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    Subject[tip:smp/hotplug] padata: Avoid nested calls to get_online_cpus() in pcrypt_init_padata()
    Commit-ID:  bbd8797975ce0191ac72d575f7e34033b5a5f620
    Gitweb: http://git.kernel.org/tip/bbd8797975ce0191ac72d575f7e34033b5a5f620
    Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    AuthorDate: Tue, 18 Apr 2017 19:04:46 +0200
    Committer: Thomas Gleixner <tglx@linutronix.de>
    CommitDate: Thu, 20 Apr 2017 13:08:51 +0200

    padata: Avoid nested calls to get_online_cpus() in pcrypt_init_padata()

    pcrypt_init_padata()
    get_online_cpus()
    padata_alloc_possible()
    padata_alloc()
    get_online_cpus()

    The nested call to get_online_cpus() works with the current implementation,
    but prevents the conversion to a percpu rwsem.

    The other caller of padata_alloc_possible() is pcrypt_init_padata() which
    calls from a get_online_cpus() protected region as well.

    Remove the get_online_cpus() call in padata_alloc() and document the
    calling convention.

    Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Cc: Steffen Klassert <steffen.klassert@secunet.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    Cc: linux-crypto@vger.kernel.org
    Link: http://lkml.kernel.org/r/20170418170552.697398655@linutronix.de

    ---
    kernel/padata.c | 6 ++++--
    1 file changed, 4 insertions(+), 2 deletions(-)

    diff --git a/kernel/padata.c b/kernel/padata.c
    index 18992bf..e5ff511 100644
    --- a/kernel/padata.c
    +++ b/kernel/padata.c
    @@ -945,6 +945,8 @@ static struct kobj_type padata_attr_type = {
    * @wq: workqueue to use for the allocated padata instance
    * @pcpumask: cpumask that will be used for padata parallelization
    * @cbcpumask: cpumask that will be used for padata serialization
    + *
    + * Must be called from a get_online_cpus() protected region
    */
    static struct padata_instance *padata_alloc(struct workqueue_struct *wq,
    const struct cpumask *pcpumask,
    @@ -957,7 +959,6 @@ static struct padata_instance *padata_alloc(struct workqueue_struct *wq,
    if (!pinst)
    goto err;

    - get_online_cpus();
    if (!alloc_cpumask_var(&pinst->cpumask.pcpu, GFP_KERNEL))
    goto err_free_inst;
    if (!alloc_cpumask_var(&pinst->cpumask.cbcpu, GFP_KERNEL)) {
    @@ -997,7 +998,6 @@ err_free_masks:
    free_cpumask_var(pinst->cpumask.cbcpu);
    err_free_inst:
    kfree(pinst);
    - put_online_cpus();
    err:
    return NULL;
    }
    @@ -1008,6 +1008,8 @@ err:
    * parallel workers.
    *
    * @wq: workqueue to use for the allocated padata instance
    + *
    + * Must be called from a get_online_cpus() protected region
    */
    struct padata_instance *padata_alloc_possible(struct workqueue_struct *wq)
    {
    \
     
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      Last update: 2017-04-20 13:23    [W:3.098 / U:0.124 seconds]
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