Re: [PATCH 1/7] mmu_notifier: add call_srcu and sync function for listener to delay call and sync.

[Oded Gabbay <oded.gabbay@amd.com>]

On 21/07/14 18:01, Oded Gabbay wrote:
> On 17/07/14 21:46, j.glisse@gmail.com wrote:
>> From: Peter Zijlstra <peterz@infradead.org>
>>
>> New mmu_notifier listener are eager to cleanup there structure after the
>> mmu_notifier::release callback. In order to allow this the patch provide
>> a function that allows to add a delayed call to the mmu_notifier srcu. It
>> also add a function that will call barrier_srcu so those listener can sync
>> with mmu_notifier.
>
> Tested with amdkfd and iommuv2 driver
> So,
> Tested-by: Oded Gabbay <oded.gabbay@amd.com>

akpm, any chance that only this specific patch from Peter.Z will get in 3.17 ?
I must have it for amdkfd (HSA driver). Without it, I can't be in 3.17 either.

	Oded

>>
>> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
>> Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
>> ---
>>   include/linux/mmu_notifier.h |  6 ++++++
>>   mm/mmu_notifier.c            | 40 +++++++++++++++++++++++++++++++++++++++-
>>   2 files changed, 45 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
>> index deca874..2728869 100644
>> --- a/include/linux/mmu_notifier.h
>> +++ b/include/linux/mmu_notifier.h
>> @@ -170,6 +170,8 @@ extern int __mmu_notifier_register(struct mmu_notifier *mn,
>>                      struct mm_struct *mm);
>>   extern void mmu_notifier_unregister(struct mmu_notifier *mn,
>>                       struct mm_struct *mm);
>> +extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
>> +                           struct mm_struct *mm);
>>   extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
>>   extern void __mmu_notifier_release(struct mm_struct *mm);
>>   extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
>> @@ -288,6 +290,10 @@ static inline void mmu_notifier_mm_destroy(struct
>> mm_struct *mm)
>>       set_pte_at(___mm, ___address, __ptep, ___pte);            \
>>   })
>>
>> +extern void mmu_notifier_call_srcu(struct rcu_head *rcu,
>> +                   void (*func)(struct rcu_head *rcu));
>> +extern void mmu_notifier_synchronize(void);
>> +
>>   #else /* CONFIG_MMU_NOTIFIER */
>>
>>   static inline void mmu_notifier_release(struct mm_struct *mm)
>> diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
>> index 41cefdf..950813b 100644
>> --- a/mm/mmu_notifier.c
>> +++ b/mm/mmu_notifier.c
>> @@ -23,6 +23,25 @@
>>   static struct srcu_struct srcu;
>>
>>   /*
>> + * This function allows mmu_notifier::release callback to delay a call to
>> + * a function that will free appropriate resources. The function must be
>> + * quick and must not block.
>> + */
>> +void mmu_notifier_call_srcu(struct rcu_head *rcu,
>> +                void (*func)(struct rcu_head *rcu))
>> +{
>> +    call_srcu(&srcu, rcu, func);
>> +}
>> +EXPORT_SYMBOL_GPL(mmu_notifier_call_srcu);
>> +
>> +void mmu_notifier_synchronize(void)
>> +{
>> +    /* Wait for any running method to finish. */
>> +    srcu_barrier(&srcu);
>> +}
>> +EXPORT_SYMBOL_GPL(mmu_notifier_synchronize);
>> +
>> +/*
>>    * This function can't run concurrently against mmu_notifier_register
>>    * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
>>    * runs with mm_users == 0. Other tasks may still invoke mmu notifiers
>> @@ -53,7 +72,6 @@ void __mmu_notifier_release(struct mm_struct *mm)
>>            */
>>           if (mn->ops->release)
>>               mn->ops->release(mn, mm);
>> -    srcu_read_unlock(&srcu, id);
>>
>>       spin_lock(&mm->mmu_notifier_mm->lock);
>>       while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
>> @@ -69,6 +87,7 @@ void __mmu_notifier_release(struct mm_struct *mm)
>>           hlist_del_init_rcu(&mn->hlist);
>>       }
>>       spin_unlock(&mm->mmu_notifier_mm->lock);
>> +    srcu_read_unlock(&srcu, id);
>>
>>       /*
>>        * synchronize_srcu here prevents mmu_notifier_release from returning to
>> @@ -325,6 +344,25 @@ void mmu_notifier_unregister(struct mmu_notifier *mn,
>> struct mm_struct *mm)
>>   }
>>   EXPORT_SYMBOL_GPL(mmu_notifier_unregister);
>>
>> +/*
>> + * Same as mmu_notifier_unregister but no callback and no srcu synchronization.
>> + */
>> +void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
>> +                    struct mm_struct *mm)
>> +{
>> +    spin_lock(&mm->mmu_notifier_mm->lock);
>> +    /*
>> +     * Can not use list_del_rcu() since __mmu_notifier_release
>> +     * can delete it before we hold the lock.
>> +     */
>> +    hlist_del_init_rcu(&mn->hlist);
>> +    spin_unlock(&mm->mmu_notifier_mm->lock);
>> +
>> +    BUG_ON(atomic_read(&mm->mm_count) <= 0);
>> +    mmdrop(mm);
>> +}
>> +EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release);
>> +
>>   static int __init mmu_notifier_init(void)
>>   {
>>       return init_srcu_struct(&srcu);
>>
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org.  For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=ilto:"dont@kvack.org"> email@kvack.org </a>

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>