On 4/23/22 2:06 AM, Pavel Begunkov wrote:
> On 4/22/22 22:42, Jens Axboe wrote:
>> Rather than require ctx->completion_lock for ensuring that we don't
>> clobber the flags, use try_cmpxchg() instead. This removes the need
>> to grab the completion_lock, in preparation for needing to set or
>> clear sq_flags when we don't know the status of this lock.
>>
>> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
>> ---
>> fs/io_uring.c | 54 ++++++++++++++++++++++++++++++---------------------
>> 1 file changed, 32 insertions(+), 22 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index 626bf840bed2..38e58fe4963d 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -1999,6 +1999,34 @@ static void io_cqring_ev_posted_iopoll(struct io_ring_ctx *ctx)
>> io_cqring_wake(ctx);
>> }
>> +static void io_ring_sq_flag_clear(struct io_ring_ctx *ctx, unsigned int flag)
>> +{
>> + struct io_rings *rings = ctx->rings;
>> + unsigned int oldf, newf;
>> +
>> + do {
>> + oldf = READ_ONCE(rings->sq_flags);
>> +
>> + if (!(oldf & flag))
>> + break;
>> + newf = oldf & ~flag;
>> + } while (!try_cmpxchg(&rings->sq_flags, &oldf, newf));
>> +}
>> +
>> +static void io_ring_sq_flag_set(struct io_ring_ctx *ctx, unsigned int flag)
>> +{
>> + struct io_rings *rings = ctx->rings;
>> + unsigned int oldf, newf;
>> +
>> + do {
>> + oldf = READ_ONCE(rings->sq_flags);
>> +
>> + if (oldf & flag)
>> + break;
>> + newf = oldf | flag;
>> + } while (!try_cmpxchg(&rings->sq_flags, &oldf, newf));
>> +}
>
> atomic and/or might be a better fit
That would indeed be great, but the type is fixed. Not sure if all archs
end up with a plain int as the type?
--
Jens Axboe
