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Tue, 11 Feb 2020 16:24:24 +0000 (UTC) Received: from lithium.redhat.com (ovpn-204-63.brq.redhat.com [10.40.204.63]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9889A26FB0; Tue, 11 Feb 2020 16:24:22 +0000 (UTC) From: Giuseppe Scrivano To: linux-kernel@vger.kernel.org Cc: rcu@vger.kernel.org, ebiederm@xmission.com, paulmck@kernel.org Subject: [PATCH] ipc: use a work queue to free_ipc Date: Tue, 11 Feb 2020 17:24:08 +0100 Message-Id: <20200211162408.2194037-1-gscrivan@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Content-Transfer-Encoding: quoted-printable Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org it avoids blocking on synchronize_rcu() in kern_umount(). the code: \#define _GNU_SOURCE \#include \#include \#include \#include int main() { int i; for (i =3D 0; i < 1000; i++) if (unshare (CLONE_NEWIPC) < 0) error (EXIT_FAILURE, errno, "unshare"); } gets 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 --- include/linux/ipc_namespace.h | 2 ++ ipc/namespace.c | 17 +++++++++++++++-- 2 files changed, 17 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; =20 + struct llist_node mnt_llist; + struct ns_common ns; } __randomize_layout; =20 diff --git a/ipc/namespace.c b/ipc/namespace.c index b3ca1476ca51..37d27e1b807a 100644 --- a/ipc/namespace.c +++ b/ipc/namespace.c @@ -117,6 +117,7 @@ void free_ipcs(struct ipc_namespace *ns, struct ipc_i= ds *ids, =20 static void free_ipc_ns(struct ipc_namespace *ns) { + mq_put_mnt(ns); sem_exit_ns(ns); msg_exit_ns(ns); shm_exit_ns(ns); @@ -127,6 +128,17 @@ static void free_ipc_ns(struct ipc_namespace *ns) kfree(ns); } =20 +static LLIST_HEAD(free_ipc_list); +static void free_ipc(struct work_struct *unused) +{ + struct llist_node *node =3D 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); +} +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 +160,9 @@ 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); } } =20 --=20 2.24.1