linux-kernel - Re: REGRESSION: x86 vDSO: remove vdso-syms.o

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Date:	Mon, 11 Feb 2008 15:23:45 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Priit Laes <plaes@...es.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Sam Ravnborg <sam@...nborg.org>
Subject: Re: REGRESSION: x86 vDSO: remove vdso-syms.o

> if that file is empty, it might be the effect of a Ctrl-C. I sometimes 
> get that on .o files, if i Ctrl-C a highly parallel make -j at the wrong 
> moment. (is this expected behavior? It's been like this for a long 
> time.)

It is the known situation with the compiler since the dawn of time, yes.
It just writes the file directly, so if it dies in the middle, there's a
file with a fresh date.  For things like this done in makefile commands
with >, it has forever been canonical for the anal to use:

	... > $@...w
	mv -f $@...w $@

which avoids the problem.  The kernel makefiles are entirely haphazard
about places that do this or don't.  It uglifies the commands, but avoids
the problem of freshly-dated but wrong/empty files from botched make runs.
I did not do this in cmd_vdsosym (though I did in cmd_vdso32sym, go figure).

Thanks,
Roland
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