On Sun, Jan 27, 2008 at 02:25:43PM -0600, Victor Lowther wrote:
> Adds a generic locking mechanism built around directory creation/removal.
> diff -U 0 -rNX diffignore pm-utils.updates/pm/functions working/pm/functions
> --- pm-utils.updates/pm/functions 2008-01-27 11:58:02.000000000 -0600
> +++ working/pm/functions 2008-01-27 11:26:51.000000000 -0600
> @@ -18,0 +18 @@
> +LOCKDIR="/tmp/.suspended"
> @@ -42,0 +38,33 @@
> +# try to take the lock. Fail if we cannot get it.
> +try_lock()
> +{
> + # $1 = directory to use as lock directory
> + # we use directory creation because the kernel enforces atomicity,
> + # and mkdir will fail if the directory already exists.
> + mkdir "$1" >/dev/null 2>&1 || return 1
> + return 0
> +}
> +
> +# spin waiting for the lock with optional timeout.
> +# return once we have it, or the timeout has expired
> +spin_lock()
> +{
> + # $1 = directory to use as the lock directory
> + # $2 = optional timeout
> + local elapsed=0
> + while ! try_lock $1; do
> + sleep 1;
> + [ "x$2" != "x" ] && [ $(( $elapsed == $2 )) -ne 0 ] && return 1
> + done
Does not work if timeout != 0.
--
Stefan Seyfried
R&D Team Mobile Devices | "Any ideas, John?"
SUSE LINUX Products GmbH, Nürnberg | "Well, surrounding them's out."
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