Re: [PATCH] tools/hotplug: fix locking

[Ian Campbell <Ian.Campbell@citrix.com>]

On Mon, 2012-06-11 at 14:59 +0100, Zhigang Wang wrote:
> This patch removes the ownner support and fixed this issue per my test.

I think the changelog here needs to go into a bit more detail about why
it is correct to remove the owner support. e.g. why is it no longer
needed or why is it bogus. Also why does removing it fix the issue?
Please describe the logic behind the change not just its impact on your
test case.

> Kouya: would you please help to confirm this fix is correct?
> 
> Anyone has encountered this issue please help to test.
> 
> Signed-off-by: Zhigang Wang <zhigang.x.wang@oracle.com>
> Cc: Kouya Shimura <kouya@jp.fujitsu.com>
> 
> diff -r 32034d1914a6 -r eb72d7090b59 tools/hotplug/Linux/locking.sh
> --- a/tools/hotplug/Linux/locking.sh	Thu Jun 07 19:46:57 2012 +0100
> +++ b/tools/hotplug/Linux/locking.sh	Mon Jun 11 09:29:43 2012 -0400
> @@ -48,32 +48,14 @@ sigerr() {
>  _claim_lock()
>  {
>    local lockdir="$1"
> -  local owner=$(_lock_owner "$lockdir")
>    local retries=0
>  
>    while [ $retries -lt $LOCK_RETRIES ]
>    do
> -    mkdir "$lockdir" 2>/dev/null && trap "_release_lock $lockdir; sigerr" ERR &&
> -      _update_lock_info "$lockdir" && return
> -
> -    local new_owner=$(_lock_owner "$lockdir")
> -    if [ "$new_owner" != "$owner" ]
> -    then
> -      owner="$new_owner"
> -      retries=0
> -    else
> -      local pid=$(echo $owner | cut -d : -f 1)
> -      if [ -n "$pid" -a "$pid" != "unknown" -a ! -f "/proc/$pid/status" ]
> -      then
> -        _release_lock $lockdir
> -      fi
> -    fi
> -
> +    mkdir "$lockdir" 2>/dev/null && trap "_release_lock $lockdir; sigerr" ERR && return
>      if [ $retries -gt $LOCK_SPINNING_RETRIES ]
>      then
>        sleep $LOCK_SLEEPTIME
> -    else
> -      sleep 0
>      fi
>      retries=$(($retries + 1))
>    done
> @@ -91,20 +73,7 @@ _release_lock()
>  _steal_lock()
>  {
>    local lockdir="$1"
> -  local owner=$(cat "$lockdir/owner" 2>/dev/null || echo "unknown")
> -  log err "Forced to steal lock on $lockdir from $owner!"
> +  log err "Forced to steal lock on $lockdir!"
>    _release_lock "$lockdir"
>    _claim_lock "$lockdir"
>  }
> -
> -
> -_lock_owner()
> -{
> -  cat "$1/owner" 2>/dev/null || echo "unknown"
> -}
> -
> -
> -_update_lock_info()
> -{
> -  echo "$$: $0" >"$1/owner"
> -}
> 
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