Messages in this thread | | | Date | Thu, 18 Sep 2008 20:28:25 -0700 | From | Balbir Singh <> | Subject | Re: [PATCH -mm] memrlimit: fix task_lock() recursive locking (v2) |
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Andrea Righi wrote:
> Since we hold task_lock(), we know that p->mm cannot change and we don't have > to worry about incrementing mm_users. So, just use p->mm directly and > check that we've not picked a kernel thread. > > Signed-off-by: Andrea Righi <righi.andrea@gmail.com> > --- > kernel/cgroup.c | 3 ++- > mm/memrlimitcgroup.c | 10 ++++------ > 2 files changed, 6 insertions(+), 7 deletions(-) > > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > index 678a680..03cc925 100644 > --- a/kernel/cgroup.c > +++ b/kernel/cgroup.c > @@ -2757,7 +2757,8 @@ void cgroup_fork_callbacks(struct task_struct *child) > * invoke this routine, since it assigns the mm->owner the first time > * and does not change it. > * > - * The callbacks are invoked with mmap_sem held in read mode. > + * The callbacks are invoked with task_lock held and mmap_sem held in read > + * mode. > */ > void cgroup_mm_owner_callbacks(struct task_struct *old, struct task_struct *new) > { > diff --git a/mm/memrlimitcgroup.c b/mm/memrlimitcgroup.c > index 8ee74f6..b3d20f5 100644 > --- a/mm/memrlimitcgroup.c > +++ b/mm/memrlimitcgroup.c > @@ -238,7 +238,7 @@ out: > } > > /* > - * This callback is called with mmap_sem held > + * This callback is called with mmap_sem and task_lock held > */ > static void memrlimit_cgroup_mm_owner_changed(struct cgroup_subsys *ss, > struct cgroup *old_cgrp, > @@ -246,9 +246,9 @@ static void memrlimit_cgroup_mm_owner_changed(struct cgroup_subsys *ss, > struct task_struct *p) > { > struct memrlimit_cgroup *memrcg, *old_memrcg; > - struct mm_struct *mm = get_task_mm(p); > + struct mm_struct *mm = p->mm; > > - BUG_ON(!mm); > + BUG_ON(!mm || (p->flags & PF_KTHREAD)); > > /* > * If we don't have a new cgroup, we just uncharge from the old one. > @@ -258,7 +258,7 @@ static void memrlimit_cgroup_mm_owner_changed(struct cgroup_subsys *ss, > memrcg = memrlimit_cgroup_from_cgrp(cgrp); > if (res_counter_charge(&memrcg->as_res, > mm->total_vm << PAGE_SHIFT)) > - goto out; > + return; > } > > if (old_cgrp) { > @@ -266,8 +266,6 @@ static void memrlimit_cgroup_mm_owner_changed(struct cgroup_subsys *ss, > res_counter_uncharge(&old_memrcg->as_res, > mm->total_vm << PAGE_SHIFT); > } > -out: > - mmput(mm); > }
Seems reasonable
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
-- Balbir
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