io_uring: retry io_uring_submit() if it fails with errno=EINTR

Commit Message

Stefano Garzarella May 19, 2020, 1:30 p.m. UTC

As recently documented [1], io_uring_enter(2) syscall can return an
error (errno=EINTR) if the operation was interrupted by a delivery
of a signal before it could complete.

This should happen when IORING_ENTER_GETEVENTS flag is used, for
example during io_uring_submit_and_wait() or during io_uring_submit()
when IORING_SETUP_IOPOLL is enabled.

We shouldn't have this problem for now, but it's better to prevent it.

[1] https://github.com/axboe/liburing/commit/344355ec6619de8f4e64584c9736530b5346e4f4

Signed-off-by: Stefano Garzarella <[e-mail]>
---
 block/io_uring.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Stefan Hajnoczi May 21, 2020, 2:40 p.m. UTC | #1

On Tue, May 19, 2020 at 03:30:41PM +0200, Stefano Garzarella wrote:
> As recently documented [1], io_uring_enter(2) syscall can return an
> error (errno=EINTR) if the operation was interrupted by a delivery
> of a signal before it could complete.
> 
> This should happen when IORING_ENTER_GETEVENTS flag is used, for
> example during io_uring_submit_and_wait() or during io_uring_submit()
> when IORING_SETUP_IOPOLL is enabled.
> 
> We shouldn't have this problem for now, but it's better to prevent it.
> 
> [1] https://github.com/axboe/liburing/commit/344355ec6619de8f4e64584c9736530b5346e4f4
> 
> Signed-off-by: Stefano Garzarella <[e-mail]>
> ---
>  block/io_uring.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan

Patch

diff --git a/block/io_uring.c b/block/io_uring.c
index a3142ca989..9765681f7c 100644
--- a/block/io_uring.c
+++ b/block/io_uring.c
@@ -231,7 +231,7 @@  static int ioq_submit(LuringState *s)
         trace_luring_io_uring_submit(s, ret);
         /* Prevent infinite loop if submission is refused */
         if (ret <= 0) {
-            if (ret == -EAGAIN) {
+            if (ret == -EAGAIN || ret == -EINTR) {
                 continue;
             }
             break;