linux-kernel - Re: [PATCH 2/4] uml: helper.c warning corrections

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Date:	Tue, 5 Jul 2011 14:02:50 +0200
From:	Richard Weinberger <richard@....at>
To:	Vitaliy Ivanov <vitalivanov@...il.com>
Cc:	Jeff Dike <jdike@...toit.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"user-mode-linux-devel@...ts.sourceforge.net" 
	<user-mode-linux-devel@...ts.sourceforge.net>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] uml: helper.c warning corrections

Am Dienstag 05 Juli 2011, 13:45:06 schrieb Vitaliy Ivanov:
> Richard,
> 
> On Tue, Jul 5, 2011 at 12:42 PM, Richard Weinberger <richard@....at> wrote:
> > Am Dienstag 05 Juli 2011, 01:15:47 schrieb Vitaliy Ivanov:
> >> From 7296c5b9770e95cd6ad4e9e71d2d14c972abdfe1 Mon Sep 17 00:00:00 2001
> >> From: Vitaliy Ivanov <vitalivanov@...il.com>
> >> Date: Tue, 5 Jul 2011 02:03:06 +0300
> >> Subject: [PATCH 2/4] uml: helper.c warning corrections
> >> MIME-Version: 1.0
> >> Content-Type: text/plain; charset=UTF-8
> >> Content-Transfer-Encoding: 8bit
> >> 
> >> arch/um/os-Linux/helper.c: In function ‘helper_child’:
> >> arch/um/os-Linux/helper.c:38:7: warning: ignoring return value of
> >> ‘write’, declared with attribute warn_unused_result
> > 
> > Same question as before...
> 
> Same answer is here:)
> 
> >> Signed-off-by: Vitaliy Ivanov <vitalivanov@...il.com>
> >> ---
> >>  arch/um/os-Linux/helper.c |    4 ++--
> >>  1 files changed, 2 insertions(+), 2 deletions(-)
> >> 
> >> diff --git a/arch/um/os-Linux/helper.c b/arch/um/os-Linux/helper.c
> >> index b6b1096..feff22d 100644
> >> --- a/arch/um/os-Linux/helper.c
> >> +++ b/arch/um/os-Linux/helper.c
> >> @@ -28,14 +28,14 @@ static int helper_child(void *arg)
> >>  {
> >>       struct helper_data *data = arg;
> >>       char **argv = data->argv;
> >> -     int err;
> >> +     int err, ret;
> >> 
> >>       if (data->pre_exec != NULL)
> >>               (*data->pre_exec)(data->pre_data);
> >>       err = execvp_noalloc(data->buf, argv[0], argv);
> >> 
> >>       /* If the exec succeeds, we don't get here */
> >> -     write(data->fd, &err, sizeof(err));
> >> +     CATCH_EINTR(ret = write(data->fd, &err, sizeof(err)));
> > 
> > Is there really a realistic chance that this write() can be interrupted?
> > helper_child() gets called via clone() in run_helper().
> 
> It's always better not to think whether it's possible but simply kill
> all the chances for this to happen.
> In this case that's pretty trivial thing and also it solves issue with
> warning.

Defensive programming is not a solution for everything.
CPU time and memory are not for free, especially in kernel land.

Anyway, when this patch removes a real warning, it's fine for me.
Applied.

Thanks,
//richard
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