ss->id_lock);
+ spin_unlock(&ss->id_lock);
err_out:
kfree(newid);
return ERR_PTR(error);
@@ -4999,7 +4999,7 @@ static int __init_or_module cgroup_init_
{
struct css_id *newid;
- rwlock_init(&ss->id_lock);
+ spin_lock_init(&ss->id_lock);
idr_init(&ss->idr);
newid = get_new_cssid(ss, 0);
@@ -5094,9 +5094,9 @@ css_get_next(struct cgroup_subsys *ss, i
* scan next entry from bitmap(tree), tmpid is updated after
* idr_get_next().
*/
- read_lock(&ss->id_lock);
+ spin_lock(&ss->id_lock);
tmp = idr_get_next(&ss->idr, &tmpid);
- read_unlock(&ss->id_lock);
+ spin_unlock(&ss->id_lock);
if (!tmp)
break;
_
Subject: Subject: cgroup: revert ss_id_lock to spinlock
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
proc-clear_refs-do-not-clear-reserved-pages.patch
mm-memcg-update-the-correct-soft-limit-tree-during-migration.patch
shm_unlock-fix-long-unpreemptible-section.patch
shm_unlock-fix-unevictable-pages-stranded-after-swap.patch
mm-fix-rss-count-leakage-during-migration.patch
mm-add-rss-counters-consistency-check.patch
mm-postpone-migrated-page-mapping-reset.patch
memcg-replace-mem_cont-by-mem_res_ctlr.patch
memcg-replace-mem-and-mem_cont-stragglers.patch
memcg-lru_size-instead-of-mem_cgroup_zstat.patch
memcg-enum-lru_list-lru.patch
memcg-remove-redundant-returns.patch
idr-make-idr_get_next-good-for-rcu_read_lock.patch
cgroup-revert-ss_id_lock-to-spinlock.patch
memcg-let-css_get_next-rely-upon-rcu_read_lock.patch
prio_tree-debugging-patch.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
