From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: [PATCH 3/3] cgroup: clean up cgroup_serial_nr_cursor Date: Tue, 18 Jun 2013 11:18:35 -0700 Message-ID: <20130618181835.GC1596@htj.dyndns.org> References: <51C03AF2.7050702@huawei.com> <51C03B05.4080504@huawei.com> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=XJljqDnYlOkpRXkG9qwHTyM6I9gKKoDVYVgW7JJD/i8=; b=HhxT1Y9P6M+8tmN+nfliRgrxFMk307ZkcaqddogqUYdUwSY4oONGvDkfC/klKT43HL CwdErclHbCtaWaVF0GW8CBuZ9arYJ0seTSmxs9yCdMu43vY4iKjuDE75oouEXI5DfrRy UPhAg4FhKTCBPCoZM9dVfXO0eZ60LX/zfgr78P34AewmINv8942rOgMs8wFAYnexZKw9 UhDIlOw5TqRr8eOuy+yKVvW+u7iOZVPxg8aL0kyt/hwahnCNsocNicBCEVJoPB8z1Boi CrJEEXvySNSzMov/INBz18G9hoI67BZqD2X/UDKW50m5DPNnlCmBUSik3EHzsjI9AIzF LL7g== Content-Disposition: inline In-Reply-To: <51C03B05.4080504-hv44wF8Li93QT0dZR+AlfA@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Li Zefan Cc: LKML , cgroups >From 00356bd5f0f5e04183fb15805eb29e97c2fc20ac Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 18 Jun 2013 11:14:22 -0700 cgroup_serial_nr_cursor was created atomic64_t because I thought it was never gonna used for anything other than assigning unique numbers to cgroups and didn't want to worry about synchronization; however, now we're using it as an event-stamp to distinguish cgroups created before and after certain point which assumes that it's protected by cgroup_mutex. Let's make it clear by making it a u64. Also, rename it to cgroup_serial_nr_next and make it point to the next nr to allocate so that where it's pointing to is clear and more conventional. Signed-off-by: Tejun Heo Cc: Li Zefan --- Applied to cgroup/for-3.11 as a follow-up. Thanks. kernel/cgroup.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 0ed7d8d..65f333e 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -203,9 +203,10 @@ static struct cgroup_name root_cgroup_name = { .name = "/" }; * guarantees cgroups with bigger numbers are newer than those with smaller * numbers. Also, as cgroups are always appended to the parent's * ->children list, it guarantees that sibling cgroups are always sorted in - * the ascending serial number order on the list. + * the ascending serial number order on the list. Protected by + * cgroup_mutex. */ -static atomic64_t cgroup_serial_nr_cursor = ATOMIC64_INIT(0); +static u64 cgroup_serial_nr_next = 1; /* This flag indicates whether tasks in the fork and exit paths should * check for fork/exit handlers to call. This avoids us having to do @@ -2803,7 +2804,7 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss, struct super_block *sb = ss->root->sb; struct dentry *prev = NULL; struct inode *inode; - u64 update_upto; + u64 update_before; /* %NULL @cfts indicates abort and don't bother if @ss isn't attached */ if (!cfts || ss->root == &rootnode || @@ -2815,9 +2816,9 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss, /* * All cgroups which are created after we drop cgroup_mutex will * have the updated set of files, so we only need to update the - * cgroups created before the current @cgroup_serial_nr_cursor. + * cgroups created before the current @cgroup_serial_nr_next. */ - update_upto = atomic64_read(&cgroup_serial_nr_cursor); + update_before = cgroup_serial_nr_next; mutex_unlock(&cgroup_mutex); @@ -2844,7 +2845,7 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss, mutex_lock(&inode->i_mutex); mutex_lock(&cgroup_mutex); - if (cgrp->serial_nr <= update_upto && !cgroup_is_dead(cgrp)) + if (cgrp->serial_nr < update_before && !cgroup_is_dead(cgrp)) cgroup_addrm_files(cgrp, ss, cfts, is_add); mutex_unlock(&cgroup_mutex); mutex_unlock(&inode->i_mutex); @@ -4327,7 +4328,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, goto err_free_all; lockdep_assert_held(&dentry->d_inode->i_mutex); - cgrp->serial_nr = atomic64_inc_return(&cgroup_serial_nr_cursor); + cgrp->serial_nr = cgroup_serial_nr_next++; /* allocation complete, commit to creation */ list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children); -- 1.8.2.1