[PATCH 1/2] configfs: dir.c fix possible recursive locking - Kernel

This is a discussion on [PATCH 1/2] configfs: dir.c fix possible recursive locking - Kernel ; configfs_register_subsystem() with default_groups triggers recursive locking. it seems that mutex_lock_nested is needed. ============================================= [ INFO: possible recursive locking detected ] 2.6.24-rc6 #141 --------------------------------------------- swapper/1 is trying to acquire lock: (&sb->s_type->i_mutex_key#3){--..}, at: [ ] configfs_attach_group+0x4f/0x190 but task is already holding lock: ...

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Thread: [PATCH 1/2] configfs: dir.c fix possible recursive locking

  1. [PATCH 1/2] configfs: dir.c fix possible recursive locking

    configfs_register_subsystem() with default_groups triggers recursive locking.
    it seems that mutex_lock_nested is needed.

    =============================================
    [ INFO: possible recursive locking detected ]
    2.6.24-rc6 #141
    ---------------------------------------------
    swapper/1 is trying to acquire lock:
    (&sb->s_type->i_mutex_key#3){--..}, at: [] configfs_attach_group+0x4f/0x190

    but task is already holding lock:
    (&sb->s_type->i_mutex_key#3){--..}, at: [] configfs_register_subsystem+0x55/0x130

    other info that might help us debug this:
    1 lock held by swapper/1:
    #0: (&sb->s_type->i_mutex_key#3){--..}, at: [] configfs_register_subsystem+0x55/0x130

    stack backtrace:
    Pid: 1, comm: swapper Not tainted 2.6.24-rc6 #141
    [] show_trace_log_lvl+0x1a/0x30
    [] show_trace+0x12/0x20
    [] dump_stack+0x6e/0x80
    [] __lock_acquire+0xe62/0x1120
    [] lock_acquire+0x82/0xa0
    [] mutex_lock_nested+0x98/0x2e0
    [] configfs_attach_group+0x4f/0x190
    [] configfs_register_subsystem+0xc6/0x130
    [] init_netconsole+0x2b6/0x300
    [] kernel_init+0x142/0x320
    [] kernel_thread_helper+0x7/0x14
    =======================

    Signed-off-by: Joonwoo Park
    ---
    fs/configfs/dir.c | 5 +++--
    1 files changed, 3 insertions(+), 2 deletions(-)

    diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
    index 50ed691..a48dc7d 100644
    --- a/fs/configfs/dir.c
    +++ b/fs/configfs/dir.c
    @@ -546,7 +546,7 @@ static int populate_groups(struct config_group *group)
    * That said, taking our i_mutex is closer to mkdir
    * emulation, and shouldn't hurt.
    */
    - mutex_lock(&dentry->d_inode->i_mutex);
    + mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);

    for (i = 0; group->default_groups[i]; i++) {
    new_group = group->default_groups[i];
    @@ -1405,7 +1405,8 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
    sd = configfs_sb->s_root->d_fsdata;
    link_group(to_config_group(sd->s_element), group);

    - mutex_lock(&configfs_sb->s_root->d_inode->i_mutex);
    + mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
    + I_MUTEX_PARENT);

    name.name = group->cg_item.ci_name;
    name.len = strlen(name.name);
    ---

    Thanks.
    Joonwoo

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  2. Re: [PATCH 1/2] configfs: dir.c fix possible recursive locking

    On Wed, Dec 26, 2007 at 12:09:57PM +0900, Joonwoo Park wrote:
    > configfs_register_subsystem() with default_groups triggers recursive locking.
    > it seems that mutex_lock_nested is needed.


    Thanks for the work, I've added these to my tree.

    Joel

    > =============================================
    > [ INFO: possible recursive locking detected ]
    > 2.6.24-rc6 #141
    > ---------------------------------------------
    > swapper/1 is trying to acquire lock:
    > (&sb->s_type->i_mutex_key#3){--..}, at: [] configfs_attach_group+0x4f/0x190
    >
    > but task is already holding lock:
    > (&sb->s_type->i_mutex_key#3){--..}, at: [] configfs_register_subsystem+0x55/0x130
    >
    > other info that might help us debug this:
    > 1 lock held by swapper/1:
    > #0: (&sb->s_type->i_mutex_key#3){--..}, at: [] configfs_register_subsystem+0x55/0x130
    >
    > stack backtrace:
    > Pid: 1, comm: swapper Not tainted 2.6.24-rc6 #141
    > [] show_trace_log_lvl+0x1a/0x30
    > [] show_trace+0x12/0x20
    > [] dump_stack+0x6e/0x80
    > [] __lock_acquire+0xe62/0x1120
    > [] lock_acquire+0x82/0xa0
    > [] mutex_lock_nested+0x98/0x2e0
    > [] configfs_attach_group+0x4f/0x190
    > [] configfs_register_subsystem+0xc6/0x130
    > [] init_netconsole+0x2b6/0x300
    > [] kernel_init+0x142/0x320
    > [] kernel_thread_helper+0x7/0x14
    > =======================
    >
    > Signed-off-by: Joonwoo Park
    > ---
    > fs/configfs/dir.c | 5 +++--
    > 1 files changed, 3 insertions(+), 2 deletions(-)
    >
    > diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
    > index 50ed691..a48dc7d 100644
    > --- a/fs/configfs/dir.c
    > +++ b/fs/configfs/dir.c
    > @@ -546,7 +546,7 @@ static int populate_groups(struct config_group *group)
    > * That said, taking our i_mutex is closer to mkdir
    > * emulation, and shouldn't hurt.
    > */
    > - mutex_lock(&dentry->d_inode->i_mutex);
    > + mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
    >
    > for (i = 0; group->default_groups[i]; i++) {
    > new_group = group->default_groups[i];
    > @@ -1405,7 +1405,8 @@ int configfs_register_subsystem(struct configfs_subsystem *subsys)
    > sd = configfs_sb->s_root->d_fsdata;
    > link_group(to_config_group(sd->s_element), group);
    >
    > - mutex_lock(&configfs_sb->s_root->d_inode->i_mutex);
    > + mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
    > + I_MUTEX_PARENT);
    >
    > name.name = group->cg_item.ci_name;
    > name.len = strlen(name.name);
    > ---
    >
    > Thanks.
    > Joonwoo
    >


    --

    "One of the symptoms of an approaching nervous breakdown is the
    belief that one's work is terribly important."
    - Bertrand Russell

    Joel Becker
    Principal Software Developer
    Oracle
    E-mail: joel.becker@oracle.com
    Phone: (650) 506-8127
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