diff options
author | Giuseppe Scrivano <gscrivan@redhat.com> | 2020-06-08 06:40:10 +0200 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-06-08 20:05:56 +0200 |
commit | e1eb26fa62d04ec0955432be1aa8722a97cb52e7 (patch) | |
tree | 7321dbd441a768088a9c8e397ae540f1e9a26c1f | |
parent | ipc/msg: add missing annotation for freeque() (diff) | |
download | linux-e1eb26fa62d04ec0955432be1aa8722a97cb52e7.tar.xz linux-e1eb26fa62d04ec0955432be1aa8722a97cb52e7.zip |
ipc/namespace.c: use a work queue to free_ipc
the reason is to avoid a delay caused by the synchronize_rcu() call in
kern_umount() when the mqueue mount is freed.
the code:
#define _GNU_SOURCE
#include <sched.h>
#include <error.h>
#include <errno.h>
#include <stdlib.h>
int main()
{
int i;
for (i = 0; i < 1000; i++)
if (unshare(CLONE_NEWIPC) < 0)
error(EXIT_FAILURE, errno, "unshare");
}
goes from
Command being timed: "./ipc-namespace"
User time (seconds): 0.00
System time (seconds): 0.06
Percent of CPU this job got: 0%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:08.05
to
Command being timed: "./ipc-namespace"
User time (seconds): 0.00
System time (seconds): 0.02
Percent of CPU this job got: 96%
Elapsed (wall clock) time (h:mm:ss or m:ss): 0:00.03
Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Waiman Long <longman@redhat.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Manfred Spraul <manfred@colorfullife.com>
Link: http://lkml.kernel.org/r/20200225145419.527994-1-gscrivan@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | include/linux/ipc_namespace.h | 2 | ||||
-rw-r--r-- | ipc/namespace.c | 24 |
2 files changed, 24 insertions, 2 deletions
diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h index c309f43bde45..a06a78c67f19 100644 --- a/include/linux/ipc_namespace.h +++ b/include/linux/ipc_namespace.h @@ -68,6 +68,8 @@ struct ipc_namespace { struct user_namespace *user_ns; struct ucounts *ucounts; + struct llist_node mnt_llist; + struct ns_common ns; } __randomize_layout; diff --git a/ipc/namespace.c b/ipc/namespace.c index fdc3b5f3f53a..24e7b45320f7 100644 --- a/ipc/namespace.c +++ b/ipc/namespace.c @@ -117,6 +117,10 @@ void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids, static void free_ipc_ns(struct ipc_namespace *ns) { + /* mq_put_mnt() waits for a grace period as kern_unmount() + * uses synchronize_rcu(). + */ + mq_put_mnt(ns); sem_exit_ns(ns); msg_exit_ns(ns); shm_exit_ns(ns); @@ -127,6 +131,21 @@ static void free_ipc_ns(struct ipc_namespace *ns) kfree(ns); } +static LLIST_HEAD(free_ipc_list); +static void free_ipc(struct work_struct *unused) +{ + struct llist_node *node = llist_del_all(&free_ipc_list); + struct ipc_namespace *n, *t; + + llist_for_each_entry_safe(n, t, node, mnt_llist) + free_ipc_ns(n); +} + +/* + * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount. + */ +static DECLARE_WORK(free_ipc_work, free_ipc); + /* * put_ipc_ns - drop a reference to an ipc namespace. * @ns: the namespace to put @@ -148,8 +167,9 @@ void put_ipc_ns(struct ipc_namespace *ns) if (refcount_dec_and_lock(&ns->count, &mq_lock)) { mq_clear_sbinfo(ns); spin_unlock(&mq_lock); - mq_put_mnt(ns); - free_ipc_ns(ns); + + if (llist_add(&ns->mnt_llist, &free_ipc_list)) + schedule_work(&free_ipc_work); } } |