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

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Message-ID: <CAG48ez0pLGtc6_NPcYa0nVPexrSOJvfKgArgY6OT4AXS5tOF4A@mail.gmail.com>
Date:   Thu, 8 Oct 2020 21:14:42 +0200
From:   Jann Horn <jannh@...gle.com>
To:     Colin Ian King <colin.king@...onical.com>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        io-uring <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 Thu, Oct 8, 2020 at 9:13 PM Jann Horn <jannh@...gle.com> wrote:
>
> On Thu, Oct 8, 2020 at 8:24 PM Colin Ian King <colin.king@...onical.com> wrote:
> > 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.
>
> Does this mean Coverity is claiming that
> wait_for_completion_interruptible() can't return non-zero values? If
> so, can you figure out why Coverity thinks that? If that was true,
> it'd sound like a core kernel bug, rather than a uring issue...

Ah, nevermind, I missed the part where we only break out of the loop
if ret==0... sorry for the noise, ignore me.