linux-kernel - Re: [2.6.27.24] Kernel coredump to a pipe is failing

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Message-Id: <1243360869.29250.340.camel@psmith-ubeta.netezza.com>
Date:	Tue, 26 May 2009 14:01:09 -0400
From:	Paul Smith <paul@...-scientist.net>
To:	linux-kernel@...r.kernel.org
Subject: Re: [2.6.27.24] Kernel coredump to a pipe is failing

On Tue, 2009-05-26 at 12:33 -0400, Paul Smith wrote:
> Sorry for not following up to my previous message to get the threading
> headers correct: the original is on another system I don't have access
> to and I can't find a way to reply from any of the web archived
> versions.  Anyway, this is a link to the original FYI:
> 
> http://marc.info/?l=linux-kernel&m=124299629611706
> 
> In that post I observed that my short cores were being caused by
> dump_write() returning 0; taking another look at dump_write():
> 
>         static int dump_write(struct file *file, const void *addr, int nr)
>         {
>         	return file->f_op->write(file, addr, nr, &file->f_pos) == nr;
>         }
> 
> If the write operation returns an error of any kind, or it fails to
> write the complete set of bytes (nr here is always PAGE_SIZE, as this
> function is called when it fails), then dump_write() returns 0 and we
> get a short core.

I have verified that fs/pipe.c:pipe_write() is returning ERESTARTSYS as
a result of this code:

		if (signal_pending(current)) {
			if (!ret)
				ret = -ERESTARTSYS;
			break;
		}

I'm not exactly sure where to go from here, without knowing what the
design SHOULD be for signals that are received during core dumps.


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