Where's the bug?

$1.$ bool withdraw$($double val$)\{$

$2.$ lock$()$;

$3.$ if$($account$\_$value $>=$ val$)\{$

$4.$ account$\_$value $-=$ val;

$5.$ unlock$()$;

$6.$ return true;

$7.\}$

$8.$ return false;

$9.\}$

No bug

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