Re: [PATCH v2] async: Let kfree() out of the critical area of the lock

From: Yunfeng Ye
Date: Mon Nov 18 2019 - 22:01:51 EST




On 2019/11/16 2:32, Thomas Gleixner wrote:
>
>
> On Fri, 11 Oct 2019, Yunfeng Ye wrote:
>
>> The async_lock is big global lock, and kfree() is not always cheap, it
>> will increase lock contention. it's better let kfree() outside the lock
>> to keep the critical area as short as possible.
>>
>> Signed-off-by: Yunfeng Ye <yeyunfeng@xxxxxxxxxx>
>> Reviewed-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
>> Reviewed-by: Bart Van Assche <bvanassche@xxxxxxx>
>> ---
>> v1 -> v2:
>> - update the description
>> - add "Reviewed-by"
>>
>> kernel/async.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/async.c b/kernel/async.c
>> index 4f9c1d6..1de270d 100644
>> --- a/kernel/async.c
>> +++ b/kernel/async.c
>> @@ -135,12 +135,12 @@ static void async_run_entry_fn(struct work_struct *work)
>> list_del_init(&entry->domain_list);
>> list_del_init(&entry->global_list);
>>
>> - /* 3) free the entry */
>> - kfree(entry);
>> atomic_dec(&entry_count);
>> -
>> spin_unlock_irqrestore(&async_lock, flags);
>>
>> + /* 3) free the entry */
>> + kfree(entry);
>> +
>> /* 4) wake up any waiters */
>> wake_up(&async_done);
>
> The wakeup should happen before the kfree() for the very same reasons.
>
ok, I will modify as your suggest, thanks.

> Thanks,
>
> tglx
>
> .
>