linux-kernel - Re: Unkillable R-state process stuck in sendfile

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Message-ID: <5304515A.8070809@parallels.com>
Date:	Wed, 19 Feb 2014 10:38:18 +0400
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	<Valdis.Kletnieks@...edu>
CC:	LKML <linux-kernel@...r.kernel.org>, Jan Kara <jack@...e.cz>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Unkillable R-state process stuck in sendfile

On 02/18/2014 11:13 PM, Valdis.Kletnieks@...edu wrote:
> On Mon, 17 Feb 2014 16:51:37 +0400, Vladimir Davydov said:
>
>>         out_fd = eventfd(0, 0);
>>         if (out_fd < 0)
>>                 err(1, "eventfd");
>>         ret = sendfile64(out_fd, in_fd, NULL, SIZE);
>> I'm not sure if this is actually bad and should be fixed, but perhaps
>> it's worth making do_generic_file_read() check for fatal signals pending
>> and break the read loop if so?
> Why do we even allow an eventfd to be fed to sendfile64 at all? What
> does that even *mean*?

I guess it's meaningless, so another fix (if this should be fixed at
all) would be disabling splice to eventfd. However, I cannot be
100%-sure nobody splices data to eventfd...

Thanks.
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