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    SubjectRe: [PATCH] async: Let kfree() out of the critical area of the lock
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    On 2019/9/25 23:20, Alexander Duyck wrote:
    > On Wed, 2019-09-25 at 20:52 +0800, Yunfeng Ye wrote:
    >> It's not necessary to put kfree() in the critical area of the lock, so
    >> let it out.
    >>
    >> Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
    >> ---
    >> 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);
    >> }
    >
    > It probably wouldn't hurt to update the patch description to mention that
    > async_schedule_node_domain does the allocation outside of the lock, then
    > takes the lock and does the list addition and entry_count increment inside
    > the critical section so this is just updating the code to match that it
    > seems.
    >
    > Otherwise the change itself looks safe to me, though I am not sure there
    > is a performance gain to be had so this is mostly just a cosmetic patch.
    >
    The async_lock is big global lock, I think it's good to put kfree() outside
    to keep the critical area as short as possible.

    thanks.

    > Reviewed-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
    >
    >
    > .
    >

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