Insert into hold lock and never release.

I put following insert in a SP:

Insert into mytab(name, access_date,username, ipaddress )

     Select  'my name', getdate(), 'NA', ipaddr from master..sysprocesses where spid = @@spid   

.....

and then run pb app to call this SP. This cause a ex lock hold on table mytab and never release even auto commit =true in pb until I stop the app.

Not sure why. It is because of @@spid or master? how to release lock for this insert?