linux-kernel - Re: io_uring: process task work in io_uring

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Date:   Thu, 8 Oct 2020 19:09:41 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Colin Ian King <colin.king@...onical.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        io-uring@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: io_uring: process task work in io_uring_register()

On 10/8/20 12:23 PM, Colin Ian King wrote:
> Hi,
> 
> Static analysis with Coverity has detected a "dead-code" issue with the
> following commit:
> 
> commit af9c1a44f8dee7a958e07977f24ba40e3c770987
> Author: Jens Axboe <axboe@...nel.dk>
> Date:   Thu Sep 24 13:32:18 2020 -0600
> 
>     io_uring: process task work in io_uring_register()
> 
> The analysis is as follows:
> 
> 9513                do {
> 9514                        ret =
> wait_for_completion_interruptible(&ctx->ref_comp);
> 
> cond_const: Condition ret, taking false branch. Now the value of ret is
> equal to 0.
> 
> 9515                        if (!ret)
> 9516                                break;
> 9517                        if (io_run_task_work_sig() > 0)
> 9518                                continue;
> 9519                } while (1);
> 9520
> 9521                mutex_lock(&ctx->uring_lock);
> 9522
> 
> const: At condition ret, the value of ret must be equal to 0.
> dead_error_condition: The condition ret cannot be true.

Thanks, yeah that condition is reversed, should be:


diff --git a/fs/io_uring.c b/fs/io_uring.c
index 4df5b14c2e56..80a0aa33db49 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -9511,8 +9511,8 @@ static int __io_uring_register(struct io_ring_ctx *ctx, unsigned opcode,
 			ret = wait_for_completion_interruptible(&ctx->ref_comp);
 			if (!ret)
 				break;
-			if (io_run_task_work_sig() > 0)
-				continue;
+			if (io_run_task_work_sig() <= 0)
+				break;
 		} while (1);
 
 		mutex_lock(&ctx->uring_lock);

-- 
Jens Axboe