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From: Andreas Schwab <schwab@suse.de>
To: Roland McGrath <roland@redhat.com>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>, 	Doug Evans <dje@google.com>, 	GDB Patches <gdb-patches@sourceware.org>, mark.kettenis@xs4all.nl
Subject: Re: [patch] Fix Linux attach to signalled/stopped processes
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Date: Wed, 24 Sep 2008 12:46:00 -0000
In-Reply-To: <20080414150919.GB32227@caradoc.them.org> (Daniel Jacobowitz's 	message of "Mon, 14 Apr 2008 11:09:19 -0400")
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Daniel Jacobowitz <drow@false.org> writes:

> +# Start the program running and then wait for a bit, to be sure
> +# that it can be attached to.
> +
> +set testpid [eval exec $binfile &]
> +
> +# No race
> +sleep 2
> +
> +# Do not: set testpid2 [expr $testpid + 1]
> +# as it will not exist on Red Hat 2.6.9-34.0.2.ELsmp
> +set testpid2 [expr $testpid + 2]
> +
> +set status2 /proc/${testpid}/task/${testpid2}/status
> +if {[expr ! [file exists $status2]]} {
> +  # kernel-2.4
> +  set status2 /proc/${testpid2}/status
> +}

There is no reason that this is required to work.  Even if pids are
allocated in increasing order there can be arbitrary other processes
created between the start of the process and the creation of its
threads.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
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"And now for something completely different."