lkml.org 
[lkml]   [2019]   [Dec]   [13]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [PATCH 1/1] io_uring: don't wait when under-submitting
From
Date
On 12/13/19 12:51 AM, Pavel Begunkov wrote:
> There is no reliable way to submit and wait in a single syscall, as
> io_submit_sqes() may under-consume sqes (in case of an early error).
> Then it will wait for not-yet-submitted requests, deadlocking the user
> in most cases.

Why not just cap the wait_nr? If someone does to_submit = 8, wait_nr = 8,
and we only submit 4, just wait for 4? Ala:

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 81219a631a6d..4a76ccbb7856 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -5272,6 +5272,10 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
submitted = io_submit_sqes(ctx, to_submit, f.file, fd,
&cur_mm, false);
mutex_unlock(&ctx->uring_lock);
+ if (submitted <= 0)
+ goto done;
+ if (submitted != to_submit && min_complete > submitted)
+ min_complete = submitted;
}
if (flags & IORING_ENTER_GETEVENTS) {
unsigned nr_events = 0;
@@ -5284,7 +5288,7 @@ SYSCALL_DEFINE6(io_uring_enter, unsigned int, fd, u32, to_submit,
ret = io_cqring_wait(ctx, min_complete, sig, sigsz);
}
}
-
+done:
percpu_ref_put(&ctx->refs);
out_fput:
fdput(f);
--
Jens Axboe

\
 
 \ /
  Last update: 2019-12-13 19:23    [W:0.069 / U:0.308 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site