-----"Steve Wise" <larrystevenwise@xxxxxxxxx> wrote: -----
>To: "Bernard Metzler" <bmt@xxxxxxxxxxxxxx>
>From: "Steve Wise" <larrystevenwise@xxxxxxxxx>
>Date: 09/07/2019 12:31AM
>Cc: linux-rdma@xxxxxxxxxxxxxxx, dledford@xxxxxxxxxx
>Subject: [EXTERNAL] Re: [PATCH] RDMA/siw: Relax from kmap_atomic()
>use in TX path
>
>Hey Bernard, is the code below called directly from the driver’s
>post_send function? If so it must use atomic...I think.
>
Hey Steve,
Only a kernel TX thread executes the TX path. It is not
executed directly from the drivers post_send() method,
which only queues work for TX processing and wakes up
the TX thread if it currently does not run.
The single exception is TX processing
out of a user space application context, if no TX
thread is currently running, but only for a small
burst. In any case, all TX processing is done out of
a non-atomic context.
Best,
Bernard.
>Stevo
>
>> On Sep 6, 2019, at 6:18 AM, Bernard Metzler <bmt@xxxxxxxxxxxxxx>
>wrote:
>>
>> Since the transmit path is never executed in an atomic
>> context, we do not need kmap_atomic() and can always
>> use less demanding kmap().
>>
>> Signed-off-by: Bernard Metzler <bmt@xxxxxxxxxxxxxx>
>> ---
>> drivers/infiniband/sw/siw/siw_qp_tx.c | 12 +++++-------
>> 1 file changed, 5 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/infiniband/sw/siw/siw_qp_tx.c
>b/drivers/infiniband/sw/siw/siw_qp_tx.c
>> index 8e72f955921d..5d97bba0ce6d 100644
>> --- a/drivers/infiniband/sw/siw/siw_qp_tx.c
>> +++ b/drivers/infiniband/sw/siw/siw_qp_tx.c
>> @@ -76,16 +76,15 @@ static int siw_try_1seg(struct siw_iwarp_tx
>*c_tx, void *paddr)
>> if (unlikely(!p))
>> return -EFAULT;
>>
>> - buffer = kmap_atomic(p);
>> + buffer = kmap(p);
>>
>> if (likely(PAGE_SIZE - off >= bytes)) {
>> memcpy(paddr, buffer + off, bytes);
>> - kunmap_atomic(buffer);
>> } else {
>> unsigned long part = bytes - (PAGE_SIZE - off);
>>
>> memcpy(paddr, buffer + off, part);
>> - kunmap_atomic(buffer);
>> + kunmap(p);
>>
>> if (!mem->is_pbl)
>> p = siw_get_upage(mem->umem,
>> @@ -97,11 +96,10 @@ static int siw_try_1seg(struct siw_iwarp_tx
>*c_tx, void *paddr)
>> if (unlikely(!p))
>> return -EFAULT;
>>
>> - buffer = kmap_atomic(p);
>> - memcpy(paddr + part, buffer,
>> - bytes - part);
>> - kunmap_atomic(buffer);
>> + buffer = kmap(p);
>> + memcpy(paddr + part, buffer, bytes - part);
>> }
>> + kunmap(p);
>> }
>> }
>> return (int)bytes;
>> --
>> 2.17.2
>>
>
>
