Re: [PATCH net-next v4 5/6] selftests: net: add multithread server support to iou-zcrx

[Juanlu Herrero <juanlu@fastmail.com>]

On Tue, Aug 04, 2026 at 12:42:41PM -0600, Paolo Abeni wrote:
> 
> 
> On 7/30/26 12:18 AM, Juanlu Herrero wrote:
> > Run the iou-zcrx server as N worker threads, each owning one receive
> > queue with its own io_uring and zero-copy receive (zcrx) ifq, so the
> > test can exercise multi-queue zero-copy receive.
> > 
> > The main thread owns the listening socket, accepts connections, and
> > dispatches each to the worker owning the queue it landed on by matching
> > SO_INCOMING_NAPI_ID against per-queue NAPI IDs.
> > 
> > Assisted-by: Claude:claude-opus-4-8
> > Signed-off-by: Juanlu Herrero <juanlu@fastmail.com>
> > ---
> >  .../testing/selftests/drivers/net/hw/Makefile |   5 +-
> >  .../selftests/drivers/net/hw/iou-zcrx.c       | 290 ++++++++++++++----
> >  2 files changed, 226 insertions(+), 69 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/drivers/net/hw/Makefile b/tools/testing/selftests/drivers/net/hw/Makefile
> > index 3cab3b4adbb2e..035581b58bc66 100644
> > --- a/tools/testing/selftests/drivers/net/hw/Makefile
> > +++ b/tools/testing/selftests/drivers/net/hw/Makefile
> > @@ -13,10 +13,6 @@ else
> >  $(warning excluding iouring tests, liburing not installed or too old)
> >  endif
> >  
> > -TEST_GEN_FILES := \
> > -	$(COND_GEN_FILES) \
> > -# end of TEST_GEN_FILES
> > -
> >  TEST_PROGS = \
> >  	csum.py \
> >  	devlink_port_split.py \
> > @@ -71,6 +67,7 @@ TEST_INCLUDES := \
> >  YNL_GEN_FILES := \
> >  	ncdevmem \
> >  	toeplitz \
> > +	$(COND_GEN_FILES) \
> >  # end of YNL_GEN_FILES
> >  TEST_GEN_FILES += $(YNL_GEN_FILES)
> >  TEST_GEN_FILES += $(patsubst %.c,%.o,$(wildcard *.bpf.c))
> > diff --git a/tools/testing/selftests/drivers/net/hw/iou-zcrx.c b/tools/testing/selftests/drivers/net/hw/iou-zcrx.c
> > index 7bc61f3b70ca6..16259129df46d 100644
> > --- a/tools/testing/selftests/drivers/net/hw/iou-zcrx.c
> > +++ b/tools/testing/selftests/drivers/net/hw/iou-zcrx.c
> > @@ -27,6 +27,7 @@
> >  #include <netinet/tcp.h>
> >  #include <netinet/udp.h>
> >  #include <sys/epoll.h>
> > +#include <sys/eventfd.h>
> >  #include <sys/ioctl.h>
> >  #include <sys/mman.h>
> >  #include <sys/resource.h>
> > @@ -38,6 +39,8 @@
> >  #include <sys/wait.h>
> >  
> >  #include <liburing.h>
> > +#include <ynl.h>
> > +#include "netdev-user.h"
> >  
> >  #define SKIP_CODE	42
> >  
> > @@ -91,6 +94,7 @@ static int cfg_num_threads = 1;
> >  static char *payload;
> >  
> >  #define CONNS_PER_THREAD	4
> > +#define MAX_CONNS_PER_THREAD	64
> >  
> >  struct thread_ctx {
> >  	struct io_uring		ring;
> > @@ -99,9 +103,14 @@ struct thread_ctx {
> >  	size_t			ring_size;
> >  	struct io_uring_zcrx_rq	rq_ring;
> >  	unsigned long		area_token;
> > -	int			connfd;
> > -	bool			stop;
> > -	size_t			received;
> > +	int			queue_id;
> > +	int			napi_id;
> > +	int			ready_fd;
> > +	int			start_fd;
> > +
> > +	int			connfds[MAX_CONNS_PER_THREAD];
> > +	size_t			received[MAX_CONNS_PER_THREAD];
> > +	int			nr_conns;
> >  };
> >  
> >  static unsigned long gettimeofday_ms(void)
> > @@ -201,7 +210,7 @@ static void setup_zcrx(struct thread_ctx *ctx)
> >  
> >  	struct t_io_uring_zcrx_ifq_reg reg = {
> >  		.if_idx = ifindex,
> > -		.if_rxq = cfg_queue_id,
> > +		.if_rxq = ctx->queue_id,
> >  		.rq_entries = rq_entries,
> >  		.area_ptr = (__u64)(unsigned long)&area_reg,
> >  		.region_ptr = (__u64)(unsigned long)&region_reg,
> > @@ -226,53 +235,32 @@ static void setup_zcrx(struct thread_ctx *ctx)
> >  	ctx->area_token = area_reg.rq_area_token;
> >  }
> >  
> > -static void add_accept(struct thread_ctx *ctx, int sockfd)
> > +static void add_recvzc(struct thread_ctx *ctx, int conn_idx)
> >  {
> >  	struct io_uring_sqe *sqe;
> >  
> >  	sqe = io_uring_get_sqe(&ctx->ring);
> >  
> > -	io_uring_prep_accept(sqe, sockfd, NULL, NULL, 0);
> > -	sqe->user_data = 1;
> > -}
> > -
> > -static void add_recvzc(struct thread_ctx *ctx, int sockfd)
> > -{
> > -	struct io_uring_sqe *sqe;
> > -
> > -	sqe = io_uring_get_sqe(&ctx->ring);
> > -
> > -	io_uring_prep_rw(IORING_OP_RECV_ZC, sqe, sockfd, NULL, 0, 0);
> > +	io_uring_prep_rw(IORING_OP_RECV_ZC, sqe, ctx->connfds[conn_idx],
> > +			 NULL, 0, 0);
> >  	sqe->ioprio |= IORING_RECV_MULTISHOT;
> > -	sqe->user_data = 2;
> > +	sqe->user_data = conn_idx;
> >  }
> >  
> > -static void add_recvzc_oneshot(struct thread_ctx *ctx, int sockfd, size_t len)
> > +static void add_recvzc_oneshot(struct thread_ctx *ctx, int conn_idx, size_t len)
> >  {
> >  	struct io_uring_sqe *sqe;
> >  
> >  	sqe = io_uring_get_sqe(&ctx->ring);
> >  
> > -	io_uring_prep_rw(IORING_OP_RECV_ZC, sqe, sockfd, NULL, len, 0);
> > +	io_uring_prep_rw(IORING_OP_RECV_ZC, sqe, ctx->connfds[conn_idx],
> > +			 NULL, len, 0);
> >  	sqe->ioprio |= IORING_RECV_MULTISHOT;
> > -	sqe->user_data = 2;
> > +	sqe->user_data = conn_idx;
> >  }
> >  
> > -static void process_accept(struct thread_ctx *ctx, struct io_uring_cqe *cqe)
> > -{
> > -	if (cqe->res < 0)
> > -		error(1, 0, "accept()");
> > -	if (ctx->connfd)
> > -		error(1, 0, "Unexpected second connection");
> > -
> > -	ctx->connfd = cqe->res;
> > -	if (cfg_oneshot)
> > -		add_recvzc_oneshot(ctx, ctx->connfd, page_size);
> > -	else
> > -		add_recvzc(ctx, ctx->connfd);
> > -}
> > -
> > -static void process_recvzc(struct thread_ctx *ctx, struct io_uring_cqe *cqe)
> > +static void process_recvzc(struct thread_ctx *ctx, struct io_uring_cqe *cqe,
> > +			   int conn_idx)
> >  {
> >  	unsigned int rq_mask = ctx->rq_ring.ring_entries - 1;
> >  	struct io_uring_zcrx_cqe *rcqe;
> > @@ -283,7 +271,7 @@ static void process_recvzc(struct thread_ctx *ctx, struct io_uring_cqe *cqe)
> >  	int i;
> >  
> >  	if (cqe->res == 0 && cqe->flags == 0 && cfg_oneshot_recvs == 0) {
> > -		ctx->stop = true;
> > +		ctx->nr_conns--;
> >  		return;
> >  	}
> >  
> > @@ -292,11 +280,11 @@ static void process_recvzc(struct thread_ctx *ctx, struct io_uring_cqe *cqe)
> >  
> >  	if (cfg_oneshot) {
> >  		if (cqe->res == 0 && cqe->flags == 0 && cfg_oneshot_recvs) {
> > -			add_recvzc_oneshot(ctx, ctx->connfd, page_size);
> > +			add_recvzc_oneshot(ctx, conn_idx, page_size);
> >  			cfg_oneshot_recvs--;
> 
> Sashiko noted that the above update is now racy in multithread tests:
> 
> https://sashiko.dev/#/patchset/20260729221825.42773-1-juanlu%40fastmail.com
> 
> Also please respect the reverse christmas tree order consistently.
> 
> /P
>

I will look into the potential race and fix the reverse christmas tree
ordering in v5. Thanks for the review

Best,
Juanlu