soeventmtx
return (msleep_sbt(&sb->sb_acc, soeventmtx(so, which),
mtx_lock(soeventmtx(so, which))
mtx_unlock(soeventmtx(so, which))
mtx_assert(soeventmtx(so, which), MA_OWNED)
mtx_assert(soeventmtx(so, which), MA_NOTOWNED)