lkml.org 
[lkml]   [2009]   [Jun]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH 2/2] cgroup: exlclude release rmdir
    From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

    Paul Menage pointed out that css_get()/put() only for avoiding race with
    rmdir() is complicated and these should be treated as it is for.

    This adds
    - cgroup_exclude_rmdir() ....prevent rmdir() for a while.
    - cgroup_release_rmdir() ....rerun rmdir() if necessary.
    And hides cgroup_wakeup_rmdir_waiter() into kernel/cgroup.c, again.

    Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

    ---
    include/linux/cgroup.h | 21 +++++++++++----------
    kernel/cgroup.c | 17 +++++++++++++++--
    mm/memcontrol.c | 12 ++++--------
    3 files changed, 30 insertions(+), 20 deletions(-)

    Index: mmotm-2.6.31-Jun25/include/linux/cgroup.h
    ===================================================================
    --- mmotm-2.6.31-Jun25.orig/include/linux/cgroup.h
    +++ mmotm-2.6.31-Jun25/include/linux/cgroup.h
    @@ -366,17 +366,18 @@ int cgroup_task_count(const struct cgrou
    int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task);

    /*
    - * Allow to use CGRP_WAIT_ON_RMDIR flag to check race with rmdir() for subsys.
    - * Subsys can call this function if it's necessary to call pre_destroy() again
    - * because it adds not-temporary refs to css after or while pre_destroy().
    - * The caller of this function should use css_tryget(), too.
    + * When the subsys has to access css and may add permanent refcnt to css,
    + * it should take care of racy conditions with rmdir(). Following set of
    + * functions, is for stop/restart rmdir if necessary.
    + * Because these will call css_get/put, "css" should be alive css.
    + *
    + * cgroup_exclude_rmdir();
    + * ...do some jobs which may access arbitrary empty cgroup
    + * cgroup_release_rmdir();
    */
    -void __cgroup_wakeup_rmdir_waiters(void);
    -static inline void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
    -{
    - if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
    - __cgroup_wakeup_rmdir_waiters();
    -}
    +
    +void cgroup_exclude_rmdir(struct cgroup_subsys_state *css);
    +void cgroup_release_rmdir(struct cgroup_subsys_state *css);

    /*
    * Control Group subsystem type.
    Index: mmotm-2.6.31-Jun25/kernel/cgroup.c
    ===================================================================
    --- mmotm-2.6.31-Jun25.orig/kernel/cgroup.c
    +++ mmotm-2.6.31-Jun25/kernel/cgroup.c
    @@ -738,11 +738,24 @@ static void cgroup_d_remove_dir(struct d
    */
    DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);

    -void __cgroup_wakeup_rmdir_waiters(void)
    +static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
    {
    - wake_up_all(&cgroup_rmdir_waitq);
    + if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
    + wake_up_all(&cgroup_rmdir_waitq);
    }

    +void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
    +{
    + css_get(css);
    +}
    +
    +void cgroup_release_rmdir(struct cgroup_subsys_state *css)
    +{
    + cgroup_wakeup_rmdir_waiter(css->cgroup);
    + css_put(css);
    +}
    +
    +
    static int rebind_subsystems(struct cgroupfs_root *root,
    unsigned long final_bits)
    {
    Index: mmotm-2.6.31-Jun25/mm/memcontrol.c
    ===================================================================
    --- mmotm-2.6.31-Jun25.orig/mm/memcontrol.c
    +++ mmotm-2.6.31-Jun25/mm/memcontrol.c
    @@ -1461,7 +1461,7 @@ __mem_cgroup_commit_charge_swapin(struct
    return;
    if (!ptr)
    return;
    - css_get(&ptr->css);
    + cgroup_exclude_rmdir(&ptr->css);
    pc = lookup_page_cgroup(page);
    mem_cgroup_lru_del_before_commit_swapcache(page);
    __mem_cgroup_commit_charge(ptr, pc, ctype);
    @@ -1496,9 +1496,7 @@ __mem_cgroup_commit_charge_swapin(struct
    * So, rmdir()->pre_destroy() can be called while we do this charge.
    * In that case, we need to call pre_destroy() again. check it here.
    */
    - cgroup_wakeup_rmdir_waiter(ptr->css.cgroup);
    - css_put(&ptr->css);
    -
    + cgroup_release_rmdir(&ptr->css);
    }

    void mem_cgroup_commit_charge_swapin(struct page *page, struct mem_cgroup *ptr)
    @@ -1704,7 +1702,7 @@ void mem_cgroup_end_migration(struct mem

    if (!mem)
    return;
    - css_get(&mem->css);
    + cgroup_exclude_rmdir(&mem->css);
    /* at migration success, oldpage->mapping is NULL. */
    if (oldpage->mapping) {
    target = oldpage;
    @@ -1749,9 +1747,7 @@ void mem_cgroup_end_migration(struct mem
    * So, rmdir()->pre_destroy() can be called while we do this charge.
    * In that case, we need to call pre_destroy() again. check it here.
    */
    - cgroup_wakeup_rmdir_waiter(mem->css.cgroup);
    - css_put(&mem->css);
    -
    + cgroup_release_rmdir(&mem->css);
    }

    /*


    \
     
     \ /
      Last update: 2009-06-30 11:09    [W:0.035 / U:209.632 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site