Re: [PATCH] kdumpctl: Run multiple kdumpctl instances one by one in serial order

[Dave Young]

On 08/30/13 at 05:21pm, WANG Chao wrote:
>  There will be a race condition if multiple kdumpctl instances are
>  running at the same time.
>  
>  By introducing a global mutex lock, only one instance can acquire this
>  lock and run, others will be waiting for the lock in queue. Now each
>  kdump instance will be run in serial order and there won't any race
>  condition.
>  
>  This is a patch backported from RHEL6.
>  
>  Signed-off-by: WANG Chao <chaowang(a)redhat.com&gt;
>  ---
>   kdumpctl | 9 +++++++++
>   1 file changed, 9 insertions(+)
>  
>  diff --git a/kdumpctl b/kdumpctl
>  index aba1e3c..d62b4b4 100755
>  --- a/kdumpctl
>  +++ b/kdumpctl
>  @@ -16,6 +16,12 @@ if [ -f /etc/sysconfig/kdump ]; then
>   	. /etc/sysconfig/kdump
>   fi
>   
>  +single_instance_lock()
>  +{
>  +	exec 9>/var/lock/kdump
>  +	flock 9
>  +}
>  +
>   # remove_cmdline_param <kernel cmdline> <param1> [<param2>] ...
> [<paramN>]
>   # Remove a list of kernel parameters from a given kernel cmdline and print the result.
>   # For each "arg" in the removing params list, "arg" and
> "arg=xxx" will be removed if exists.
>  @@ -531,6 +537,9 @@ if [ ! -f "$KDUMP_CONFIG_FILE" ]; then
>   	exit 1
>   fi
>   
>  +# Other kdumpctl instances will block in queue, until this one exits
>  +single_instance_lock
>  +
>   case "$1" in
>     start)
>   	if [ -s /proc/vmcore ]; then
>  -- 
>  1.8.3.1
>  
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Ack