lkml.org 
[lkml]   [2011]   [Sep]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 1/4] cgroup: change locking order in attach_task_by_pid()
    Date
    From: Tejun Heo <tj@kernel.org>

    cgroup_mutex is updated to nest inside threadgroup_fork_lock instead
    of the other way around. threadgroup locking is scheduled to be
    updated to cover all threadgroup altering operations and nesting it
    inside cgroup_mutex complicates locking dependency unnecessarily.
    This also simplifies code a bit.

    The ugly "if (threadgroup)" conditionals for threadgroup locking will
    soon be removed.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Cc: Oleg Nesterov <oleg@redhat.com>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Paul Menage <menage@google.com>
    Cc: Li Zefan <lizf@cn.fujitsu.com>
    ---
    kernel/cgroup.c | 22 ++++++++++------------
    1 files changed, 10 insertions(+), 12 deletions(-)

    diff --git a/kernel/cgroup.c b/kernel/cgroup.c
    index 1d2b6ce..bd1fb5f 100644
    --- a/kernel/cgroup.c
    +++ b/kernel/cgroup.c
    @@ -2203,15 +2203,11 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
    const struct cred *cred = current_cred(), *tcred;
    int ret;

    - if (!cgroup_lock_live_group(cgrp))
    - return -ENODEV;
    -
    if (pid) {
    rcu_read_lock();
    tsk = find_task_by_vpid(pid);
    if (!tsk) {
    rcu_read_unlock();
    - cgroup_unlock();
    return -ESRCH;
    }
    if (threadgroup) {
    @@ -2225,7 +2221,6 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
    } else if (tsk->flags & PF_EXITING) {
    /* optimization for the single-task-only case */
    rcu_read_unlock();
    - cgroup_unlock();
    return -ESRCH;
    }

    @@ -2238,7 +2233,6 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
    cred->euid != tcred->uid &&
    cred->euid != tcred->suid) {
    rcu_read_unlock();
    - cgroup_unlock();
    return -EACCES;
    }
    get_task_struct(tsk);
    @@ -2251,15 +2245,19 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
    get_task_struct(tsk);
    }

    - if (threadgroup) {
    + if (threadgroup)
    threadgroup_fork_write_lock(tsk);
    - ret = cgroup_attach_proc(cgrp, tsk);
    - threadgroup_fork_write_unlock(tsk);
    - } else {
    - ret = cgroup_attach_task(cgrp, tsk);
    + ret = -ENODEV;
    + if (cgroup_lock_live_group(cgrp)) {
    + if (threadgroup)
    + ret = cgroup_attach_proc(cgrp, tsk);
    + else
    + ret = cgroup_attach_task(cgrp, tsk);
    + cgroup_unlock();
    }
    + if (threadgroup)
    + threadgroup_fork_write_unlock(tsk);
    put_task_struct(tsk);
    - cgroup_unlock();
    return ret;
    }

    --
    1.7.6


    \
     
     \ /
      Last update: 2011-09-04 20:05    [W:0.025 / U:0.032 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site