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    Subject[PATCH 4.7 057/184] IB/hfi1,IB/qib: Fix qp_stats sleep with rcu read lock held
    Date
    4.7-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Mike Marciniszyn <mike.marciniszyn@intel.com>

    commit c62fb260a86dde3df5b2905432caa0e9f6898434 upstream.

    The qp init function does a kzalloc() while holding the RCU
    lock that encounters the following warning with a debug kernel
    when a cat of the qp_stats is done:

    [ 231.723948] rcu_scheduler_active = 1, debug_locks = 0
    [ 231.731939] 3 locks held by cat/11355:
    [ 231.736492] #0: (debugfs_srcu){......}, at: [<ffffffff813001a5>] debugfs_use_file_start+0x5/0x90
    [ 231.746955] #1: (&p->lock){+.+.+.}, at: [<ffffffff81289a6c>] seq_read+0x4c/0x3c0
    [ 231.755873] #2: (rcu_read_lock){......}, at: [<ffffffffa0a0c535>] _qp_stats_seq_start+0x5/0xd0 [hfi1]
    [ 231.766862]

    The init functions do an implicit next which requires the rcu read lock
    before the kzalloc().

    Fix for both drivers is to change the scope of the init function to only
    do the allocation and the initialization of the just allocated iter.

    The implict next is moved back into the respective start functions to fix
    the issue.

    Signed-off-by: Ira Weiny <ira.weiny@intel.com>
    Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
    Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
    Signed-off-by: Doug Ledford <dledford@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/infiniband/hw/hfi1/debugfs.c | 14 +++++++++-----
    drivers/infiniband/hw/hfi1/qp.c | 4 ----
    drivers/infiniband/hw/qib/qib_debugfs.c | 12 +++++++++---
    drivers/infiniband/hw/qib/qib_qp.c | 4 ----
    4 files changed, 18 insertions(+), 16 deletions(-)

    --- a/drivers/infiniband/hw/hfi1/debugfs.c
    +++ b/drivers/infiniband/hw/hfi1/debugfs.c
    @@ -223,28 +223,32 @@ DEBUGFS_SEQ_FILE_OPEN(ctx_stats)
    DEBUGFS_FILE_OPS(ctx_stats);

    static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
    -__acquires(RCU)
    + __acquires(RCU)
    {
    struct qp_iter *iter;
    loff_t n = *pos;

    - rcu_read_lock();
    iter = qp_iter_init(s->private);
    +
    + /* stop calls rcu_read_unlock */
    + rcu_read_lock();
    +
    if (!iter)
    return NULL;

    - while (n--) {
    + do {
    if (qp_iter_next(iter)) {
    kfree(iter);
    return NULL;
    }
    - }
    + } while (n--);

    return iter;
    }

    static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
    loff_t *pos)
    + __must_hold(RCU)
    {
    struct qp_iter *iter = iter_ptr;

    @@ -259,7 +263,7 @@ static void *_qp_stats_seq_next(struct s
    }

    static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
    -__releases(RCU)
    + __releases(RCU)
    {
    rcu_read_unlock();
    }
    --- a/drivers/infiniband/hw/hfi1/qp.c
    +++ b/drivers/infiniband/hw/hfi1/qp.c
    @@ -595,10 +595,6 @@ struct qp_iter *qp_iter_init(struct hfi1

    iter->dev = dev;
    iter->specials = dev->rdi.ibdev.phys_port_cnt * 2;
    - if (qp_iter_next(iter)) {
    - kfree(iter);
    - return NULL;
    - }

    return iter;
    }
    --- a/drivers/infiniband/hw/qib/qib_debugfs.c
    +++ b/drivers/infiniband/hw/qib/qib_debugfs.c
    @@ -189,27 +189,32 @@ static int _ctx_stats_seq_show(struct se
    DEBUGFS_FILE(ctx_stats)

    static void *_qp_stats_seq_start(struct seq_file *s, loff_t *pos)
    + __acquires(RCU)
    {
    struct qib_qp_iter *iter;
    loff_t n = *pos;

    - rcu_read_lock();
    iter = qib_qp_iter_init(s->private);
    +
    + /* stop calls rcu_read_unlock */
    + rcu_read_lock();
    +
    if (!iter)
    return NULL;

    - while (n--) {
    + do {
    if (qib_qp_iter_next(iter)) {
    kfree(iter);
    return NULL;
    }
    - }
    + } while (n--);

    return iter;
    }

    static void *_qp_stats_seq_next(struct seq_file *s, void *iter_ptr,
    loff_t *pos)
    + __must_hold(RCU)
    {
    struct qib_qp_iter *iter = iter_ptr;

    @@ -224,6 +229,7 @@ static void *_qp_stats_seq_next(struct s
    }

    static void _qp_stats_seq_stop(struct seq_file *s, void *iter_ptr)
    + __releases(RCU)
    {
    rcu_read_unlock();
    }
    --- a/drivers/infiniband/hw/qib/qib_qp.c
    +++ b/drivers/infiniband/hw/qib/qib_qp.c
    @@ -530,10 +530,6 @@ struct qib_qp_iter *qib_qp_iter_init(str
    return NULL;

    iter->dev = dev;
    - if (qib_qp_iter_next(iter)) {
    - kfree(iter);
    - return NULL;
    - }

    return iter;
    }

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